Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 1 | /* |
| 2 | * fs/userfaultfd.c |
| 3 | * |
| 4 | * Copyright (C) 2007 Davide Libenzi <davidel@xmailserver.org> |
| 5 | * Copyright (C) 2008-2009 Red Hat, Inc. |
| 6 | * Copyright (C) 2015 Red Hat, Inc. |
| 7 | * |
| 8 | * This work is licensed under the terms of the GNU GPL, version 2. See |
| 9 | * the COPYING file in the top-level directory. |
| 10 | * |
| 11 | * Some part derived from fs/eventfd.c (anon inode setup) and |
| 12 | * mm/ksm.c (mm hashing). |
| 13 | */ |
| 14 | |
Pavel Emelyanov | 9cd75c3 | 2017-02-22 15:42:21 -0800 | [diff] [blame] | 15 | #include <linux/list.h> |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 16 | #include <linux/hashtable.h> |
Ingo Molnar | 174cd4b | 2017-02-02 19:15:33 +0100 | [diff] [blame] | 17 | #include <linux/sched/signal.h> |
Ingo Molnar | 6e84f31 | 2017-02-08 18:51:29 +0100 | [diff] [blame] | 18 | #include <linux/sched/mm.h> |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 19 | #include <linux/mm.h> |
| 20 | #include <linux/poll.h> |
| 21 | #include <linux/slab.h> |
| 22 | #include <linux/seq_file.h> |
| 23 | #include <linux/file.h> |
| 24 | #include <linux/bug.h> |
| 25 | #include <linux/anon_inodes.h> |
| 26 | #include <linux/syscalls.h> |
| 27 | #include <linux/userfaultfd_k.h> |
| 28 | #include <linux/mempolicy.h> |
| 29 | #include <linux/ioctl.h> |
| 30 | #include <linux/security.h> |
Mike Kravetz | cab350a | 2017-02-22 15:43:04 -0800 | [diff] [blame] | 31 | #include <linux/hugetlb.h> |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 32 | |
Andrea Arcangeli | 3004ec9 | 2015-09-04 15:46:48 -0700 | [diff] [blame] | 33 | static struct kmem_cache *userfaultfd_ctx_cachep __read_mostly; |
| 34 | |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 35 | enum userfaultfd_state { |
| 36 | UFFD_STATE_WAIT_API, |
| 37 | UFFD_STATE_RUNNING, |
| 38 | }; |
| 39 | |
Andrea Arcangeli | 3004ec9 | 2015-09-04 15:46:48 -0700 | [diff] [blame] | 40 | /* |
| 41 | * Start with fault_pending_wqh and fault_wqh so they're more likely |
| 42 | * to be in the same cacheline. |
| 43 | */ |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 44 | struct userfaultfd_ctx { |
Andrea Arcangeli | 15b726e | 2015-09-04 15:46:44 -0700 | [diff] [blame] | 45 | /* waitqueue head for the pending (i.e. not read) userfaults */ |
| 46 | wait_queue_head_t fault_pending_wqh; |
| 47 | /* waitqueue head for the userfaults */ |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 48 | wait_queue_head_t fault_wqh; |
| 49 | /* waitqueue head for the pseudo fd to wakeup poll/read */ |
| 50 | wait_queue_head_t fd_wqh; |
Pavel Emelyanov | 9cd75c3 | 2017-02-22 15:42:21 -0800 | [diff] [blame] | 51 | /* waitqueue head for events */ |
| 52 | wait_queue_head_t event_wqh; |
Andrea Arcangeli | 2c5b7e1 | 2015-09-04 15:47:23 -0700 | [diff] [blame] | 53 | /* a refile sequence protected by fault_pending_wqh lock */ |
| 54 | struct seqcount refile_seq; |
Andrea Arcangeli | 3004ec9 | 2015-09-04 15:46:48 -0700 | [diff] [blame] | 55 | /* pseudo fd refcounting */ |
| 56 | atomic_t refcount; |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 57 | /* userfaultfd syscall flags */ |
| 58 | unsigned int flags; |
Pavel Emelyanov | 9cd75c3 | 2017-02-22 15:42:21 -0800 | [diff] [blame] | 59 | /* features requested from the userspace */ |
| 60 | unsigned int features; |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 61 | /* state machine */ |
| 62 | enum userfaultfd_state state; |
| 63 | /* released */ |
| 64 | bool released; |
| 65 | /* mm with one ore more vmas attached to this userfaultfd_ctx */ |
| 66 | struct mm_struct *mm; |
| 67 | }; |
| 68 | |
Pavel Emelyanov | 893e26e | 2017-02-22 15:42:27 -0800 | [diff] [blame] | 69 | struct userfaultfd_fork_ctx { |
| 70 | struct userfaultfd_ctx *orig; |
| 71 | struct userfaultfd_ctx *new; |
| 72 | struct list_head list; |
| 73 | }; |
| 74 | |
Mike Rapoport | 897ab3e | 2017-02-24 14:58:22 -0800 | [diff] [blame] | 75 | struct userfaultfd_unmap_ctx { |
| 76 | struct userfaultfd_ctx *ctx; |
| 77 | unsigned long start; |
| 78 | unsigned long end; |
| 79 | struct list_head list; |
| 80 | }; |
| 81 | |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 82 | struct userfaultfd_wait_queue { |
Andrea Arcangeli | a9b85f9 | 2015-09-04 15:46:37 -0700 | [diff] [blame] | 83 | struct uffd_msg msg; |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 84 | wait_queue_t wq; |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 85 | struct userfaultfd_ctx *ctx; |
Andrea Arcangeli | 15a77c6 | 2017-01-24 15:17:59 -0800 | [diff] [blame] | 86 | bool waken; |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 87 | }; |
| 88 | |
| 89 | struct userfaultfd_wake_range { |
| 90 | unsigned long start; |
| 91 | unsigned long len; |
| 92 | }; |
| 93 | |
| 94 | static int userfaultfd_wake_function(wait_queue_t *wq, unsigned mode, |
| 95 | int wake_flags, void *key) |
| 96 | { |
| 97 | struct userfaultfd_wake_range *range = key; |
| 98 | int ret; |
| 99 | struct userfaultfd_wait_queue *uwq; |
| 100 | unsigned long start, len; |
| 101 | |
| 102 | uwq = container_of(wq, struct userfaultfd_wait_queue, wq); |
| 103 | ret = 0; |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 104 | /* len == 0 means wake all */ |
| 105 | start = range->start; |
| 106 | len = range->len; |
Andrea Arcangeli | a9b85f9 | 2015-09-04 15:46:37 -0700 | [diff] [blame] | 107 | if (len && (start > uwq->msg.arg.pagefault.address || |
| 108 | start + len <= uwq->msg.arg.pagefault.address)) |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 109 | goto out; |
Andrea Arcangeli | 15a77c6 | 2017-01-24 15:17:59 -0800 | [diff] [blame] | 110 | WRITE_ONCE(uwq->waken, true); |
| 111 | /* |
| 112 | * The implicit smp_mb__before_spinlock in try_to_wake_up() |
| 113 | * renders uwq->waken visible to other CPUs before the task is |
| 114 | * waken. |
| 115 | */ |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 116 | ret = wake_up_state(wq->private, mode); |
| 117 | if (ret) |
| 118 | /* |
| 119 | * Wake only once, autoremove behavior. |
| 120 | * |
| 121 | * After the effect of list_del_init is visible to the |
| 122 | * other CPUs, the waitqueue may disappear from under |
| 123 | * us, see the !list_empty_careful() in |
| 124 | * handle_userfault(). try_to_wake_up() has an |
| 125 | * implicit smp_mb__before_spinlock, and the |
| 126 | * wq->private is read before calling the extern |
| 127 | * function "wake_up_state" (which in turns calls |
| 128 | * try_to_wake_up). While the spin_lock;spin_unlock; |
| 129 | * wouldn't be enough, the smp_mb__before_spinlock is |
| 130 | * enough to avoid an explicit smp_mb() here. |
| 131 | */ |
| 132 | list_del_init(&wq->task_list); |
| 133 | out: |
| 134 | return ret; |
| 135 | } |
| 136 | |
| 137 | /** |
| 138 | * userfaultfd_ctx_get - Acquires a reference to the internal userfaultfd |
| 139 | * context. |
| 140 | * @ctx: [in] Pointer to the userfaultfd context. |
| 141 | * |
| 142 | * Returns: In case of success, returns not zero. |
| 143 | */ |
| 144 | static void userfaultfd_ctx_get(struct userfaultfd_ctx *ctx) |
| 145 | { |
| 146 | if (!atomic_inc_not_zero(&ctx->refcount)) |
| 147 | BUG(); |
| 148 | } |
| 149 | |
| 150 | /** |
| 151 | * userfaultfd_ctx_put - Releases a reference to the internal userfaultfd |
| 152 | * context. |
| 153 | * @ctx: [in] Pointer to userfaultfd context. |
| 154 | * |
| 155 | * The userfaultfd context reference must have been previously acquired either |
| 156 | * with userfaultfd_ctx_get() or userfaultfd_ctx_fdget(). |
| 157 | */ |
| 158 | static void userfaultfd_ctx_put(struct userfaultfd_ctx *ctx) |
| 159 | { |
| 160 | if (atomic_dec_and_test(&ctx->refcount)) { |
| 161 | VM_BUG_ON(spin_is_locked(&ctx->fault_pending_wqh.lock)); |
| 162 | VM_BUG_ON(waitqueue_active(&ctx->fault_pending_wqh)); |
| 163 | VM_BUG_ON(spin_is_locked(&ctx->fault_wqh.lock)); |
| 164 | VM_BUG_ON(waitqueue_active(&ctx->fault_wqh)); |
Pavel Emelyanov | 9cd75c3 | 2017-02-22 15:42:21 -0800 | [diff] [blame] | 165 | VM_BUG_ON(spin_is_locked(&ctx->event_wqh.lock)); |
| 166 | VM_BUG_ON(waitqueue_active(&ctx->event_wqh)); |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 167 | VM_BUG_ON(spin_is_locked(&ctx->fd_wqh.lock)); |
| 168 | VM_BUG_ON(waitqueue_active(&ctx->fd_wqh)); |
Oleg Nesterov | d2005e3 | 2016-05-20 16:58:36 -0700 | [diff] [blame] | 169 | mmdrop(ctx->mm); |
Andrea Arcangeli | 3004ec9 | 2015-09-04 15:46:48 -0700 | [diff] [blame] | 170 | kmem_cache_free(userfaultfd_ctx_cachep, ctx); |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 171 | } |
| 172 | } |
| 173 | |
Andrea Arcangeli | a9b85f9 | 2015-09-04 15:46:37 -0700 | [diff] [blame] | 174 | static inline void msg_init(struct uffd_msg *msg) |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 175 | { |
Andrea Arcangeli | a9b85f9 | 2015-09-04 15:46:37 -0700 | [diff] [blame] | 176 | BUILD_BUG_ON(sizeof(struct uffd_msg) != 32); |
| 177 | /* |
| 178 | * Must use memset to zero out the paddings or kernel data is |
| 179 | * leaked to userland. |
| 180 | */ |
| 181 | memset(msg, 0, sizeof(struct uffd_msg)); |
| 182 | } |
| 183 | |
| 184 | static inline struct uffd_msg userfault_msg(unsigned long address, |
| 185 | unsigned int flags, |
| 186 | unsigned long reason) |
| 187 | { |
| 188 | struct uffd_msg msg; |
| 189 | msg_init(&msg); |
| 190 | msg.event = UFFD_EVENT_PAGEFAULT; |
| 191 | msg.arg.pagefault.address = address; |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 192 | if (flags & FAULT_FLAG_WRITE) |
| 193 | /* |
Andrea Arcangeli | a4605a6 | 2017-02-22 15:42:09 -0800 | [diff] [blame] | 194 | * If UFFD_FEATURE_PAGEFAULT_FLAG_WP was set in the |
Andrea Arcangeli | a9b85f9 | 2015-09-04 15:46:37 -0700 | [diff] [blame] | 195 | * uffdio_api.features and UFFD_PAGEFAULT_FLAG_WRITE |
| 196 | * was not set in a UFFD_EVENT_PAGEFAULT, it means it |
| 197 | * was a read fault, otherwise if set it means it's |
| 198 | * a write fault. |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 199 | */ |
Andrea Arcangeli | a9b85f9 | 2015-09-04 15:46:37 -0700 | [diff] [blame] | 200 | msg.arg.pagefault.flags |= UFFD_PAGEFAULT_FLAG_WRITE; |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 201 | if (reason & VM_UFFD_WP) |
| 202 | /* |
Andrea Arcangeli | a9b85f9 | 2015-09-04 15:46:37 -0700 | [diff] [blame] | 203 | * If UFFD_FEATURE_PAGEFAULT_FLAG_WP was set in the |
| 204 | * uffdio_api.features and UFFD_PAGEFAULT_FLAG_WP was |
| 205 | * not set in a UFFD_EVENT_PAGEFAULT, it means it was |
| 206 | * a missing fault, otherwise if set it means it's a |
| 207 | * write protect fault. |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 208 | */ |
Andrea Arcangeli | a9b85f9 | 2015-09-04 15:46:37 -0700 | [diff] [blame] | 209 | msg.arg.pagefault.flags |= UFFD_PAGEFAULT_FLAG_WP; |
| 210 | return msg; |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 211 | } |
| 212 | |
Mike Kravetz | 369cd21 | 2017-02-22 15:43:10 -0800 | [diff] [blame] | 213 | #ifdef CONFIG_HUGETLB_PAGE |
| 214 | /* |
| 215 | * Same functionality as userfaultfd_must_wait below with modifications for |
| 216 | * hugepmd ranges. |
| 217 | */ |
| 218 | static inline bool userfaultfd_huge_must_wait(struct userfaultfd_ctx *ctx, |
| 219 | unsigned long address, |
| 220 | unsigned long flags, |
| 221 | unsigned long reason) |
| 222 | { |
| 223 | struct mm_struct *mm = ctx->mm; |
| 224 | pte_t *pte; |
| 225 | bool ret = true; |
| 226 | |
| 227 | VM_BUG_ON(!rwsem_is_locked(&mm->mmap_sem)); |
| 228 | |
| 229 | pte = huge_pte_offset(mm, address); |
| 230 | if (!pte) |
| 231 | goto out; |
| 232 | |
| 233 | ret = false; |
| 234 | |
| 235 | /* |
| 236 | * Lockless access: we're in a wait_event so it's ok if it |
| 237 | * changes under us. |
| 238 | */ |
| 239 | if (huge_pte_none(*pte)) |
| 240 | ret = true; |
| 241 | if (!huge_pte_write(*pte) && (reason & VM_UFFD_WP)) |
| 242 | ret = true; |
| 243 | out: |
| 244 | return ret; |
| 245 | } |
| 246 | #else |
| 247 | static inline bool userfaultfd_huge_must_wait(struct userfaultfd_ctx *ctx, |
| 248 | unsigned long address, |
| 249 | unsigned long flags, |
| 250 | unsigned long reason) |
| 251 | { |
| 252 | return false; /* should never get here */ |
| 253 | } |
| 254 | #endif /* CONFIG_HUGETLB_PAGE */ |
| 255 | |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 256 | /* |
Andrea Arcangeli | 8d2afd9 | 2015-09-04 15:46:51 -0700 | [diff] [blame] | 257 | * Verify the pagetables are still not ok after having reigstered into |
| 258 | * the fault_pending_wqh to avoid userland having to UFFDIO_WAKE any |
| 259 | * userfault that has already been resolved, if userfaultfd_read and |
| 260 | * UFFDIO_COPY|ZEROPAGE are being run simultaneously on two different |
| 261 | * threads. |
| 262 | */ |
| 263 | static inline bool userfaultfd_must_wait(struct userfaultfd_ctx *ctx, |
| 264 | unsigned long address, |
| 265 | unsigned long flags, |
| 266 | unsigned long reason) |
| 267 | { |
| 268 | struct mm_struct *mm = ctx->mm; |
| 269 | pgd_t *pgd; |
| 270 | pud_t *pud; |
| 271 | pmd_t *pmd, _pmd; |
| 272 | pte_t *pte; |
| 273 | bool ret = true; |
| 274 | |
| 275 | VM_BUG_ON(!rwsem_is_locked(&mm->mmap_sem)); |
| 276 | |
| 277 | pgd = pgd_offset(mm, address); |
| 278 | if (!pgd_present(*pgd)) |
| 279 | goto out; |
| 280 | pud = pud_offset(pgd, address); |
| 281 | if (!pud_present(*pud)) |
| 282 | goto out; |
| 283 | pmd = pmd_offset(pud, address); |
| 284 | /* |
| 285 | * READ_ONCE must function as a barrier with narrower scope |
| 286 | * and it must be equivalent to: |
| 287 | * _pmd = *pmd; barrier(); |
| 288 | * |
| 289 | * This is to deal with the instability (as in |
| 290 | * pmd_trans_unstable) of the pmd. |
| 291 | */ |
| 292 | _pmd = READ_ONCE(*pmd); |
| 293 | if (!pmd_present(_pmd)) |
| 294 | goto out; |
| 295 | |
| 296 | ret = false; |
| 297 | if (pmd_trans_huge(_pmd)) |
| 298 | goto out; |
| 299 | |
| 300 | /* |
| 301 | * the pmd is stable (as in !pmd_trans_unstable) so we can re-read it |
| 302 | * and use the standard pte_offset_map() instead of parsing _pmd. |
| 303 | */ |
| 304 | pte = pte_offset_map(pmd, address); |
| 305 | /* |
| 306 | * Lockless access: we're in a wait_event so it's ok if it |
| 307 | * changes under us. |
| 308 | */ |
| 309 | if (pte_none(*pte)) |
| 310 | ret = true; |
| 311 | pte_unmap(pte); |
| 312 | |
| 313 | out: |
| 314 | return ret; |
| 315 | } |
| 316 | |
| 317 | /* |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 318 | * The locking rules involved in returning VM_FAULT_RETRY depending on |
| 319 | * FAULT_FLAG_ALLOW_RETRY, FAULT_FLAG_RETRY_NOWAIT and |
| 320 | * FAULT_FLAG_KILLABLE are not straightforward. The "Caution" |
| 321 | * recommendation in __lock_page_or_retry is not an understatement. |
| 322 | * |
| 323 | * If FAULT_FLAG_ALLOW_RETRY is set, the mmap_sem must be released |
| 324 | * before returning VM_FAULT_RETRY only if FAULT_FLAG_RETRY_NOWAIT is |
| 325 | * not set. |
| 326 | * |
| 327 | * If FAULT_FLAG_ALLOW_RETRY is set but FAULT_FLAG_KILLABLE is not |
| 328 | * set, VM_FAULT_RETRY can still be returned if and only if there are |
| 329 | * fatal_signal_pending()s, and the mmap_sem must be released before |
| 330 | * returning it. |
| 331 | */ |
Jan Kara | 82b0f8c | 2016-12-14 15:06:58 -0800 | [diff] [blame] | 332 | int handle_userfault(struct vm_fault *vmf, unsigned long reason) |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 333 | { |
Jan Kara | 82b0f8c | 2016-12-14 15:06:58 -0800 | [diff] [blame] | 334 | struct mm_struct *mm = vmf->vma->vm_mm; |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 335 | struct userfaultfd_ctx *ctx; |
| 336 | struct userfaultfd_wait_queue uwq; |
Andrea Arcangeli | ba85c70 | 2015-09-04 15:46:41 -0700 | [diff] [blame] | 337 | int ret; |
Andrea Arcangeli | dfa37dc | 2015-09-04 15:47:18 -0700 | [diff] [blame] | 338 | bool must_wait, return_to_userland; |
Andrea Arcangeli | 15a77c6 | 2017-01-24 15:17:59 -0800 | [diff] [blame] | 339 | long blocking_state; |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 340 | |
| 341 | BUG_ON(!rwsem_is_locked(&mm->mmap_sem)); |
| 342 | |
Andrea Arcangeli | ba85c70 | 2015-09-04 15:46:41 -0700 | [diff] [blame] | 343 | ret = VM_FAULT_SIGBUS; |
Jan Kara | 82b0f8c | 2016-12-14 15:06:58 -0800 | [diff] [blame] | 344 | ctx = vmf->vma->vm_userfaultfd_ctx.ctx; |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 345 | if (!ctx) |
Andrea Arcangeli | ba85c70 | 2015-09-04 15:46:41 -0700 | [diff] [blame] | 346 | goto out; |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 347 | |
| 348 | BUG_ON(ctx->mm != mm); |
| 349 | |
| 350 | VM_BUG_ON(reason & ~(VM_UFFD_MISSING|VM_UFFD_WP)); |
| 351 | VM_BUG_ON(!(reason & VM_UFFD_MISSING) ^ !!(reason & VM_UFFD_WP)); |
| 352 | |
| 353 | /* |
| 354 | * If it's already released don't get it. This avoids to loop |
| 355 | * in __get_user_pages if userfaultfd_release waits on the |
| 356 | * caller of handle_userfault to release the mmap_sem. |
| 357 | */ |
| 358 | if (unlikely(ACCESS_ONCE(ctx->released))) |
Andrea Arcangeli | ba85c70 | 2015-09-04 15:46:41 -0700 | [diff] [blame] | 359 | goto out; |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 360 | |
| 361 | /* |
Linus Torvalds | 39680f5 | 2016-03-01 11:56:22 -0800 | [diff] [blame] | 362 | * We don't do userfault handling for the final child pid update. |
| 363 | */ |
| 364 | if (current->flags & PF_EXITING) |
| 365 | goto out; |
| 366 | |
| 367 | /* |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 368 | * Check that we can return VM_FAULT_RETRY. |
| 369 | * |
| 370 | * NOTE: it should become possible to return VM_FAULT_RETRY |
| 371 | * even if FAULT_FLAG_TRIED is set without leading to gup() |
| 372 | * -EBUSY failures, if the userfaultfd is to be extended for |
| 373 | * VM_UFFD_WP tracking and we intend to arm the userfault |
| 374 | * without first stopping userland access to the memory. For |
| 375 | * VM_UFFD_MISSING userfaults this is enough for now. |
| 376 | */ |
Jan Kara | 82b0f8c | 2016-12-14 15:06:58 -0800 | [diff] [blame] | 377 | if (unlikely(!(vmf->flags & FAULT_FLAG_ALLOW_RETRY))) { |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 378 | /* |
| 379 | * Validate the invariant that nowait must allow retry |
| 380 | * to be sure not to return SIGBUS erroneously on |
| 381 | * nowait invocations. |
| 382 | */ |
Jan Kara | 82b0f8c | 2016-12-14 15:06:58 -0800 | [diff] [blame] | 383 | BUG_ON(vmf->flags & FAULT_FLAG_RETRY_NOWAIT); |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 384 | #ifdef CONFIG_DEBUG_VM |
| 385 | if (printk_ratelimit()) { |
| 386 | printk(KERN_WARNING |
Jan Kara | 82b0f8c | 2016-12-14 15:06:58 -0800 | [diff] [blame] | 387 | "FAULT_FLAG_ALLOW_RETRY missing %x\n", |
| 388 | vmf->flags); |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 389 | dump_stack(); |
| 390 | } |
| 391 | #endif |
Andrea Arcangeli | ba85c70 | 2015-09-04 15:46:41 -0700 | [diff] [blame] | 392 | goto out; |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 393 | } |
| 394 | |
| 395 | /* |
| 396 | * Handle nowait, not much to do other than tell it to retry |
| 397 | * and wait. |
| 398 | */ |
Andrea Arcangeli | ba85c70 | 2015-09-04 15:46:41 -0700 | [diff] [blame] | 399 | ret = VM_FAULT_RETRY; |
Jan Kara | 82b0f8c | 2016-12-14 15:06:58 -0800 | [diff] [blame] | 400 | if (vmf->flags & FAULT_FLAG_RETRY_NOWAIT) |
Andrea Arcangeli | ba85c70 | 2015-09-04 15:46:41 -0700 | [diff] [blame] | 401 | goto out; |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 402 | |
| 403 | /* take the reference before dropping the mmap_sem */ |
| 404 | userfaultfd_ctx_get(ctx); |
| 405 | |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 406 | init_waitqueue_func_entry(&uwq.wq, userfaultfd_wake_function); |
| 407 | uwq.wq.private = current; |
Jan Kara | 82b0f8c | 2016-12-14 15:06:58 -0800 | [diff] [blame] | 408 | uwq.msg = userfault_msg(vmf->address, vmf->flags, reason); |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 409 | uwq.ctx = ctx; |
Andrea Arcangeli | 15a77c6 | 2017-01-24 15:17:59 -0800 | [diff] [blame] | 410 | uwq.waken = false; |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 411 | |
Kirill A. Shutemov | bae473a | 2016-07-26 15:25:20 -0700 | [diff] [blame] | 412 | return_to_userland = |
Jan Kara | 82b0f8c | 2016-12-14 15:06:58 -0800 | [diff] [blame] | 413 | (vmf->flags & (FAULT_FLAG_USER|FAULT_FLAG_KILLABLE)) == |
Andrea Arcangeli | dfa37dc | 2015-09-04 15:47:18 -0700 | [diff] [blame] | 414 | (FAULT_FLAG_USER|FAULT_FLAG_KILLABLE); |
Andrea Arcangeli | 15a77c6 | 2017-01-24 15:17:59 -0800 | [diff] [blame] | 415 | blocking_state = return_to_userland ? TASK_INTERRUPTIBLE : |
| 416 | TASK_KILLABLE; |
Andrea Arcangeli | dfa37dc | 2015-09-04 15:47:18 -0700 | [diff] [blame] | 417 | |
Andrea Arcangeli | 15b726e | 2015-09-04 15:46:44 -0700 | [diff] [blame] | 418 | spin_lock(&ctx->fault_pending_wqh.lock); |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 419 | /* |
| 420 | * After the __add_wait_queue the uwq is visible to userland |
| 421 | * through poll/read(). |
| 422 | */ |
Andrea Arcangeli | 15b726e | 2015-09-04 15:46:44 -0700 | [diff] [blame] | 423 | __add_wait_queue(&ctx->fault_pending_wqh, &uwq.wq); |
| 424 | /* |
| 425 | * The smp_mb() after __set_current_state prevents the reads |
| 426 | * following the spin_unlock to happen before the list_add in |
| 427 | * __add_wait_queue. |
| 428 | */ |
Andrea Arcangeli | 15a77c6 | 2017-01-24 15:17:59 -0800 | [diff] [blame] | 429 | set_current_state(blocking_state); |
Andrea Arcangeli | 15b726e | 2015-09-04 15:46:44 -0700 | [diff] [blame] | 430 | spin_unlock(&ctx->fault_pending_wqh.lock); |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 431 | |
Mike Kravetz | 369cd21 | 2017-02-22 15:43:10 -0800 | [diff] [blame] | 432 | if (!is_vm_hugetlb_page(vmf->vma)) |
| 433 | must_wait = userfaultfd_must_wait(ctx, vmf->address, vmf->flags, |
| 434 | reason); |
| 435 | else |
| 436 | must_wait = userfaultfd_huge_must_wait(ctx, vmf->address, |
| 437 | vmf->flags, reason); |
Andrea Arcangeli | 8d2afd9 | 2015-09-04 15:46:51 -0700 | [diff] [blame] | 438 | up_read(&mm->mmap_sem); |
| 439 | |
| 440 | if (likely(must_wait && !ACCESS_ONCE(ctx->released) && |
Andrea Arcangeli | dfa37dc | 2015-09-04 15:47:18 -0700 | [diff] [blame] | 441 | (return_to_userland ? !signal_pending(current) : |
| 442 | !fatal_signal_pending(current)))) { |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 443 | wake_up_poll(&ctx->fd_wqh, POLLIN); |
| 444 | schedule(); |
Andrea Arcangeli | ba85c70 | 2015-09-04 15:46:41 -0700 | [diff] [blame] | 445 | ret |= VM_FAULT_MAJOR; |
Andrea Arcangeli | 15a77c6 | 2017-01-24 15:17:59 -0800 | [diff] [blame] | 446 | |
| 447 | /* |
| 448 | * False wakeups can orginate even from rwsem before |
| 449 | * up_read() however userfaults will wait either for a |
| 450 | * targeted wakeup on the specific uwq waitqueue from |
| 451 | * wake_userfault() or for signals or for uffd |
| 452 | * release. |
| 453 | */ |
| 454 | while (!READ_ONCE(uwq.waken)) { |
| 455 | /* |
| 456 | * This needs the full smp_store_mb() |
| 457 | * guarantee as the state write must be |
| 458 | * visible to other CPUs before reading |
| 459 | * uwq.waken from other CPUs. |
| 460 | */ |
| 461 | set_current_state(blocking_state); |
| 462 | if (READ_ONCE(uwq.waken) || |
| 463 | READ_ONCE(ctx->released) || |
| 464 | (return_to_userland ? signal_pending(current) : |
| 465 | fatal_signal_pending(current))) |
| 466 | break; |
| 467 | schedule(); |
| 468 | } |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 469 | } |
Andrea Arcangeli | ba85c70 | 2015-09-04 15:46:41 -0700 | [diff] [blame] | 470 | |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 471 | __set_current_state(TASK_RUNNING); |
Andrea Arcangeli | 15b726e | 2015-09-04 15:46:44 -0700 | [diff] [blame] | 472 | |
Andrea Arcangeli | dfa37dc | 2015-09-04 15:47:18 -0700 | [diff] [blame] | 473 | if (return_to_userland) { |
| 474 | if (signal_pending(current) && |
| 475 | !fatal_signal_pending(current)) { |
| 476 | /* |
| 477 | * If we got a SIGSTOP or SIGCONT and this is |
| 478 | * a normal userland page fault, just let |
| 479 | * userland return so the signal will be |
| 480 | * handled and gdb debugging works. The page |
| 481 | * fault code immediately after we return from |
| 482 | * this function is going to release the |
| 483 | * mmap_sem and it's not depending on it |
| 484 | * (unlike gup would if we were not to return |
| 485 | * VM_FAULT_RETRY). |
| 486 | * |
| 487 | * If a fatal signal is pending we still take |
| 488 | * the streamlined VM_FAULT_RETRY failure path |
| 489 | * and there's no need to retake the mmap_sem |
| 490 | * in such case. |
| 491 | */ |
| 492 | down_read(&mm->mmap_sem); |
| 493 | ret = 0; |
| 494 | } |
| 495 | } |
| 496 | |
Andrea Arcangeli | 15b726e | 2015-09-04 15:46:44 -0700 | [diff] [blame] | 497 | /* |
| 498 | * Here we race with the list_del; list_add in |
| 499 | * userfaultfd_ctx_read(), however because we don't ever run |
| 500 | * list_del_init() to refile across the two lists, the prev |
| 501 | * and next pointers will never point to self. list_add also |
| 502 | * would never let any of the two pointers to point to |
| 503 | * self. So list_empty_careful won't risk to see both pointers |
| 504 | * pointing to self at any time during the list refile. The |
| 505 | * only case where list_del_init() is called is the full |
| 506 | * removal in the wake function and there we don't re-list_add |
| 507 | * and it's fine not to block on the spinlock. The uwq on this |
| 508 | * kernel stack can be released after the list_del_init. |
| 509 | */ |
Andrea Arcangeli | ba85c70 | 2015-09-04 15:46:41 -0700 | [diff] [blame] | 510 | if (!list_empty_careful(&uwq.wq.task_list)) { |
Andrea Arcangeli | 15b726e | 2015-09-04 15:46:44 -0700 | [diff] [blame] | 511 | spin_lock(&ctx->fault_pending_wqh.lock); |
| 512 | /* |
| 513 | * No need of list_del_init(), the uwq on the stack |
| 514 | * will be freed shortly anyway. |
| 515 | */ |
| 516 | list_del(&uwq.wq.task_list); |
| 517 | spin_unlock(&ctx->fault_pending_wqh.lock); |
Andrea Arcangeli | ba85c70 | 2015-09-04 15:46:41 -0700 | [diff] [blame] | 518 | } |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 519 | |
| 520 | /* |
| 521 | * ctx may go away after this if the userfault pseudo fd is |
| 522 | * already released. |
| 523 | */ |
| 524 | userfaultfd_ctx_put(ctx); |
| 525 | |
Andrea Arcangeli | ba85c70 | 2015-09-04 15:46:41 -0700 | [diff] [blame] | 526 | out: |
| 527 | return ret; |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 528 | } |
| 529 | |
Pavel Emelyanov | 893e26e | 2017-02-22 15:42:27 -0800 | [diff] [blame] | 530 | static int userfaultfd_event_wait_completion(struct userfaultfd_ctx *ctx, |
| 531 | struct userfaultfd_wait_queue *ewq) |
Pavel Emelyanov | 9cd75c3 | 2017-02-22 15:42:21 -0800 | [diff] [blame] | 532 | { |
| 533 | int ret = 0; |
| 534 | |
| 535 | ewq->ctx = ctx; |
| 536 | init_waitqueue_entry(&ewq->wq, current); |
| 537 | |
| 538 | spin_lock(&ctx->event_wqh.lock); |
| 539 | /* |
| 540 | * After the __add_wait_queue the uwq is visible to userland |
| 541 | * through poll/read(). |
| 542 | */ |
| 543 | __add_wait_queue(&ctx->event_wqh, &ewq->wq); |
| 544 | for (;;) { |
| 545 | set_current_state(TASK_KILLABLE); |
| 546 | if (ewq->msg.event == 0) |
| 547 | break; |
| 548 | if (ACCESS_ONCE(ctx->released) || |
| 549 | fatal_signal_pending(current)) { |
| 550 | ret = -1; |
| 551 | __remove_wait_queue(&ctx->event_wqh, &ewq->wq); |
| 552 | break; |
| 553 | } |
| 554 | |
| 555 | spin_unlock(&ctx->event_wqh.lock); |
| 556 | |
| 557 | wake_up_poll(&ctx->fd_wqh, POLLIN); |
| 558 | schedule(); |
| 559 | |
| 560 | spin_lock(&ctx->event_wqh.lock); |
| 561 | } |
| 562 | __set_current_state(TASK_RUNNING); |
| 563 | spin_unlock(&ctx->event_wqh.lock); |
| 564 | |
| 565 | /* |
| 566 | * ctx may go away after this if the userfault pseudo fd is |
| 567 | * already released. |
| 568 | */ |
| 569 | |
| 570 | userfaultfd_ctx_put(ctx); |
| 571 | return ret; |
| 572 | } |
| 573 | |
| 574 | static void userfaultfd_event_complete(struct userfaultfd_ctx *ctx, |
| 575 | struct userfaultfd_wait_queue *ewq) |
| 576 | { |
| 577 | ewq->msg.event = 0; |
| 578 | wake_up_locked(&ctx->event_wqh); |
| 579 | __remove_wait_queue(&ctx->event_wqh, &ewq->wq); |
| 580 | } |
| 581 | |
Pavel Emelyanov | 893e26e | 2017-02-22 15:42:27 -0800 | [diff] [blame] | 582 | int dup_userfaultfd(struct vm_area_struct *vma, struct list_head *fcs) |
| 583 | { |
| 584 | struct userfaultfd_ctx *ctx = NULL, *octx; |
| 585 | struct userfaultfd_fork_ctx *fctx; |
| 586 | |
| 587 | octx = vma->vm_userfaultfd_ctx.ctx; |
| 588 | if (!octx || !(octx->features & UFFD_FEATURE_EVENT_FORK)) { |
| 589 | vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX; |
| 590 | vma->vm_flags &= ~(VM_UFFD_WP | VM_UFFD_MISSING); |
| 591 | return 0; |
| 592 | } |
| 593 | |
| 594 | list_for_each_entry(fctx, fcs, list) |
| 595 | if (fctx->orig == octx) { |
| 596 | ctx = fctx->new; |
| 597 | break; |
| 598 | } |
| 599 | |
| 600 | if (!ctx) { |
| 601 | fctx = kmalloc(sizeof(*fctx), GFP_KERNEL); |
| 602 | if (!fctx) |
| 603 | return -ENOMEM; |
| 604 | |
| 605 | ctx = kmem_cache_alloc(userfaultfd_ctx_cachep, GFP_KERNEL); |
| 606 | if (!ctx) { |
| 607 | kfree(fctx); |
| 608 | return -ENOMEM; |
| 609 | } |
| 610 | |
| 611 | atomic_set(&ctx->refcount, 1); |
| 612 | ctx->flags = octx->flags; |
| 613 | ctx->state = UFFD_STATE_RUNNING; |
| 614 | ctx->features = octx->features; |
| 615 | ctx->released = false; |
| 616 | ctx->mm = vma->vm_mm; |
Mike Rapoport | d3aadc8 | 2017-02-22 15:42:30 -0800 | [diff] [blame] | 617 | atomic_inc(&ctx->mm->mm_count); |
Pavel Emelyanov | 893e26e | 2017-02-22 15:42:27 -0800 | [diff] [blame] | 618 | |
| 619 | userfaultfd_ctx_get(octx); |
| 620 | fctx->orig = octx; |
| 621 | fctx->new = ctx; |
| 622 | list_add_tail(&fctx->list, fcs); |
| 623 | } |
| 624 | |
| 625 | vma->vm_userfaultfd_ctx.ctx = ctx; |
| 626 | return 0; |
| 627 | } |
| 628 | |
| 629 | static int dup_fctx(struct userfaultfd_fork_ctx *fctx) |
| 630 | { |
| 631 | struct userfaultfd_ctx *ctx = fctx->orig; |
| 632 | struct userfaultfd_wait_queue ewq; |
| 633 | |
| 634 | msg_init(&ewq.msg); |
| 635 | |
| 636 | ewq.msg.event = UFFD_EVENT_FORK; |
| 637 | ewq.msg.arg.reserved.reserved1 = (unsigned long)fctx->new; |
| 638 | |
| 639 | return userfaultfd_event_wait_completion(ctx, &ewq); |
| 640 | } |
| 641 | |
| 642 | void dup_userfaultfd_complete(struct list_head *fcs) |
| 643 | { |
| 644 | int ret = 0; |
| 645 | struct userfaultfd_fork_ctx *fctx, *n; |
| 646 | |
| 647 | list_for_each_entry_safe(fctx, n, fcs, list) { |
| 648 | if (!ret) |
| 649 | ret = dup_fctx(fctx); |
| 650 | list_del(&fctx->list); |
| 651 | kfree(fctx); |
| 652 | } |
| 653 | } |
| 654 | |
Pavel Emelyanov | 72f8765 | 2017-02-22 15:42:34 -0800 | [diff] [blame] | 655 | void mremap_userfaultfd_prep(struct vm_area_struct *vma, |
| 656 | struct vm_userfaultfd_ctx *vm_ctx) |
| 657 | { |
| 658 | struct userfaultfd_ctx *ctx; |
| 659 | |
| 660 | ctx = vma->vm_userfaultfd_ctx.ctx; |
| 661 | if (ctx && (ctx->features & UFFD_FEATURE_EVENT_REMAP)) { |
| 662 | vm_ctx->ctx = ctx; |
| 663 | userfaultfd_ctx_get(ctx); |
| 664 | } |
| 665 | } |
| 666 | |
Andrea Arcangeli | 90794bf | 2017-02-22 15:42:37 -0800 | [diff] [blame] | 667 | void mremap_userfaultfd_complete(struct vm_userfaultfd_ctx *vm_ctx, |
Pavel Emelyanov | 72f8765 | 2017-02-22 15:42:34 -0800 | [diff] [blame] | 668 | unsigned long from, unsigned long to, |
| 669 | unsigned long len) |
| 670 | { |
Andrea Arcangeli | 90794bf | 2017-02-22 15:42:37 -0800 | [diff] [blame] | 671 | struct userfaultfd_ctx *ctx = vm_ctx->ctx; |
Pavel Emelyanov | 72f8765 | 2017-02-22 15:42:34 -0800 | [diff] [blame] | 672 | struct userfaultfd_wait_queue ewq; |
| 673 | |
| 674 | if (!ctx) |
| 675 | return; |
| 676 | |
| 677 | if (to & ~PAGE_MASK) { |
| 678 | userfaultfd_ctx_put(ctx); |
| 679 | return; |
| 680 | } |
| 681 | |
| 682 | msg_init(&ewq.msg); |
| 683 | |
| 684 | ewq.msg.event = UFFD_EVENT_REMAP; |
| 685 | ewq.msg.arg.remap.from = from; |
| 686 | ewq.msg.arg.remap.to = to; |
| 687 | ewq.msg.arg.remap.len = len; |
| 688 | |
| 689 | userfaultfd_event_wait_completion(ctx, &ewq); |
| 690 | } |
| 691 | |
Mike Rapoport | d811914 | 2017-02-24 14:56:02 -0800 | [diff] [blame] | 692 | void userfaultfd_remove(struct vm_area_struct *vma, |
| 693 | struct vm_area_struct **prev, |
| 694 | unsigned long start, unsigned long end) |
Pavel Emelyanov | 05ce772 | 2017-02-22 15:42:40 -0800 | [diff] [blame] | 695 | { |
| 696 | struct mm_struct *mm = vma->vm_mm; |
| 697 | struct userfaultfd_ctx *ctx; |
| 698 | struct userfaultfd_wait_queue ewq; |
| 699 | |
| 700 | ctx = vma->vm_userfaultfd_ctx.ctx; |
Mike Rapoport | d811914 | 2017-02-24 14:56:02 -0800 | [diff] [blame] | 701 | if (!ctx || !(ctx->features & UFFD_FEATURE_EVENT_REMOVE)) |
Pavel Emelyanov | 05ce772 | 2017-02-22 15:42:40 -0800 | [diff] [blame] | 702 | return; |
| 703 | |
| 704 | userfaultfd_ctx_get(ctx); |
| 705 | up_read(&mm->mmap_sem); |
| 706 | |
| 707 | *prev = NULL; /* We wait for ACK w/o the mmap semaphore */ |
| 708 | |
| 709 | msg_init(&ewq.msg); |
| 710 | |
Mike Rapoport | d811914 | 2017-02-24 14:56:02 -0800 | [diff] [blame] | 711 | ewq.msg.event = UFFD_EVENT_REMOVE; |
| 712 | ewq.msg.arg.remove.start = start; |
| 713 | ewq.msg.arg.remove.end = end; |
Pavel Emelyanov | 05ce772 | 2017-02-22 15:42:40 -0800 | [diff] [blame] | 714 | |
| 715 | userfaultfd_event_wait_completion(ctx, &ewq); |
| 716 | |
| 717 | down_read(&mm->mmap_sem); |
| 718 | } |
| 719 | |
Mike Rapoport | 897ab3e | 2017-02-24 14:58:22 -0800 | [diff] [blame] | 720 | static bool has_unmap_ctx(struct userfaultfd_ctx *ctx, struct list_head *unmaps, |
| 721 | unsigned long start, unsigned long end) |
| 722 | { |
| 723 | struct userfaultfd_unmap_ctx *unmap_ctx; |
| 724 | |
| 725 | list_for_each_entry(unmap_ctx, unmaps, list) |
| 726 | if (unmap_ctx->ctx == ctx && unmap_ctx->start == start && |
| 727 | unmap_ctx->end == end) |
| 728 | return true; |
| 729 | |
| 730 | return false; |
| 731 | } |
| 732 | |
| 733 | int userfaultfd_unmap_prep(struct vm_area_struct *vma, |
| 734 | unsigned long start, unsigned long end, |
| 735 | struct list_head *unmaps) |
| 736 | { |
| 737 | for ( ; vma && vma->vm_start < end; vma = vma->vm_next) { |
| 738 | struct userfaultfd_unmap_ctx *unmap_ctx; |
| 739 | struct userfaultfd_ctx *ctx = vma->vm_userfaultfd_ctx.ctx; |
| 740 | |
| 741 | if (!ctx || !(ctx->features & UFFD_FEATURE_EVENT_UNMAP) || |
| 742 | has_unmap_ctx(ctx, unmaps, start, end)) |
| 743 | continue; |
| 744 | |
| 745 | unmap_ctx = kzalloc(sizeof(*unmap_ctx), GFP_KERNEL); |
| 746 | if (!unmap_ctx) |
| 747 | return -ENOMEM; |
| 748 | |
| 749 | userfaultfd_ctx_get(ctx); |
| 750 | unmap_ctx->ctx = ctx; |
| 751 | unmap_ctx->start = start; |
| 752 | unmap_ctx->end = end; |
| 753 | list_add_tail(&unmap_ctx->list, unmaps); |
| 754 | } |
| 755 | |
| 756 | return 0; |
| 757 | } |
| 758 | |
| 759 | void userfaultfd_unmap_complete(struct mm_struct *mm, struct list_head *uf) |
| 760 | { |
| 761 | struct userfaultfd_unmap_ctx *ctx, *n; |
| 762 | struct userfaultfd_wait_queue ewq; |
| 763 | |
| 764 | list_for_each_entry_safe(ctx, n, uf, list) { |
| 765 | msg_init(&ewq.msg); |
| 766 | |
| 767 | ewq.msg.event = UFFD_EVENT_UNMAP; |
| 768 | ewq.msg.arg.remove.start = ctx->start; |
| 769 | ewq.msg.arg.remove.end = ctx->end; |
| 770 | |
| 771 | userfaultfd_event_wait_completion(ctx->ctx, &ewq); |
| 772 | |
| 773 | list_del(&ctx->list); |
| 774 | kfree(ctx); |
| 775 | } |
| 776 | } |
| 777 | |
Mike Rapoport | ca49ca7 | 2017-02-24 14:58:25 -0800 | [diff] [blame] | 778 | void userfaultfd_exit(struct mm_struct *mm) |
| 779 | { |
| 780 | struct vm_area_struct *vma = mm->mmap; |
| 781 | |
| 782 | /* |
| 783 | * We can do the vma walk without locking because the caller |
| 784 | * (exit_mm) knows it now has exclusive access |
| 785 | */ |
| 786 | while (vma) { |
| 787 | struct userfaultfd_ctx *ctx = vma->vm_userfaultfd_ctx.ctx; |
| 788 | |
| 789 | if (ctx && (ctx->features & UFFD_FEATURE_EVENT_EXIT)) { |
| 790 | struct userfaultfd_wait_queue ewq; |
| 791 | |
| 792 | userfaultfd_ctx_get(ctx); |
| 793 | |
| 794 | msg_init(&ewq.msg); |
| 795 | ewq.msg.event = UFFD_EVENT_EXIT; |
| 796 | |
| 797 | userfaultfd_event_wait_completion(ctx, &ewq); |
| 798 | |
| 799 | ctx->features &= ~UFFD_FEATURE_EVENT_EXIT; |
| 800 | } |
| 801 | |
| 802 | vma = vma->vm_next; |
| 803 | } |
| 804 | } |
| 805 | |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 806 | static int userfaultfd_release(struct inode *inode, struct file *file) |
| 807 | { |
| 808 | struct userfaultfd_ctx *ctx = file->private_data; |
| 809 | struct mm_struct *mm = ctx->mm; |
| 810 | struct vm_area_struct *vma, *prev; |
| 811 | /* len == 0 means wake all */ |
| 812 | struct userfaultfd_wake_range range = { .len = 0, }; |
| 813 | unsigned long new_flags; |
| 814 | |
| 815 | ACCESS_ONCE(ctx->released) = true; |
| 816 | |
Oleg Nesterov | d2005e3 | 2016-05-20 16:58:36 -0700 | [diff] [blame] | 817 | if (!mmget_not_zero(mm)) |
| 818 | goto wakeup; |
| 819 | |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 820 | /* |
| 821 | * Flush page faults out of all CPUs. NOTE: all page faults |
| 822 | * must be retried without returning VM_FAULT_SIGBUS if |
| 823 | * userfaultfd_ctx_get() succeeds but vma->vma_userfault_ctx |
| 824 | * changes while handle_userfault released the mmap_sem. So |
| 825 | * it's critical that released is set to true (above), before |
| 826 | * taking the mmap_sem for writing. |
| 827 | */ |
| 828 | down_write(&mm->mmap_sem); |
| 829 | prev = NULL; |
| 830 | for (vma = mm->mmap; vma; vma = vma->vm_next) { |
| 831 | cond_resched(); |
| 832 | BUG_ON(!!vma->vm_userfaultfd_ctx.ctx ^ |
| 833 | !!(vma->vm_flags & (VM_UFFD_MISSING | VM_UFFD_WP))); |
| 834 | if (vma->vm_userfaultfd_ctx.ctx != ctx) { |
| 835 | prev = vma; |
| 836 | continue; |
| 837 | } |
| 838 | new_flags = vma->vm_flags & ~(VM_UFFD_MISSING | VM_UFFD_WP); |
| 839 | prev = vma_merge(mm, prev, vma->vm_start, vma->vm_end, |
| 840 | new_flags, vma->anon_vma, |
| 841 | vma->vm_file, vma->vm_pgoff, |
| 842 | vma_policy(vma), |
| 843 | NULL_VM_UFFD_CTX); |
| 844 | if (prev) |
| 845 | vma = prev; |
| 846 | else |
| 847 | prev = vma; |
| 848 | vma->vm_flags = new_flags; |
| 849 | vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX; |
| 850 | } |
| 851 | up_write(&mm->mmap_sem); |
Oleg Nesterov | d2005e3 | 2016-05-20 16:58:36 -0700 | [diff] [blame] | 852 | mmput(mm); |
| 853 | wakeup: |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 854 | /* |
Andrea Arcangeli | 15b726e | 2015-09-04 15:46:44 -0700 | [diff] [blame] | 855 | * After no new page faults can wait on this fault_*wqh, flush |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 856 | * the last page faults that may have been already waiting on |
Andrea Arcangeli | 15b726e | 2015-09-04 15:46:44 -0700 | [diff] [blame] | 857 | * the fault_*wqh. |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 858 | */ |
Andrea Arcangeli | 15b726e | 2015-09-04 15:46:44 -0700 | [diff] [blame] | 859 | spin_lock(&ctx->fault_pending_wqh.lock); |
Andrea Arcangeli | ac5be6b | 2015-09-22 14:58:49 -0700 | [diff] [blame] | 860 | __wake_up_locked_key(&ctx->fault_pending_wqh, TASK_NORMAL, &range); |
| 861 | __wake_up_locked_key(&ctx->fault_wqh, TASK_NORMAL, &range); |
Andrea Arcangeli | 15b726e | 2015-09-04 15:46:44 -0700 | [diff] [blame] | 862 | spin_unlock(&ctx->fault_pending_wqh.lock); |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 863 | |
| 864 | wake_up_poll(&ctx->fd_wqh, POLLHUP); |
| 865 | userfaultfd_ctx_put(ctx); |
| 866 | return 0; |
| 867 | } |
| 868 | |
Andrea Arcangeli | 15b726e | 2015-09-04 15:46:44 -0700 | [diff] [blame] | 869 | /* fault_pending_wqh.lock must be hold by the caller */ |
Pavel Emelyanov | 6dcc27f | 2017-02-22 15:42:18 -0800 | [diff] [blame] | 870 | static inline struct userfaultfd_wait_queue *find_userfault_in( |
| 871 | wait_queue_head_t *wqh) |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 872 | { |
| 873 | wait_queue_t *wq; |
Andrea Arcangeli | 15b726e | 2015-09-04 15:46:44 -0700 | [diff] [blame] | 874 | struct userfaultfd_wait_queue *uwq; |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 875 | |
Pavel Emelyanov | 6dcc27f | 2017-02-22 15:42:18 -0800 | [diff] [blame] | 876 | VM_BUG_ON(!spin_is_locked(&wqh->lock)); |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 877 | |
Andrea Arcangeli | 15b726e | 2015-09-04 15:46:44 -0700 | [diff] [blame] | 878 | uwq = NULL; |
Pavel Emelyanov | 6dcc27f | 2017-02-22 15:42:18 -0800 | [diff] [blame] | 879 | if (!waitqueue_active(wqh)) |
Andrea Arcangeli | 15b726e | 2015-09-04 15:46:44 -0700 | [diff] [blame] | 880 | goto out; |
| 881 | /* walk in reverse to provide FIFO behavior to read userfaults */ |
Pavel Emelyanov | 6dcc27f | 2017-02-22 15:42:18 -0800 | [diff] [blame] | 882 | wq = list_last_entry(&wqh->task_list, typeof(*wq), task_list); |
Andrea Arcangeli | 15b726e | 2015-09-04 15:46:44 -0700 | [diff] [blame] | 883 | uwq = container_of(wq, struct userfaultfd_wait_queue, wq); |
| 884 | out: |
| 885 | return uwq; |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 886 | } |
| 887 | |
Pavel Emelyanov | 6dcc27f | 2017-02-22 15:42:18 -0800 | [diff] [blame] | 888 | static inline struct userfaultfd_wait_queue *find_userfault( |
| 889 | struct userfaultfd_ctx *ctx) |
| 890 | { |
| 891 | return find_userfault_in(&ctx->fault_pending_wqh); |
| 892 | } |
| 893 | |
Pavel Emelyanov | 9cd75c3 | 2017-02-22 15:42:21 -0800 | [diff] [blame] | 894 | static inline struct userfaultfd_wait_queue *find_userfault_evt( |
| 895 | struct userfaultfd_ctx *ctx) |
| 896 | { |
| 897 | return find_userfault_in(&ctx->event_wqh); |
| 898 | } |
| 899 | |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 900 | static unsigned int userfaultfd_poll(struct file *file, poll_table *wait) |
| 901 | { |
| 902 | struct userfaultfd_ctx *ctx = file->private_data; |
| 903 | unsigned int ret; |
| 904 | |
| 905 | poll_wait(file, &ctx->fd_wqh, wait); |
| 906 | |
| 907 | switch (ctx->state) { |
| 908 | case UFFD_STATE_WAIT_API: |
| 909 | return POLLERR; |
| 910 | case UFFD_STATE_RUNNING: |
Andrea Arcangeli | ba85c70 | 2015-09-04 15:46:41 -0700 | [diff] [blame] | 911 | /* |
| 912 | * poll() never guarantees that read won't block. |
| 913 | * userfaults can be waken before they're read(). |
| 914 | */ |
| 915 | if (unlikely(!(file->f_flags & O_NONBLOCK))) |
| 916 | return POLLERR; |
Andrea Arcangeli | 15b726e | 2015-09-04 15:46:44 -0700 | [diff] [blame] | 917 | /* |
| 918 | * lockless access to see if there are pending faults |
| 919 | * __pollwait last action is the add_wait_queue but |
| 920 | * the spin_unlock would allow the waitqueue_active to |
| 921 | * pass above the actual list_add inside |
| 922 | * add_wait_queue critical section. So use a full |
| 923 | * memory barrier to serialize the list_add write of |
| 924 | * add_wait_queue() with the waitqueue_active read |
| 925 | * below. |
| 926 | */ |
| 927 | ret = 0; |
| 928 | smp_mb(); |
| 929 | if (waitqueue_active(&ctx->fault_pending_wqh)) |
| 930 | ret = POLLIN; |
Pavel Emelyanov | 9cd75c3 | 2017-02-22 15:42:21 -0800 | [diff] [blame] | 931 | else if (waitqueue_active(&ctx->event_wqh)) |
| 932 | ret = POLLIN; |
| 933 | |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 934 | return ret; |
| 935 | default: |
Andrea Arcangeli | 8474901 | 2017-02-22 15:42:12 -0800 | [diff] [blame] | 936 | WARN_ON_ONCE(1); |
| 937 | return POLLERR; |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 938 | } |
| 939 | } |
| 940 | |
Pavel Emelyanov | 893e26e | 2017-02-22 15:42:27 -0800 | [diff] [blame] | 941 | static const struct file_operations userfaultfd_fops; |
| 942 | |
| 943 | static int resolve_userfault_fork(struct userfaultfd_ctx *ctx, |
| 944 | struct userfaultfd_ctx *new, |
| 945 | struct uffd_msg *msg) |
| 946 | { |
| 947 | int fd; |
| 948 | struct file *file; |
| 949 | unsigned int flags = new->flags & UFFD_SHARED_FCNTL_FLAGS; |
| 950 | |
| 951 | fd = get_unused_fd_flags(flags); |
| 952 | if (fd < 0) |
| 953 | return fd; |
| 954 | |
| 955 | file = anon_inode_getfile("[userfaultfd]", &userfaultfd_fops, new, |
| 956 | O_RDWR | flags); |
| 957 | if (IS_ERR(file)) { |
| 958 | put_unused_fd(fd); |
| 959 | return PTR_ERR(file); |
| 960 | } |
| 961 | |
| 962 | fd_install(fd, file); |
| 963 | msg->arg.reserved.reserved1 = 0; |
| 964 | msg->arg.fork.ufd = fd; |
| 965 | |
| 966 | return 0; |
| 967 | } |
| 968 | |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 969 | static ssize_t userfaultfd_ctx_read(struct userfaultfd_ctx *ctx, int no_wait, |
Andrea Arcangeli | a9b85f9 | 2015-09-04 15:46:37 -0700 | [diff] [blame] | 970 | struct uffd_msg *msg) |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 971 | { |
| 972 | ssize_t ret; |
| 973 | DECLARE_WAITQUEUE(wait, current); |
Andrea Arcangeli | 15b726e | 2015-09-04 15:46:44 -0700 | [diff] [blame] | 974 | struct userfaultfd_wait_queue *uwq; |
Pavel Emelyanov | 893e26e | 2017-02-22 15:42:27 -0800 | [diff] [blame] | 975 | /* |
| 976 | * Handling fork event requires sleeping operations, so |
| 977 | * we drop the event_wqh lock, then do these ops, then |
| 978 | * lock it back and wake up the waiter. While the lock is |
| 979 | * dropped the ewq may go away so we keep track of it |
| 980 | * carefully. |
| 981 | */ |
| 982 | LIST_HEAD(fork_event); |
| 983 | struct userfaultfd_ctx *fork_nctx = NULL; |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 984 | |
Andrea Arcangeli | 15b726e | 2015-09-04 15:46:44 -0700 | [diff] [blame] | 985 | /* always take the fd_wqh lock before the fault_pending_wqh lock */ |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 986 | spin_lock(&ctx->fd_wqh.lock); |
| 987 | __add_wait_queue(&ctx->fd_wqh, &wait); |
| 988 | for (;;) { |
| 989 | set_current_state(TASK_INTERRUPTIBLE); |
Andrea Arcangeli | 15b726e | 2015-09-04 15:46:44 -0700 | [diff] [blame] | 990 | spin_lock(&ctx->fault_pending_wqh.lock); |
| 991 | uwq = find_userfault(ctx); |
| 992 | if (uwq) { |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 993 | /* |
Andrea Arcangeli | 2c5b7e1 | 2015-09-04 15:47:23 -0700 | [diff] [blame] | 994 | * Use a seqcount to repeat the lockless check |
| 995 | * in wake_userfault() to avoid missing |
| 996 | * wakeups because during the refile both |
| 997 | * waitqueue could become empty if this is the |
| 998 | * only userfault. |
| 999 | */ |
| 1000 | write_seqcount_begin(&ctx->refile_seq); |
| 1001 | |
| 1002 | /* |
Andrea Arcangeli | 15b726e | 2015-09-04 15:46:44 -0700 | [diff] [blame] | 1003 | * The fault_pending_wqh.lock prevents the uwq |
| 1004 | * to disappear from under us. |
| 1005 | * |
| 1006 | * Refile this userfault from |
| 1007 | * fault_pending_wqh to fault_wqh, it's not |
| 1008 | * pending anymore after we read it. |
| 1009 | * |
| 1010 | * Use list_del() by hand (as |
| 1011 | * userfaultfd_wake_function also uses |
| 1012 | * list_del_init() by hand) to be sure nobody |
| 1013 | * changes __remove_wait_queue() to use |
| 1014 | * list_del_init() in turn breaking the |
| 1015 | * !list_empty_careful() check in |
| 1016 | * handle_userfault(). The uwq->wq.task_list |
| 1017 | * must never be empty at any time during the |
| 1018 | * refile, or the waitqueue could disappear |
| 1019 | * from under us. The "wait_queue_head_t" |
| 1020 | * parameter of __remove_wait_queue() is unused |
| 1021 | * anyway. |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 1022 | */ |
Andrea Arcangeli | 15b726e | 2015-09-04 15:46:44 -0700 | [diff] [blame] | 1023 | list_del(&uwq->wq.task_list); |
| 1024 | __add_wait_queue(&ctx->fault_wqh, &uwq->wq); |
| 1025 | |
Andrea Arcangeli | 2c5b7e1 | 2015-09-04 15:47:23 -0700 | [diff] [blame] | 1026 | write_seqcount_end(&ctx->refile_seq); |
| 1027 | |
Andrea Arcangeli | a9b85f9 | 2015-09-04 15:46:37 -0700 | [diff] [blame] | 1028 | /* careful to always initialize msg if ret == 0 */ |
| 1029 | *msg = uwq->msg; |
Andrea Arcangeli | 15b726e | 2015-09-04 15:46:44 -0700 | [diff] [blame] | 1030 | spin_unlock(&ctx->fault_pending_wqh.lock); |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 1031 | ret = 0; |
| 1032 | break; |
| 1033 | } |
Andrea Arcangeli | 15b726e | 2015-09-04 15:46:44 -0700 | [diff] [blame] | 1034 | spin_unlock(&ctx->fault_pending_wqh.lock); |
Pavel Emelyanov | 9cd75c3 | 2017-02-22 15:42:21 -0800 | [diff] [blame] | 1035 | |
| 1036 | spin_lock(&ctx->event_wqh.lock); |
| 1037 | uwq = find_userfault_evt(ctx); |
| 1038 | if (uwq) { |
| 1039 | *msg = uwq->msg; |
| 1040 | |
Pavel Emelyanov | 893e26e | 2017-02-22 15:42:27 -0800 | [diff] [blame] | 1041 | if (uwq->msg.event == UFFD_EVENT_FORK) { |
| 1042 | fork_nctx = (struct userfaultfd_ctx *) |
| 1043 | (unsigned long) |
| 1044 | uwq->msg.arg.reserved.reserved1; |
| 1045 | list_move(&uwq->wq.task_list, &fork_event); |
| 1046 | spin_unlock(&ctx->event_wqh.lock); |
| 1047 | ret = 0; |
| 1048 | break; |
| 1049 | } |
| 1050 | |
Pavel Emelyanov | 9cd75c3 | 2017-02-22 15:42:21 -0800 | [diff] [blame] | 1051 | userfaultfd_event_complete(ctx, uwq); |
| 1052 | spin_unlock(&ctx->event_wqh.lock); |
| 1053 | ret = 0; |
| 1054 | break; |
| 1055 | } |
| 1056 | spin_unlock(&ctx->event_wqh.lock); |
| 1057 | |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 1058 | if (signal_pending(current)) { |
| 1059 | ret = -ERESTARTSYS; |
| 1060 | break; |
| 1061 | } |
| 1062 | if (no_wait) { |
| 1063 | ret = -EAGAIN; |
| 1064 | break; |
| 1065 | } |
| 1066 | spin_unlock(&ctx->fd_wqh.lock); |
| 1067 | schedule(); |
| 1068 | spin_lock(&ctx->fd_wqh.lock); |
| 1069 | } |
| 1070 | __remove_wait_queue(&ctx->fd_wqh, &wait); |
| 1071 | __set_current_state(TASK_RUNNING); |
| 1072 | spin_unlock(&ctx->fd_wqh.lock); |
| 1073 | |
Pavel Emelyanov | 893e26e | 2017-02-22 15:42:27 -0800 | [diff] [blame] | 1074 | if (!ret && msg->event == UFFD_EVENT_FORK) { |
| 1075 | ret = resolve_userfault_fork(ctx, fork_nctx, msg); |
| 1076 | |
| 1077 | if (!ret) { |
| 1078 | spin_lock(&ctx->event_wqh.lock); |
| 1079 | if (!list_empty(&fork_event)) { |
| 1080 | uwq = list_first_entry(&fork_event, |
| 1081 | typeof(*uwq), |
| 1082 | wq.task_list); |
| 1083 | list_del(&uwq->wq.task_list); |
| 1084 | __add_wait_queue(&ctx->event_wqh, &uwq->wq); |
| 1085 | userfaultfd_event_complete(ctx, uwq); |
| 1086 | } |
| 1087 | spin_unlock(&ctx->event_wqh.lock); |
| 1088 | } |
| 1089 | } |
| 1090 | |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 1091 | return ret; |
| 1092 | } |
| 1093 | |
| 1094 | static ssize_t userfaultfd_read(struct file *file, char __user *buf, |
| 1095 | size_t count, loff_t *ppos) |
| 1096 | { |
| 1097 | struct userfaultfd_ctx *ctx = file->private_data; |
| 1098 | ssize_t _ret, ret = 0; |
Andrea Arcangeli | a9b85f9 | 2015-09-04 15:46:37 -0700 | [diff] [blame] | 1099 | struct uffd_msg msg; |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 1100 | int no_wait = file->f_flags & O_NONBLOCK; |
| 1101 | |
| 1102 | if (ctx->state == UFFD_STATE_WAIT_API) |
| 1103 | return -EINVAL; |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 1104 | |
| 1105 | for (;;) { |
Andrea Arcangeli | a9b85f9 | 2015-09-04 15:46:37 -0700 | [diff] [blame] | 1106 | if (count < sizeof(msg)) |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 1107 | return ret ? ret : -EINVAL; |
Andrea Arcangeli | a9b85f9 | 2015-09-04 15:46:37 -0700 | [diff] [blame] | 1108 | _ret = userfaultfd_ctx_read(ctx, no_wait, &msg); |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 1109 | if (_ret < 0) |
| 1110 | return ret ? ret : _ret; |
Andrea Arcangeli | a9b85f9 | 2015-09-04 15:46:37 -0700 | [diff] [blame] | 1111 | if (copy_to_user((__u64 __user *) buf, &msg, sizeof(msg))) |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 1112 | return ret ? ret : -EFAULT; |
Andrea Arcangeli | a9b85f9 | 2015-09-04 15:46:37 -0700 | [diff] [blame] | 1113 | ret += sizeof(msg); |
| 1114 | buf += sizeof(msg); |
| 1115 | count -= sizeof(msg); |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 1116 | /* |
| 1117 | * Allow to read more than one fault at time but only |
| 1118 | * block if waiting for the very first one. |
| 1119 | */ |
| 1120 | no_wait = O_NONBLOCK; |
| 1121 | } |
| 1122 | } |
| 1123 | |
| 1124 | static void __wake_userfault(struct userfaultfd_ctx *ctx, |
| 1125 | struct userfaultfd_wake_range *range) |
| 1126 | { |
| 1127 | unsigned long start, end; |
| 1128 | |
| 1129 | start = range->start; |
| 1130 | end = range->start + range->len; |
| 1131 | |
Andrea Arcangeli | 15b726e | 2015-09-04 15:46:44 -0700 | [diff] [blame] | 1132 | spin_lock(&ctx->fault_pending_wqh.lock); |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 1133 | /* wake all in the range and autoremove */ |
Andrea Arcangeli | 15b726e | 2015-09-04 15:46:44 -0700 | [diff] [blame] | 1134 | if (waitqueue_active(&ctx->fault_pending_wqh)) |
Andrea Arcangeli | ac5be6b | 2015-09-22 14:58:49 -0700 | [diff] [blame] | 1135 | __wake_up_locked_key(&ctx->fault_pending_wqh, TASK_NORMAL, |
Andrea Arcangeli | 15b726e | 2015-09-04 15:46:44 -0700 | [diff] [blame] | 1136 | range); |
| 1137 | if (waitqueue_active(&ctx->fault_wqh)) |
Andrea Arcangeli | ac5be6b | 2015-09-22 14:58:49 -0700 | [diff] [blame] | 1138 | __wake_up_locked_key(&ctx->fault_wqh, TASK_NORMAL, range); |
Andrea Arcangeli | 15b726e | 2015-09-04 15:46:44 -0700 | [diff] [blame] | 1139 | spin_unlock(&ctx->fault_pending_wqh.lock); |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 1140 | } |
| 1141 | |
| 1142 | static __always_inline void wake_userfault(struct userfaultfd_ctx *ctx, |
| 1143 | struct userfaultfd_wake_range *range) |
| 1144 | { |
Andrea Arcangeli | 2c5b7e1 | 2015-09-04 15:47:23 -0700 | [diff] [blame] | 1145 | unsigned seq; |
| 1146 | bool need_wakeup; |
| 1147 | |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 1148 | /* |
| 1149 | * To be sure waitqueue_active() is not reordered by the CPU |
| 1150 | * before the pagetable update, use an explicit SMP memory |
| 1151 | * barrier here. PT lock release or up_read(mmap_sem) still |
| 1152 | * have release semantics that can allow the |
| 1153 | * waitqueue_active() to be reordered before the pte update. |
| 1154 | */ |
| 1155 | smp_mb(); |
| 1156 | |
| 1157 | /* |
| 1158 | * Use waitqueue_active because it's very frequent to |
| 1159 | * change the address space atomically even if there are no |
| 1160 | * userfaults yet. So we take the spinlock only when we're |
| 1161 | * sure we've userfaults to wake. |
| 1162 | */ |
Andrea Arcangeli | 2c5b7e1 | 2015-09-04 15:47:23 -0700 | [diff] [blame] | 1163 | do { |
| 1164 | seq = read_seqcount_begin(&ctx->refile_seq); |
| 1165 | need_wakeup = waitqueue_active(&ctx->fault_pending_wqh) || |
| 1166 | waitqueue_active(&ctx->fault_wqh); |
| 1167 | cond_resched(); |
| 1168 | } while (read_seqcount_retry(&ctx->refile_seq, seq)); |
| 1169 | if (need_wakeup) |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 1170 | __wake_userfault(ctx, range); |
| 1171 | } |
| 1172 | |
| 1173 | static __always_inline int validate_range(struct mm_struct *mm, |
| 1174 | __u64 start, __u64 len) |
| 1175 | { |
| 1176 | __u64 task_size = mm->task_size; |
| 1177 | |
| 1178 | if (start & ~PAGE_MASK) |
| 1179 | return -EINVAL; |
| 1180 | if (len & ~PAGE_MASK) |
| 1181 | return -EINVAL; |
| 1182 | if (!len) |
| 1183 | return -EINVAL; |
| 1184 | if (start < mmap_min_addr) |
| 1185 | return -EINVAL; |
| 1186 | if (start >= task_size) |
| 1187 | return -EINVAL; |
| 1188 | if (len > task_size - start) |
| 1189 | return -EINVAL; |
| 1190 | return 0; |
| 1191 | } |
| 1192 | |
Mike Rapoport | ba6907d | 2017-02-22 15:43:22 -0800 | [diff] [blame] | 1193 | static inline bool vma_can_userfault(struct vm_area_struct *vma) |
| 1194 | { |
Mike Rapoport | cac6732 | 2017-02-22 15:43:40 -0800 | [diff] [blame] | 1195 | return vma_is_anonymous(vma) || is_vm_hugetlb_page(vma) || |
| 1196 | vma_is_shmem(vma); |
Mike Rapoport | ba6907d | 2017-02-22 15:43:22 -0800 | [diff] [blame] | 1197 | } |
| 1198 | |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 1199 | static int userfaultfd_register(struct userfaultfd_ctx *ctx, |
| 1200 | unsigned long arg) |
| 1201 | { |
| 1202 | struct mm_struct *mm = ctx->mm; |
| 1203 | struct vm_area_struct *vma, *prev, *cur; |
| 1204 | int ret; |
| 1205 | struct uffdio_register uffdio_register; |
| 1206 | struct uffdio_register __user *user_uffdio_register; |
| 1207 | unsigned long vm_flags, new_flags; |
| 1208 | bool found; |
Mike Rapoport | cac6732 | 2017-02-22 15:43:40 -0800 | [diff] [blame] | 1209 | bool non_anon_pages; |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 1210 | unsigned long start, end, vma_end; |
| 1211 | |
| 1212 | user_uffdio_register = (struct uffdio_register __user *) arg; |
| 1213 | |
| 1214 | ret = -EFAULT; |
| 1215 | if (copy_from_user(&uffdio_register, user_uffdio_register, |
| 1216 | sizeof(uffdio_register)-sizeof(__u64))) |
| 1217 | goto out; |
| 1218 | |
| 1219 | ret = -EINVAL; |
| 1220 | if (!uffdio_register.mode) |
| 1221 | goto out; |
| 1222 | if (uffdio_register.mode & ~(UFFDIO_REGISTER_MODE_MISSING| |
| 1223 | UFFDIO_REGISTER_MODE_WP)) |
| 1224 | goto out; |
| 1225 | vm_flags = 0; |
| 1226 | if (uffdio_register.mode & UFFDIO_REGISTER_MODE_MISSING) |
| 1227 | vm_flags |= VM_UFFD_MISSING; |
| 1228 | if (uffdio_register.mode & UFFDIO_REGISTER_MODE_WP) { |
| 1229 | vm_flags |= VM_UFFD_WP; |
| 1230 | /* |
| 1231 | * FIXME: remove the below error constraint by |
| 1232 | * implementing the wprotect tracking mode. |
| 1233 | */ |
| 1234 | ret = -EINVAL; |
| 1235 | goto out; |
| 1236 | } |
| 1237 | |
| 1238 | ret = validate_range(mm, uffdio_register.range.start, |
| 1239 | uffdio_register.range.len); |
| 1240 | if (ret) |
| 1241 | goto out; |
| 1242 | |
| 1243 | start = uffdio_register.range.start; |
| 1244 | end = start + uffdio_register.range.len; |
| 1245 | |
Oleg Nesterov | d2005e3 | 2016-05-20 16:58:36 -0700 | [diff] [blame] | 1246 | ret = -ENOMEM; |
| 1247 | if (!mmget_not_zero(mm)) |
| 1248 | goto out; |
| 1249 | |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 1250 | down_write(&mm->mmap_sem); |
| 1251 | vma = find_vma_prev(mm, start, &prev); |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 1252 | if (!vma) |
| 1253 | goto out_unlock; |
| 1254 | |
| 1255 | /* check that there's at least one vma in the range */ |
| 1256 | ret = -EINVAL; |
| 1257 | if (vma->vm_start >= end) |
| 1258 | goto out_unlock; |
| 1259 | |
| 1260 | /* |
Mike Kravetz | cab350a | 2017-02-22 15:43:04 -0800 | [diff] [blame] | 1261 | * If the first vma contains huge pages, make sure start address |
| 1262 | * is aligned to huge page size. |
| 1263 | */ |
| 1264 | if (is_vm_hugetlb_page(vma)) { |
| 1265 | unsigned long vma_hpagesize = vma_kernel_pagesize(vma); |
| 1266 | |
| 1267 | if (start & (vma_hpagesize - 1)) |
| 1268 | goto out_unlock; |
| 1269 | } |
| 1270 | |
| 1271 | /* |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 1272 | * Search for not compatible vmas. |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 1273 | */ |
| 1274 | found = false; |
Mike Rapoport | cac6732 | 2017-02-22 15:43:40 -0800 | [diff] [blame] | 1275 | non_anon_pages = false; |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 1276 | for (cur = vma; cur && cur->vm_start < end; cur = cur->vm_next) { |
| 1277 | cond_resched(); |
| 1278 | |
| 1279 | BUG_ON(!!cur->vm_userfaultfd_ctx.ctx ^ |
| 1280 | !!(cur->vm_flags & (VM_UFFD_MISSING | VM_UFFD_WP))); |
| 1281 | |
| 1282 | /* check not compatible vmas */ |
| 1283 | ret = -EINVAL; |
Mike Rapoport | ba6907d | 2017-02-22 15:43:22 -0800 | [diff] [blame] | 1284 | if (!vma_can_userfault(cur)) |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 1285 | goto out_unlock; |
Mike Kravetz | cab350a | 2017-02-22 15:43:04 -0800 | [diff] [blame] | 1286 | /* |
| 1287 | * If this vma contains ending address, and huge pages |
| 1288 | * check alignment. |
| 1289 | */ |
| 1290 | if (is_vm_hugetlb_page(cur) && end <= cur->vm_end && |
| 1291 | end > cur->vm_start) { |
| 1292 | unsigned long vma_hpagesize = vma_kernel_pagesize(cur); |
| 1293 | |
| 1294 | ret = -EINVAL; |
| 1295 | |
| 1296 | if (end & (vma_hpagesize - 1)) |
| 1297 | goto out_unlock; |
| 1298 | } |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 1299 | |
| 1300 | /* |
| 1301 | * Check that this vma isn't already owned by a |
| 1302 | * different userfaultfd. We can't allow more than one |
| 1303 | * userfaultfd to own a single vma simultaneously or we |
| 1304 | * wouldn't know which one to deliver the userfaults to. |
| 1305 | */ |
| 1306 | ret = -EBUSY; |
| 1307 | if (cur->vm_userfaultfd_ctx.ctx && |
| 1308 | cur->vm_userfaultfd_ctx.ctx != ctx) |
| 1309 | goto out_unlock; |
| 1310 | |
Mike Kravetz | cab350a | 2017-02-22 15:43:04 -0800 | [diff] [blame] | 1311 | /* |
| 1312 | * Note vmas containing huge pages |
| 1313 | */ |
Mike Rapoport | cac6732 | 2017-02-22 15:43:40 -0800 | [diff] [blame] | 1314 | if (is_vm_hugetlb_page(cur) || vma_is_shmem(cur)) |
| 1315 | non_anon_pages = true; |
Mike Kravetz | cab350a | 2017-02-22 15:43:04 -0800 | [diff] [blame] | 1316 | |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 1317 | found = true; |
| 1318 | } |
| 1319 | BUG_ON(!found); |
| 1320 | |
| 1321 | if (vma->vm_start < start) |
| 1322 | prev = vma; |
| 1323 | |
| 1324 | ret = 0; |
| 1325 | do { |
| 1326 | cond_resched(); |
| 1327 | |
Mike Rapoport | ba6907d | 2017-02-22 15:43:22 -0800 | [diff] [blame] | 1328 | BUG_ON(!vma_can_userfault(vma)); |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 1329 | BUG_ON(vma->vm_userfaultfd_ctx.ctx && |
| 1330 | vma->vm_userfaultfd_ctx.ctx != ctx); |
| 1331 | |
| 1332 | /* |
| 1333 | * Nothing to do: this vma is already registered into this |
| 1334 | * userfaultfd and with the right tracking mode too. |
| 1335 | */ |
| 1336 | if (vma->vm_userfaultfd_ctx.ctx == ctx && |
| 1337 | (vma->vm_flags & vm_flags) == vm_flags) |
| 1338 | goto skip; |
| 1339 | |
| 1340 | if (vma->vm_start > start) |
| 1341 | start = vma->vm_start; |
| 1342 | vma_end = min(end, vma->vm_end); |
| 1343 | |
| 1344 | new_flags = (vma->vm_flags & ~vm_flags) | vm_flags; |
| 1345 | prev = vma_merge(mm, prev, start, vma_end, new_flags, |
| 1346 | vma->anon_vma, vma->vm_file, vma->vm_pgoff, |
| 1347 | vma_policy(vma), |
| 1348 | ((struct vm_userfaultfd_ctx){ ctx })); |
| 1349 | if (prev) { |
| 1350 | vma = prev; |
| 1351 | goto next; |
| 1352 | } |
| 1353 | if (vma->vm_start < start) { |
| 1354 | ret = split_vma(mm, vma, start, 1); |
| 1355 | if (ret) |
| 1356 | break; |
| 1357 | } |
| 1358 | if (vma->vm_end > end) { |
| 1359 | ret = split_vma(mm, vma, end, 0); |
| 1360 | if (ret) |
| 1361 | break; |
| 1362 | } |
| 1363 | next: |
| 1364 | /* |
| 1365 | * In the vma_merge() successful mprotect-like case 8: |
| 1366 | * the next vma was merged into the current one and |
| 1367 | * the current one has not been updated yet. |
| 1368 | */ |
| 1369 | vma->vm_flags = new_flags; |
| 1370 | vma->vm_userfaultfd_ctx.ctx = ctx; |
| 1371 | |
| 1372 | skip: |
| 1373 | prev = vma; |
| 1374 | start = vma->vm_end; |
| 1375 | vma = vma->vm_next; |
| 1376 | } while (vma && vma->vm_start < end); |
| 1377 | out_unlock: |
| 1378 | up_write(&mm->mmap_sem); |
Oleg Nesterov | d2005e3 | 2016-05-20 16:58:36 -0700 | [diff] [blame] | 1379 | mmput(mm); |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 1380 | if (!ret) { |
| 1381 | /* |
| 1382 | * Now that we scanned all vmas we can already tell |
| 1383 | * userland which ioctls methods are guaranteed to |
| 1384 | * succeed on this range. |
| 1385 | */ |
Mike Rapoport | cac6732 | 2017-02-22 15:43:40 -0800 | [diff] [blame] | 1386 | if (put_user(non_anon_pages ? UFFD_API_RANGE_IOCTLS_BASIC : |
Mike Kravetz | cab350a | 2017-02-22 15:43:04 -0800 | [diff] [blame] | 1387 | UFFD_API_RANGE_IOCTLS, |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 1388 | &user_uffdio_register->ioctls)) |
| 1389 | ret = -EFAULT; |
| 1390 | } |
| 1391 | out: |
| 1392 | return ret; |
| 1393 | } |
| 1394 | |
| 1395 | static int userfaultfd_unregister(struct userfaultfd_ctx *ctx, |
| 1396 | unsigned long arg) |
| 1397 | { |
| 1398 | struct mm_struct *mm = ctx->mm; |
| 1399 | struct vm_area_struct *vma, *prev, *cur; |
| 1400 | int ret; |
| 1401 | struct uffdio_range uffdio_unregister; |
| 1402 | unsigned long new_flags; |
| 1403 | bool found; |
| 1404 | unsigned long start, end, vma_end; |
| 1405 | const void __user *buf = (void __user *)arg; |
| 1406 | |
| 1407 | ret = -EFAULT; |
| 1408 | if (copy_from_user(&uffdio_unregister, buf, sizeof(uffdio_unregister))) |
| 1409 | goto out; |
| 1410 | |
| 1411 | ret = validate_range(mm, uffdio_unregister.start, |
| 1412 | uffdio_unregister.len); |
| 1413 | if (ret) |
| 1414 | goto out; |
| 1415 | |
| 1416 | start = uffdio_unregister.start; |
| 1417 | end = start + uffdio_unregister.len; |
| 1418 | |
Oleg Nesterov | d2005e3 | 2016-05-20 16:58:36 -0700 | [diff] [blame] | 1419 | ret = -ENOMEM; |
| 1420 | if (!mmget_not_zero(mm)) |
| 1421 | goto out; |
| 1422 | |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 1423 | down_write(&mm->mmap_sem); |
| 1424 | vma = find_vma_prev(mm, start, &prev); |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 1425 | if (!vma) |
| 1426 | goto out_unlock; |
| 1427 | |
| 1428 | /* check that there's at least one vma in the range */ |
| 1429 | ret = -EINVAL; |
| 1430 | if (vma->vm_start >= end) |
| 1431 | goto out_unlock; |
| 1432 | |
| 1433 | /* |
Mike Kravetz | cab350a | 2017-02-22 15:43:04 -0800 | [diff] [blame] | 1434 | * If the first vma contains huge pages, make sure start address |
| 1435 | * is aligned to huge page size. |
| 1436 | */ |
| 1437 | if (is_vm_hugetlb_page(vma)) { |
| 1438 | unsigned long vma_hpagesize = vma_kernel_pagesize(vma); |
| 1439 | |
| 1440 | if (start & (vma_hpagesize - 1)) |
| 1441 | goto out_unlock; |
| 1442 | } |
| 1443 | |
| 1444 | /* |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 1445 | * Search for not compatible vmas. |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 1446 | */ |
| 1447 | found = false; |
| 1448 | ret = -EINVAL; |
| 1449 | for (cur = vma; cur && cur->vm_start < end; cur = cur->vm_next) { |
| 1450 | cond_resched(); |
| 1451 | |
| 1452 | BUG_ON(!!cur->vm_userfaultfd_ctx.ctx ^ |
| 1453 | !!(cur->vm_flags & (VM_UFFD_MISSING | VM_UFFD_WP))); |
| 1454 | |
| 1455 | /* |
| 1456 | * Check not compatible vmas, not strictly required |
| 1457 | * here as not compatible vmas cannot have an |
| 1458 | * userfaultfd_ctx registered on them, but this |
| 1459 | * provides for more strict behavior to notice |
| 1460 | * unregistration errors. |
| 1461 | */ |
Mike Rapoport | ba6907d | 2017-02-22 15:43:22 -0800 | [diff] [blame] | 1462 | if (!vma_can_userfault(cur)) |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 1463 | goto out_unlock; |
| 1464 | |
| 1465 | found = true; |
| 1466 | } |
| 1467 | BUG_ON(!found); |
| 1468 | |
| 1469 | if (vma->vm_start < start) |
| 1470 | prev = vma; |
| 1471 | |
| 1472 | ret = 0; |
| 1473 | do { |
| 1474 | cond_resched(); |
| 1475 | |
Mike Rapoport | ba6907d | 2017-02-22 15:43:22 -0800 | [diff] [blame] | 1476 | BUG_ON(!vma_can_userfault(vma)); |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 1477 | |
| 1478 | /* |
| 1479 | * Nothing to do: this vma is already registered into this |
| 1480 | * userfaultfd and with the right tracking mode too. |
| 1481 | */ |
| 1482 | if (!vma->vm_userfaultfd_ctx.ctx) |
| 1483 | goto skip; |
| 1484 | |
| 1485 | if (vma->vm_start > start) |
| 1486 | start = vma->vm_start; |
| 1487 | vma_end = min(end, vma->vm_end); |
| 1488 | |
Andrea Arcangeli | 09fa529 | 2017-02-22 15:42:46 -0800 | [diff] [blame] | 1489 | if (userfaultfd_missing(vma)) { |
| 1490 | /* |
| 1491 | * Wake any concurrent pending userfault while |
| 1492 | * we unregister, so they will not hang |
| 1493 | * permanently and it avoids userland to call |
| 1494 | * UFFDIO_WAKE explicitly. |
| 1495 | */ |
| 1496 | struct userfaultfd_wake_range range; |
| 1497 | range.start = start; |
| 1498 | range.len = vma_end - start; |
| 1499 | wake_userfault(vma->vm_userfaultfd_ctx.ctx, &range); |
| 1500 | } |
| 1501 | |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 1502 | new_flags = vma->vm_flags & ~(VM_UFFD_MISSING | VM_UFFD_WP); |
| 1503 | prev = vma_merge(mm, prev, start, vma_end, new_flags, |
| 1504 | vma->anon_vma, vma->vm_file, vma->vm_pgoff, |
| 1505 | vma_policy(vma), |
| 1506 | NULL_VM_UFFD_CTX); |
| 1507 | if (prev) { |
| 1508 | vma = prev; |
| 1509 | goto next; |
| 1510 | } |
| 1511 | if (vma->vm_start < start) { |
| 1512 | ret = split_vma(mm, vma, start, 1); |
| 1513 | if (ret) |
| 1514 | break; |
| 1515 | } |
| 1516 | if (vma->vm_end > end) { |
| 1517 | ret = split_vma(mm, vma, end, 0); |
| 1518 | if (ret) |
| 1519 | break; |
| 1520 | } |
| 1521 | next: |
| 1522 | /* |
| 1523 | * In the vma_merge() successful mprotect-like case 8: |
| 1524 | * the next vma was merged into the current one and |
| 1525 | * the current one has not been updated yet. |
| 1526 | */ |
| 1527 | vma->vm_flags = new_flags; |
| 1528 | vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX; |
| 1529 | |
| 1530 | skip: |
| 1531 | prev = vma; |
| 1532 | start = vma->vm_end; |
| 1533 | vma = vma->vm_next; |
| 1534 | } while (vma && vma->vm_start < end); |
| 1535 | out_unlock: |
| 1536 | up_write(&mm->mmap_sem); |
Oleg Nesterov | d2005e3 | 2016-05-20 16:58:36 -0700 | [diff] [blame] | 1537 | mmput(mm); |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 1538 | out: |
| 1539 | return ret; |
| 1540 | } |
| 1541 | |
| 1542 | /* |
Andrea Arcangeli | ba85c70 | 2015-09-04 15:46:41 -0700 | [diff] [blame] | 1543 | * userfaultfd_wake may be used in combination with the |
| 1544 | * UFFDIO_*_MODE_DONTWAKE to wakeup userfaults in batches. |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 1545 | */ |
| 1546 | static int userfaultfd_wake(struct userfaultfd_ctx *ctx, |
| 1547 | unsigned long arg) |
| 1548 | { |
| 1549 | int ret; |
| 1550 | struct uffdio_range uffdio_wake; |
| 1551 | struct userfaultfd_wake_range range; |
| 1552 | const void __user *buf = (void __user *)arg; |
| 1553 | |
| 1554 | ret = -EFAULT; |
| 1555 | if (copy_from_user(&uffdio_wake, buf, sizeof(uffdio_wake))) |
| 1556 | goto out; |
| 1557 | |
| 1558 | ret = validate_range(ctx->mm, uffdio_wake.start, uffdio_wake.len); |
| 1559 | if (ret) |
| 1560 | goto out; |
| 1561 | |
| 1562 | range.start = uffdio_wake.start; |
| 1563 | range.len = uffdio_wake.len; |
| 1564 | |
| 1565 | /* |
| 1566 | * len == 0 means wake all and we don't want to wake all here, |
| 1567 | * so check it again to be sure. |
| 1568 | */ |
| 1569 | VM_BUG_ON(!range.len); |
| 1570 | |
| 1571 | wake_userfault(ctx, &range); |
| 1572 | ret = 0; |
| 1573 | |
| 1574 | out: |
| 1575 | return ret; |
| 1576 | } |
| 1577 | |
Andrea Arcangeli | ad465ca | 2015-09-04 15:47:11 -0700 | [diff] [blame] | 1578 | static int userfaultfd_copy(struct userfaultfd_ctx *ctx, |
| 1579 | unsigned long arg) |
| 1580 | { |
| 1581 | __s64 ret; |
| 1582 | struct uffdio_copy uffdio_copy; |
| 1583 | struct uffdio_copy __user *user_uffdio_copy; |
| 1584 | struct userfaultfd_wake_range range; |
| 1585 | |
| 1586 | user_uffdio_copy = (struct uffdio_copy __user *) arg; |
| 1587 | |
| 1588 | ret = -EFAULT; |
| 1589 | if (copy_from_user(&uffdio_copy, user_uffdio_copy, |
| 1590 | /* don't copy "copy" last field */ |
| 1591 | sizeof(uffdio_copy)-sizeof(__s64))) |
| 1592 | goto out; |
| 1593 | |
| 1594 | ret = validate_range(ctx->mm, uffdio_copy.dst, uffdio_copy.len); |
| 1595 | if (ret) |
| 1596 | goto out; |
| 1597 | /* |
| 1598 | * double check for wraparound just in case. copy_from_user() |
| 1599 | * will later check uffdio_copy.src + uffdio_copy.len to fit |
| 1600 | * in the userland range. |
| 1601 | */ |
| 1602 | ret = -EINVAL; |
| 1603 | if (uffdio_copy.src + uffdio_copy.len <= uffdio_copy.src) |
| 1604 | goto out; |
| 1605 | if (uffdio_copy.mode & ~UFFDIO_COPY_MODE_DONTWAKE) |
| 1606 | goto out; |
Oleg Nesterov | d2005e3 | 2016-05-20 16:58:36 -0700 | [diff] [blame] | 1607 | if (mmget_not_zero(ctx->mm)) { |
| 1608 | ret = mcopy_atomic(ctx->mm, uffdio_copy.dst, uffdio_copy.src, |
| 1609 | uffdio_copy.len); |
| 1610 | mmput(ctx->mm); |
Mike Rapoport | 9633318 | 2017-02-24 14:58:31 -0800 | [diff] [blame] | 1611 | } else { |
| 1612 | return -ENOSPC; |
Oleg Nesterov | d2005e3 | 2016-05-20 16:58:36 -0700 | [diff] [blame] | 1613 | } |
Andrea Arcangeli | ad465ca | 2015-09-04 15:47:11 -0700 | [diff] [blame] | 1614 | if (unlikely(put_user(ret, &user_uffdio_copy->copy))) |
| 1615 | return -EFAULT; |
| 1616 | if (ret < 0) |
| 1617 | goto out; |
| 1618 | BUG_ON(!ret); |
| 1619 | /* len == 0 would wake all */ |
| 1620 | range.len = ret; |
| 1621 | if (!(uffdio_copy.mode & UFFDIO_COPY_MODE_DONTWAKE)) { |
| 1622 | range.start = uffdio_copy.dst; |
| 1623 | wake_userfault(ctx, &range); |
| 1624 | } |
| 1625 | ret = range.len == uffdio_copy.len ? 0 : -EAGAIN; |
| 1626 | out: |
| 1627 | return ret; |
| 1628 | } |
| 1629 | |
| 1630 | static int userfaultfd_zeropage(struct userfaultfd_ctx *ctx, |
| 1631 | unsigned long arg) |
| 1632 | { |
| 1633 | __s64 ret; |
| 1634 | struct uffdio_zeropage uffdio_zeropage; |
| 1635 | struct uffdio_zeropage __user *user_uffdio_zeropage; |
| 1636 | struct userfaultfd_wake_range range; |
| 1637 | |
| 1638 | user_uffdio_zeropage = (struct uffdio_zeropage __user *) arg; |
| 1639 | |
| 1640 | ret = -EFAULT; |
| 1641 | if (copy_from_user(&uffdio_zeropage, user_uffdio_zeropage, |
| 1642 | /* don't copy "zeropage" last field */ |
| 1643 | sizeof(uffdio_zeropage)-sizeof(__s64))) |
| 1644 | goto out; |
| 1645 | |
| 1646 | ret = validate_range(ctx->mm, uffdio_zeropage.range.start, |
| 1647 | uffdio_zeropage.range.len); |
| 1648 | if (ret) |
| 1649 | goto out; |
| 1650 | ret = -EINVAL; |
| 1651 | if (uffdio_zeropage.mode & ~UFFDIO_ZEROPAGE_MODE_DONTWAKE) |
| 1652 | goto out; |
| 1653 | |
Oleg Nesterov | d2005e3 | 2016-05-20 16:58:36 -0700 | [diff] [blame] | 1654 | if (mmget_not_zero(ctx->mm)) { |
| 1655 | ret = mfill_zeropage(ctx->mm, uffdio_zeropage.range.start, |
| 1656 | uffdio_zeropage.range.len); |
| 1657 | mmput(ctx->mm); |
| 1658 | } |
Andrea Arcangeli | ad465ca | 2015-09-04 15:47:11 -0700 | [diff] [blame] | 1659 | if (unlikely(put_user(ret, &user_uffdio_zeropage->zeropage))) |
| 1660 | return -EFAULT; |
| 1661 | if (ret < 0) |
| 1662 | goto out; |
| 1663 | /* len == 0 would wake all */ |
| 1664 | BUG_ON(!ret); |
| 1665 | range.len = ret; |
| 1666 | if (!(uffdio_zeropage.mode & UFFDIO_ZEROPAGE_MODE_DONTWAKE)) { |
| 1667 | range.start = uffdio_zeropage.range.start; |
| 1668 | wake_userfault(ctx, &range); |
| 1669 | } |
| 1670 | ret = range.len == uffdio_zeropage.range.len ? 0 : -EAGAIN; |
| 1671 | out: |
| 1672 | return ret; |
| 1673 | } |
| 1674 | |
Pavel Emelyanov | 9cd75c3 | 2017-02-22 15:42:21 -0800 | [diff] [blame] | 1675 | static inline unsigned int uffd_ctx_features(__u64 user_features) |
| 1676 | { |
| 1677 | /* |
| 1678 | * For the current set of features the bits just coincide |
| 1679 | */ |
| 1680 | return (unsigned int)user_features; |
| 1681 | } |
| 1682 | |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 1683 | /* |
| 1684 | * userland asks for a certain API version and we return which bits |
| 1685 | * and ioctl commands are implemented in this kernel for such API |
| 1686 | * version or -EINVAL if unknown. |
| 1687 | */ |
| 1688 | static int userfaultfd_api(struct userfaultfd_ctx *ctx, |
| 1689 | unsigned long arg) |
| 1690 | { |
| 1691 | struct uffdio_api uffdio_api; |
| 1692 | void __user *buf = (void __user *)arg; |
| 1693 | int ret; |
Andrea Arcangeli | 6560314 | 2017-02-22 15:42:24 -0800 | [diff] [blame] | 1694 | __u64 features; |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 1695 | |
| 1696 | ret = -EINVAL; |
| 1697 | if (ctx->state != UFFD_STATE_WAIT_API) |
| 1698 | goto out; |
| 1699 | ret = -EFAULT; |
Andrea Arcangeli | a9b85f9 | 2015-09-04 15:46:37 -0700 | [diff] [blame] | 1700 | if (copy_from_user(&uffdio_api, buf, sizeof(uffdio_api))) |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 1701 | goto out; |
Andrea Arcangeli | 6560314 | 2017-02-22 15:42:24 -0800 | [diff] [blame] | 1702 | features = uffdio_api.features; |
| 1703 | if (uffdio_api.api != UFFD_API || (features & ~UFFD_API_FEATURES)) { |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 1704 | memset(&uffdio_api, 0, sizeof(uffdio_api)); |
| 1705 | if (copy_to_user(buf, &uffdio_api, sizeof(uffdio_api))) |
| 1706 | goto out; |
| 1707 | ret = -EINVAL; |
| 1708 | goto out; |
| 1709 | } |
Andrea Arcangeli | 6560314 | 2017-02-22 15:42:24 -0800 | [diff] [blame] | 1710 | /* report all available features and ioctls to userland */ |
| 1711 | uffdio_api.features = UFFD_API_FEATURES; |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 1712 | uffdio_api.ioctls = UFFD_API_IOCTLS; |
| 1713 | ret = -EFAULT; |
| 1714 | if (copy_to_user(buf, &uffdio_api, sizeof(uffdio_api))) |
| 1715 | goto out; |
| 1716 | ctx->state = UFFD_STATE_RUNNING; |
Andrea Arcangeli | 6560314 | 2017-02-22 15:42:24 -0800 | [diff] [blame] | 1717 | /* only enable the requested features for this uffd context */ |
| 1718 | ctx->features = uffd_ctx_features(features); |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 1719 | ret = 0; |
| 1720 | out: |
| 1721 | return ret; |
| 1722 | } |
| 1723 | |
| 1724 | static long userfaultfd_ioctl(struct file *file, unsigned cmd, |
| 1725 | unsigned long arg) |
| 1726 | { |
| 1727 | int ret = -EINVAL; |
| 1728 | struct userfaultfd_ctx *ctx = file->private_data; |
| 1729 | |
Andrea Arcangeli | e6485a4 | 2015-09-04 15:47:15 -0700 | [diff] [blame] | 1730 | if (cmd != UFFDIO_API && ctx->state == UFFD_STATE_WAIT_API) |
| 1731 | return -EINVAL; |
| 1732 | |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 1733 | switch(cmd) { |
| 1734 | case UFFDIO_API: |
| 1735 | ret = userfaultfd_api(ctx, arg); |
| 1736 | break; |
| 1737 | case UFFDIO_REGISTER: |
| 1738 | ret = userfaultfd_register(ctx, arg); |
| 1739 | break; |
| 1740 | case UFFDIO_UNREGISTER: |
| 1741 | ret = userfaultfd_unregister(ctx, arg); |
| 1742 | break; |
| 1743 | case UFFDIO_WAKE: |
| 1744 | ret = userfaultfd_wake(ctx, arg); |
| 1745 | break; |
Andrea Arcangeli | ad465ca | 2015-09-04 15:47:11 -0700 | [diff] [blame] | 1746 | case UFFDIO_COPY: |
| 1747 | ret = userfaultfd_copy(ctx, arg); |
| 1748 | break; |
| 1749 | case UFFDIO_ZEROPAGE: |
| 1750 | ret = userfaultfd_zeropage(ctx, arg); |
| 1751 | break; |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 1752 | } |
| 1753 | return ret; |
| 1754 | } |
| 1755 | |
| 1756 | #ifdef CONFIG_PROC_FS |
| 1757 | static void userfaultfd_show_fdinfo(struct seq_file *m, struct file *f) |
| 1758 | { |
| 1759 | struct userfaultfd_ctx *ctx = f->private_data; |
| 1760 | wait_queue_t *wq; |
| 1761 | struct userfaultfd_wait_queue *uwq; |
| 1762 | unsigned long pending = 0, total = 0; |
| 1763 | |
Andrea Arcangeli | 15b726e | 2015-09-04 15:46:44 -0700 | [diff] [blame] | 1764 | spin_lock(&ctx->fault_pending_wqh.lock); |
| 1765 | list_for_each_entry(wq, &ctx->fault_pending_wqh.task_list, task_list) { |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 1766 | uwq = container_of(wq, struct userfaultfd_wait_queue, wq); |
Andrea Arcangeli | 15b726e | 2015-09-04 15:46:44 -0700 | [diff] [blame] | 1767 | pending++; |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 1768 | total++; |
| 1769 | } |
Andrea Arcangeli | 15b726e | 2015-09-04 15:46:44 -0700 | [diff] [blame] | 1770 | list_for_each_entry(wq, &ctx->fault_wqh.task_list, task_list) { |
| 1771 | uwq = container_of(wq, struct userfaultfd_wait_queue, wq); |
| 1772 | total++; |
| 1773 | } |
| 1774 | spin_unlock(&ctx->fault_pending_wqh.lock); |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 1775 | |
| 1776 | /* |
| 1777 | * If more protocols will be added, there will be all shown |
| 1778 | * separated by a space. Like this: |
| 1779 | * protocols: aa:... bb:... |
| 1780 | */ |
| 1781 | seq_printf(m, "pending:\t%lu\ntotal:\t%lu\nAPI:\t%Lx:%x:%Lx\n", |
Pavel Emelyanov | 3f602d2 | 2015-09-04 15:46:34 -0700 | [diff] [blame] | 1782 | pending, total, UFFD_API, UFFD_API_FEATURES, |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 1783 | UFFD_API_IOCTLS|UFFD_API_RANGE_IOCTLS); |
| 1784 | } |
| 1785 | #endif |
| 1786 | |
| 1787 | static const struct file_operations userfaultfd_fops = { |
| 1788 | #ifdef CONFIG_PROC_FS |
| 1789 | .show_fdinfo = userfaultfd_show_fdinfo, |
| 1790 | #endif |
| 1791 | .release = userfaultfd_release, |
| 1792 | .poll = userfaultfd_poll, |
| 1793 | .read = userfaultfd_read, |
| 1794 | .unlocked_ioctl = userfaultfd_ioctl, |
| 1795 | .compat_ioctl = userfaultfd_ioctl, |
| 1796 | .llseek = noop_llseek, |
| 1797 | }; |
| 1798 | |
Andrea Arcangeli | 3004ec9 | 2015-09-04 15:46:48 -0700 | [diff] [blame] | 1799 | static void init_once_userfaultfd_ctx(void *mem) |
| 1800 | { |
| 1801 | struct userfaultfd_ctx *ctx = (struct userfaultfd_ctx *) mem; |
| 1802 | |
| 1803 | init_waitqueue_head(&ctx->fault_pending_wqh); |
| 1804 | init_waitqueue_head(&ctx->fault_wqh); |
Pavel Emelyanov | 9cd75c3 | 2017-02-22 15:42:21 -0800 | [diff] [blame] | 1805 | init_waitqueue_head(&ctx->event_wqh); |
Andrea Arcangeli | 3004ec9 | 2015-09-04 15:46:48 -0700 | [diff] [blame] | 1806 | init_waitqueue_head(&ctx->fd_wqh); |
Andrea Arcangeli | 2c5b7e1 | 2015-09-04 15:47:23 -0700 | [diff] [blame] | 1807 | seqcount_init(&ctx->refile_seq); |
Andrea Arcangeli | 3004ec9 | 2015-09-04 15:46:48 -0700 | [diff] [blame] | 1808 | } |
| 1809 | |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 1810 | /** |
Masahiro Yamada | 9332ef9 | 2017-02-27 14:28:47 -0800 | [diff] [blame] | 1811 | * userfaultfd_file_create - Creates a userfaultfd file pointer. |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 1812 | * @flags: Flags for the userfaultfd file. |
| 1813 | * |
Masahiro Yamada | 9332ef9 | 2017-02-27 14:28:47 -0800 | [diff] [blame] | 1814 | * This function creates a userfaultfd file pointer, w/out installing |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 1815 | * it into the fd table. This is useful when the userfaultfd file is |
| 1816 | * used during the initialization of data structures that require |
| 1817 | * extra setup after the userfaultfd creation. So the userfaultfd |
| 1818 | * creation is split into the file pointer creation phase, and the |
| 1819 | * file descriptor installation phase. In this way races with |
| 1820 | * userspace closing the newly installed file descriptor can be |
Masahiro Yamada | 9332ef9 | 2017-02-27 14:28:47 -0800 | [diff] [blame] | 1821 | * avoided. Returns a userfaultfd file pointer, or a proper error |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 1822 | * pointer. |
| 1823 | */ |
| 1824 | static struct file *userfaultfd_file_create(int flags) |
| 1825 | { |
| 1826 | struct file *file; |
| 1827 | struct userfaultfd_ctx *ctx; |
| 1828 | |
| 1829 | BUG_ON(!current->mm); |
| 1830 | |
| 1831 | /* Check the UFFD_* constants for consistency. */ |
| 1832 | BUILD_BUG_ON(UFFD_CLOEXEC != O_CLOEXEC); |
| 1833 | BUILD_BUG_ON(UFFD_NONBLOCK != O_NONBLOCK); |
| 1834 | |
| 1835 | file = ERR_PTR(-EINVAL); |
| 1836 | if (flags & ~UFFD_SHARED_FCNTL_FLAGS) |
| 1837 | goto out; |
| 1838 | |
| 1839 | file = ERR_PTR(-ENOMEM); |
Andrea Arcangeli | 3004ec9 | 2015-09-04 15:46:48 -0700 | [diff] [blame] | 1840 | ctx = kmem_cache_alloc(userfaultfd_ctx_cachep, GFP_KERNEL); |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 1841 | if (!ctx) |
| 1842 | goto out; |
| 1843 | |
| 1844 | atomic_set(&ctx->refcount, 1); |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 1845 | ctx->flags = flags; |
Pavel Emelyanov | 9cd75c3 | 2017-02-22 15:42:21 -0800 | [diff] [blame] | 1846 | ctx->features = 0; |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 1847 | ctx->state = UFFD_STATE_WAIT_API; |
| 1848 | ctx->released = false; |
| 1849 | ctx->mm = current->mm; |
| 1850 | /* prevent the mm struct to be freed */ |
Vegard Nossum | f1f1007 | 2017-02-27 14:30:07 -0800 | [diff] [blame] | 1851 | mmgrab(ctx->mm); |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 1852 | |
| 1853 | file = anon_inode_getfile("[userfaultfd]", &userfaultfd_fops, ctx, |
| 1854 | O_RDWR | (flags & UFFD_SHARED_FCNTL_FLAGS)); |
Eric Biggers | c03e946 | 2015-09-17 16:01:54 -0700 | [diff] [blame] | 1855 | if (IS_ERR(file)) { |
Oleg Nesterov | d2005e3 | 2016-05-20 16:58:36 -0700 | [diff] [blame] | 1856 | mmdrop(ctx->mm); |
Andrea Arcangeli | 3004ec9 | 2015-09-04 15:46:48 -0700 | [diff] [blame] | 1857 | kmem_cache_free(userfaultfd_ctx_cachep, ctx); |
Eric Biggers | c03e946 | 2015-09-17 16:01:54 -0700 | [diff] [blame] | 1858 | } |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 1859 | out: |
| 1860 | return file; |
| 1861 | } |
| 1862 | |
| 1863 | SYSCALL_DEFINE1(userfaultfd, int, flags) |
| 1864 | { |
| 1865 | int fd, error; |
| 1866 | struct file *file; |
| 1867 | |
| 1868 | error = get_unused_fd_flags(flags & UFFD_SHARED_FCNTL_FLAGS); |
| 1869 | if (error < 0) |
| 1870 | return error; |
| 1871 | fd = error; |
| 1872 | |
| 1873 | file = userfaultfd_file_create(flags); |
| 1874 | if (IS_ERR(file)) { |
| 1875 | error = PTR_ERR(file); |
| 1876 | goto err_put_unused_fd; |
| 1877 | } |
| 1878 | fd_install(fd, file); |
| 1879 | |
| 1880 | return fd; |
| 1881 | |
| 1882 | err_put_unused_fd: |
| 1883 | put_unused_fd(fd); |
| 1884 | |
| 1885 | return error; |
| 1886 | } |
Andrea Arcangeli | 3004ec9 | 2015-09-04 15:46:48 -0700 | [diff] [blame] | 1887 | |
| 1888 | static int __init userfaultfd_init(void) |
| 1889 | { |
| 1890 | userfaultfd_ctx_cachep = kmem_cache_create("userfaultfd_ctx_cache", |
| 1891 | sizeof(struct userfaultfd_ctx), |
| 1892 | 0, |
| 1893 | SLAB_HWCACHE_ALIGN|SLAB_PANIC, |
| 1894 | init_once_userfaultfd_ctx); |
| 1895 | return 0; |
| 1896 | } |
| 1897 | __initcall(userfaultfd_init); |