blob: cadcd12a3d35f6ba5deb54df94c995b19d3d34a8 [file] [log] [blame]
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001/*
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 Emelyanov9cd75c32017-02-22 15:42:21 -080015#include <linux/list.h>
Andrea Arcangeli86039bd2015-09-04 15:46:31 -070016#include <linux/hashtable.h>
Ingo Molnar174cd4b2017-02-02 19:15:33 +010017#include <linux/sched/signal.h>
Ingo Molnar6e84f312017-02-08 18:51:29 +010018#include <linux/sched/mm.h>
Andrea Arcangeli86039bd2015-09-04 15:46:31 -070019#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 Kravetzcab350a2017-02-22 15:43:04 -080031#include <linux/hugetlb.h>
Andrea Arcangeli86039bd2015-09-04 15:46:31 -070032
Andrea Arcangeli3004ec92015-09-04 15:46:48 -070033static struct kmem_cache *userfaultfd_ctx_cachep __read_mostly;
34
Andrea Arcangeli86039bd2015-09-04 15:46:31 -070035enum userfaultfd_state {
36 UFFD_STATE_WAIT_API,
37 UFFD_STATE_RUNNING,
38};
39
Andrea Arcangeli3004ec92015-09-04 15:46:48 -070040/*
41 * Start with fault_pending_wqh and fault_wqh so they're more likely
42 * to be in the same cacheline.
43 */
Andrea Arcangeli86039bd2015-09-04 15:46:31 -070044struct userfaultfd_ctx {
Andrea Arcangeli15b726e2015-09-04 15:46:44 -070045 /* 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 Arcangeli86039bd2015-09-04 15:46:31 -070048 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 Emelyanov9cd75c32017-02-22 15:42:21 -080051 /* waitqueue head for events */
52 wait_queue_head_t event_wqh;
Andrea Arcangeli2c5b7e12015-09-04 15:47:23 -070053 /* a refile sequence protected by fault_pending_wqh lock */
54 struct seqcount refile_seq;
Andrea Arcangeli3004ec92015-09-04 15:46:48 -070055 /* pseudo fd refcounting */
56 atomic_t refcount;
Andrea Arcangeli86039bd2015-09-04 15:46:31 -070057 /* userfaultfd syscall flags */
58 unsigned int flags;
Pavel Emelyanov9cd75c32017-02-22 15:42:21 -080059 /* features requested from the userspace */
60 unsigned int features;
Andrea Arcangeli86039bd2015-09-04 15:46:31 -070061 /* 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 Emelyanov893e26e2017-02-22 15:42:27 -080069struct userfaultfd_fork_ctx {
70 struct userfaultfd_ctx *orig;
71 struct userfaultfd_ctx *new;
72 struct list_head list;
73};
74
Mike Rapoport897ab3e2017-02-24 14:58:22 -080075struct userfaultfd_unmap_ctx {
76 struct userfaultfd_ctx *ctx;
77 unsigned long start;
78 unsigned long end;
79 struct list_head list;
80};
81
Andrea Arcangeli86039bd2015-09-04 15:46:31 -070082struct userfaultfd_wait_queue {
Andrea Arcangelia9b85f92015-09-04 15:46:37 -070083 struct uffd_msg msg;
Ingo Molnarac6424b2017-06-20 12:06:13 +020084 wait_queue_entry_t wq;
Andrea Arcangeli86039bd2015-09-04 15:46:31 -070085 struct userfaultfd_ctx *ctx;
Andrea Arcangeli15a77c62017-01-24 15:17:59 -080086 bool waken;
Andrea Arcangeli86039bd2015-09-04 15:46:31 -070087};
88
89struct userfaultfd_wake_range {
90 unsigned long start;
91 unsigned long len;
92};
93
Ingo Molnarac6424b2017-06-20 12:06:13 +020094static int userfaultfd_wake_function(wait_queue_entry_t *wq, unsigned mode,
Andrea Arcangeli86039bd2015-09-04 15:46:31 -070095 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 Arcangeli86039bd2015-09-04 15:46:31 -0700104 /* len == 0 means wake all */
105 start = range->start;
106 len = range->len;
Andrea Arcangelia9b85f92015-09-04 15:46:37 -0700107 if (len && (start > uwq->msg.arg.pagefault.address ||
108 start + len <= uwq->msg.arg.pagefault.address))
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700109 goto out;
Andrea Arcangeli15a77c62017-01-24 15:17:59 -0800110 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 Arcangeli86039bd2015-09-04 15:46:31 -0700116 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 */
Ingo Molnar2055da92017-06-20 12:06:46 +0200132 list_del_init(&wq->entry);
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700133out:
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.
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700141 */
142static void userfaultfd_ctx_get(struct userfaultfd_ctx *ctx)
143{
144 if (!atomic_inc_not_zero(&ctx->refcount))
145 BUG();
146}
147
148/**
149 * userfaultfd_ctx_put - Releases a reference to the internal userfaultfd
150 * context.
151 * @ctx: [in] Pointer to userfaultfd context.
152 *
153 * The userfaultfd context reference must have been previously acquired either
154 * with userfaultfd_ctx_get() or userfaultfd_ctx_fdget().
155 */
156static void userfaultfd_ctx_put(struct userfaultfd_ctx *ctx)
157{
158 if (atomic_dec_and_test(&ctx->refcount)) {
159 VM_BUG_ON(spin_is_locked(&ctx->fault_pending_wqh.lock));
160 VM_BUG_ON(waitqueue_active(&ctx->fault_pending_wqh));
161 VM_BUG_ON(spin_is_locked(&ctx->fault_wqh.lock));
162 VM_BUG_ON(waitqueue_active(&ctx->fault_wqh));
Pavel Emelyanov9cd75c32017-02-22 15:42:21 -0800163 VM_BUG_ON(spin_is_locked(&ctx->event_wqh.lock));
164 VM_BUG_ON(waitqueue_active(&ctx->event_wqh));
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700165 VM_BUG_ON(spin_is_locked(&ctx->fd_wqh.lock));
166 VM_BUG_ON(waitqueue_active(&ctx->fd_wqh));
Oleg Nesterovd2005e32016-05-20 16:58:36 -0700167 mmdrop(ctx->mm);
Andrea Arcangeli3004ec92015-09-04 15:46:48 -0700168 kmem_cache_free(userfaultfd_ctx_cachep, ctx);
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700169 }
170}
171
Andrea Arcangelia9b85f92015-09-04 15:46:37 -0700172static inline void msg_init(struct uffd_msg *msg)
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700173{
Andrea Arcangelia9b85f92015-09-04 15:46:37 -0700174 BUILD_BUG_ON(sizeof(struct uffd_msg) != 32);
175 /*
176 * Must use memset to zero out the paddings or kernel data is
177 * leaked to userland.
178 */
179 memset(msg, 0, sizeof(struct uffd_msg));
180}
181
182static inline struct uffd_msg userfault_msg(unsigned long address,
183 unsigned int flags,
184 unsigned long reason)
185{
186 struct uffd_msg msg;
187 msg_init(&msg);
188 msg.event = UFFD_EVENT_PAGEFAULT;
189 msg.arg.pagefault.address = address;
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700190 if (flags & FAULT_FLAG_WRITE)
191 /*
Andrea Arcangelia4605a62017-02-22 15:42:09 -0800192 * If UFFD_FEATURE_PAGEFAULT_FLAG_WP was set in the
Andrea Arcangelia9b85f92015-09-04 15:46:37 -0700193 * uffdio_api.features and UFFD_PAGEFAULT_FLAG_WRITE
194 * was not set in a UFFD_EVENT_PAGEFAULT, it means it
195 * was a read fault, otherwise if set it means it's
196 * a write fault.
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700197 */
Andrea Arcangelia9b85f92015-09-04 15:46:37 -0700198 msg.arg.pagefault.flags |= UFFD_PAGEFAULT_FLAG_WRITE;
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700199 if (reason & VM_UFFD_WP)
200 /*
Andrea Arcangelia9b85f92015-09-04 15:46:37 -0700201 * If UFFD_FEATURE_PAGEFAULT_FLAG_WP was set in the
202 * uffdio_api.features and UFFD_PAGEFAULT_FLAG_WP was
203 * not set in a UFFD_EVENT_PAGEFAULT, it means it was
204 * a missing fault, otherwise if set it means it's a
205 * write protect fault.
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700206 */
Andrea Arcangelia9b85f92015-09-04 15:46:37 -0700207 msg.arg.pagefault.flags |= UFFD_PAGEFAULT_FLAG_WP;
208 return msg;
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700209}
210
Mike Kravetz369cd212017-02-22 15:43:10 -0800211#ifdef CONFIG_HUGETLB_PAGE
212/*
213 * Same functionality as userfaultfd_must_wait below with modifications for
214 * hugepmd ranges.
215 */
216static inline bool userfaultfd_huge_must_wait(struct userfaultfd_ctx *ctx,
Punit Agrawal7868a202017-07-06 15:39:42 -0700217 struct vm_area_struct *vma,
Mike Kravetz369cd212017-02-22 15:43:10 -0800218 unsigned long address,
219 unsigned long flags,
220 unsigned long reason)
221{
222 struct mm_struct *mm = ctx->mm;
223 pte_t *pte;
224 bool ret = true;
225
226 VM_BUG_ON(!rwsem_is_locked(&mm->mmap_sem));
227
Punit Agrawal7868a202017-07-06 15:39:42 -0700228 pte = huge_pte_offset(mm, address, vma_mmu_pagesize(vma));
Mike Kravetz369cd212017-02-22 15:43:10 -0800229 if (!pte)
230 goto out;
231
232 ret = false;
233
234 /*
235 * Lockless access: we're in a wait_event so it's ok if it
236 * changes under us.
237 */
238 if (huge_pte_none(*pte))
239 ret = true;
240 if (!huge_pte_write(*pte) && (reason & VM_UFFD_WP))
241 ret = true;
242out:
243 return ret;
244}
245#else
246static inline bool userfaultfd_huge_must_wait(struct userfaultfd_ctx *ctx,
Punit Agrawal7868a202017-07-06 15:39:42 -0700247 struct vm_area_struct *vma,
Mike Kravetz369cd212017-02-22 15:43:10 -0800248 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 Arcangeli86039bd2015-09-04 15:46:31 -0700256/*
Andrea Arcangeli8d2afd92015-09-04 15:46:51 -0700257 * 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 */
263static 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;
Kirill A. Shutemovc2febaf2017-03-09 17:24:07 +0300270 p4d_t *p4d;
Andrea Arcangeli8d2afd92015-09-04 15:46:51 -0700271 pud_t *pud;
272 pmd_t *pmd, _pmd;
273 pte_t *pte;
274 bool ret = true;
275
276 VM_BUG_ON(!rwsem_is_locked(&mm->mmap_sem));
277
278 pgd = pgd_offset(mm, address);
279 if (!pgd_present(*pgd))
280 goto out;
Kirill A. Shutemovc2febaf2017-03-09 17:24:07 +0300281 p4d = p4d_offset(pgd, address);
282 if (!p4d_present(*p4d))
283 goto out;
284 pud = pud_offset(p4d, address);
Andrea Arcangeli8d2afd92015-09-04 15:46:51 -0700285 if (!pud_present(*pud))
286 goto out;
287 pmd = pmd_offset(pud, address);
288 /*
289 * READ_ONCE must function as a barrier with narrower scope
290 * and it must be equivalent to:
291 * _pmd = *pmd; barrier();
292 *
293 * This is to deal with the instability (as in
294 * pmd_trans_unstable) of the pmd.
295 */
296 _pmd = READ_ONCE(*pmd);
297 if (!pmd_present(_pmd))
298 goto out;
299
300 ret = false;
301 if (pmd_trans_huge(_pmd))
302 goto out;
303
304 /*
305 * the pmd is stable (as in !pmd_trans_unstable) so we can re-read it
306 * and use the standard pte_offset_map() instead of parsing _pmd.
307 */
308 pte = pte_offset_map(pmd, address);
309 /*
310 * Lockless access: we're in a wait_event so it's ok if it
311 * changes under us.
312 */
313 if (pte_none(*pte))
314 ret = true;
315 pte_unmap(pte);
316
317out:
318 return ret;
319}
320
321/*
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700322 * The locking rules involved in returning VM_FAULT_RETRY depending on
323 * FAULT_FLAG_ALLOW_RETRY, FAULT_FLAG_RETRY_NOWAIT and
324 * FAULT_FLAG_KILLABLE are not straightforward. The "Caution"
325 * recommendation in __lock_page_or_retry is not an understatement.
326 *
327 * If FAULT_FLAG_ALLOW_RETRY is set, the mmap_sem must be released
328 * before returning VM_FAULT_RETRY only if FAULT_FLAG_RETRY_NOWAIT is
329 * not set.
330 *
331 * If FAULT_FLAG_ALLOW_RETRY is set but FAULT_FLAG_KILLABLE is not
332 * set, VM_FAULT_RETRY can still be returned if and only if there are
333 * fatal_signal_pending()s, and the mmap_sem must be released before
334 * returning it.
335 */
Jan Kara82b0f8c2016-12-14 15:06:58 -0800336int handle_userfault(struct vm_fault *vmf, unsigned long reason)
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700337{
Jan Kara82b0f8c2016-12-14 15:06:58 -0800338 struct mm_struct *mm = vmf->vma->vm_mm;
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700339 struct userfaultfd_ctx *ctx;
340 struct userfaultfd_wait_queue uwq;
Andrea Arcangeliba85c702015-09-04 15:46:41 -0700341 int ret;
Andrea Arcangelidfa37dc2015-09-04 15:47:18 -0700342 bool must_wait, return_to_userland;
Andrea Arcangeli15a77c62017-01-24 15:17:59 -0800343 long blocking_state;
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700344
Andrea Arcangeliba85c702015-09-04 15:46:41 -0700345 ret = VM_FAULT_SIGBUS;
Andrea Arcangeli64c2b202017-06-16 14:02:37 -0700346
347 /*
348 * We don't do userfault handling for the final child pid update.
349 *
350 * We also don't do userfault handling during
351 * coredumping. hugetlbfs has the special
352 * follow_hugetlb_page() to skip missing pages in the
353 * FOLL_DUMP case, anon memory also checks for FOLL_DUMP with
354 * the no_page_table() helper in follow_page_mask(), but the
355 * shmem_vm_ops->fault method is invoked even during
356 * coredumping without mmap_sem and it ends up here.
357 */
358 if (current->flags & (PF_EXITING|PF_DUMPCORE))
359 goto out;
360
361 /*
362 * Coredumping runs without mmap_sem so we can only check that
363 * the mmap_sem is held, if PF_DUMPCORE was not set.
364 */
365 WARN_ON_ONCE(!rwsem_is_locked(&mm->mmap_sem));
366
Jan Kara82b0f8c2016-12-14 15:06:58 -0800367 ctx = vmf->vma->vm_userfaultfd_ctx.ctx;
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700368 if (!ctx)
Andrea Arcangeliba85c702015-09-04 15:46:41 -0700369 goto out;
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700370
371 BUG_ON(ctx->mm != mm);
372
373 VM_BUG_ON(reason & ~(VM_UFFD_MISSING|VM_UFFD_WP));
374 VM_BUG_ON(!(reason & VM_UFFD_MISSING) ^ !!(reason & VM_UFFD_WP));
375
376 /*
377 * If it's already released don't get it. This avoids to loop
378 * in __get_user_pages if userfaultfd_release waits on the
379 * caller of handle_userfault to release the mmap_sem.
380 */
381 if (unlikely(ACCESS_ONCE(ctx->released)))
Andrea Arcangeliba85c702015-09-04 15:46:41 -0700382 goto out;
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700383
384 /*
385 * Check that we can return VM_FAULT_RETRY.
386 *
387 * NOTE: it should become possible to return VM_FAULT_RETRY
388 * even if FAULT_FLAG_TRIED is set without leading to gup()
389 * -EBUSY failures, if the userfaultfd is to be extended for
390 * VM_UFFD_WP tracking and we intend to arm the userfault
391 * without first stopping userland access to the memory. For
392 * VM_UFFD_MISSING userfaults this is enough for now.
393 */
Jan Kara82b0f8c2016-12-14 15:06:58 -0800394 if (unlikely(!(vmf->flags & FAULT_FLAG_ALLOW_RETRY))) {
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700395 /*
396 * Validate the invariant that nowait must allow retry
397 * to be sure not to return SIGBUS erroneously on
398 * nowait invocations.
399 */
Jan Kara82b0f8c2016-12-14 15:06:58 -0800400 BUG_ON(vmf->flags & FAULT_FLAG_RETRY_NOWAIT);
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700401#ifdef CONFIG_DEBUG_VM
402 if (printk_ratelimit()) {
403 printk(KERN_WARNING
Jan Kara82b0f8c2016-12-14 15:06:58 -0800404 "FAULT_FLAG_ALLOW_RETRY missing %x\n",
405 vmf->flags);
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700406 dump_stack();
407 }
408#endif
Andrea Arcangeliba85c702015-09-04 15:46:41 -0700409 goto out;
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700410 }
411
412 /*
413 * Handle nowait, not much to do other than tell it to retry
414 * and wait.
415 */
Andrea Arcangeliba85c702015-09-04 15:46:41 -0700416 ret = VM_FAULT_RETRY;
Jan Kara82b0f8c2016-12-14 15:06:58 -0800417 if (vmf->flags & FAULT_FLAG_RETRY_NOWAIT)
Andrea Arcangeliba85c702015-09-04 15:46:41 -0700418 goto out;
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700419
420 /* take the reference before dropping the mmap_sem */
421 userfaultfd_ctx_get(ctx);
422
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700423 init_waitqueue_func_entry(&uwq.wq, userfaultfd_wake_function);
424 uwq.wq.private = current;
Jan Kara82b0f8c2016-12-14 15:06:58 -0800425 uwq.msg = userfault_msg(vmf->address, vmf->flags, reason);
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700426 uwq.ctx = ctx;
Andrea Arcangeli15a77c62017-01-24 15:17:59 -0800427 uwq.waken = false;
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700428
Kirill A. Shutemovbae473a2016-07-26 15:25:20 -0700429 return_to_userland =
Jan Kara82b0f8c2016-12-14 15:06:58 -0800430 (vmf->flags & (FAULT_FLAG_USER|FAULT_FLAG_KILLABLE)) ==
Andrea Arcangelidfa37dc2015-09-04 15:47:18 -0700431 (FAULT_FLAG_USER|FAULT_FLAG_KILLABLE);
Andrea Arcangeli15a77c62017-01-24 15:17:59 -0800432 blocking_state = return_to_userland ? TASK_INTERRUPTIBLE :
433 TASK_KILLABLE;
Andrea Arcangelidfa37dc2015-09-04 15:47:18 -0700434
Andrea Arcangeli15b726e2015-09-04 15:46:44 -0700435 spin_lock(&ctx->fault_pending_wqh.lock);
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700436 /*
437 * After the __add_wait_queue the uwq is visible to userland
438 * through poll/read().
439 */
Andrea Arcangeli15b726e2015-09-04 15:46:44 -0700440 __add_wait_queue(&ctx->fault_pending_wqh, &uwq.wq);
441 /*
442 * The smp_mb() after __set_current_state prevents the reads
443 * following the spin_unlock to happen before the list_add in
444 * __add_wait_queue.
445 */
Andrea Arcangeli15a77c62017-01-24 15:17:59 -0800446 set_current_state(blocking_state);
Andrea Arcangeli15b726e2015-09-04 15:46:44 -0700447 spin_unlock(&ctx->fault_pending_wqh.lock);
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700448
Mike Kravetz369cd212017-02-22 15:43:10 -0800449 if (!is_vm_hugetlb_page(vmf->vma))
450 must_wait = userfaultfd_must_wait(ctx, vmf->address, vmf->flags,
451 reason);
452 else
Punit Agrawal7868a202017-07-06 15:39:42 -0700453 must_wait = userfaultfd_huge_must_wait(ctx, vmf->vma,
454 vmf->address,
Mike Kravetz369cd212017-02-22 15:43:10 -0800455 vmf->flags, reason);
Andrea Arcangeli8d2afd92015-09-04 15:46:51 -0700456 up_read(&mm->mmap_sem);
457
458 if (likely(must_wait && !ACCESS_ONCE(ctx->released) &&
Andrea Arcangelidfa37dc2015-09-04 15:47:18 -0700459 (return_to_userland ? !signal_pending(current) :
460 !fatal_signal_pending(current)))) {
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700461 wake_up_poll(&ctx->fd_wqh, POLLIN);
462 schedule();
Andrea Arcangeliba85c702015-09-04 15:46:41 -0700463 ret |= VM_FAULT_MAJOR;
Andrea Arcangeli15a77c62017-01-24 15:17:59 -0800464
465 /*
466 * False wakeups can orginate even from rwsem before
467 * up_read() however userfaults will wait either for a
468 * targeted wakeup on the specific uwq waitqueue from
469 * wake_userfault() or for signals or for uffd
470 * release.
471 */
472 while (!READ_ONCE(uwq.waken)) {
473 /*
474 * This needs the full smp_store_mb()
475 * guarantee as the state write must be
476 * visible to other CPUs before reading
477 * uwq.waken from other CPUs.
478 */
479 set_current_state(blocking_state);
480 if (READ_ONCE(uwq.waken) ||
481 READ_ONCE(ctx->released) ||
482 (return_to_userland ? signal_pending(current) :
483 fatal_signal_pending(current)))
484 break;
485 schedule();
486 }
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700487 }
Andrea Arcangeliba85c702015-09-04 15:46:41 -0700488
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700489 __set_current_state(TASK_RUNNING);
Andrea Arcangeli15b726e2015-09-04 15:46:44 -0700490
Andrea Arcangelidfa37dc2015-09-04 15:47:18 -0700491 if (return_to_userland) {
492 if (signal_pending(current) &&
493 !fatal_signal_pending(current)) {
494 /*
495 * If we got a SIGSTOP or SIGCONT and this is
496 * a normal userland page fault, just let
497 * userland return so the signal will be
498 * handled and gdb debugging works. The page
499 * fault code immediately after we return from
500 * this function is going to release the
501 * mmap_sem and it's not depending on it
502 * (unlike gup would if we were not to return
503 * VM_FAULT_RETRY).
504 *
505 * If a fatal signal is pending we still take
506 * the streamlined VM_FAULT_RETRY failure path
507 * and there's no need to retake the mmap_sem
508 * in such case.
509 */
510 down_read(&mm->mmap_sem);
Andrea Arcangeli6bbc4a42017-03-09 16:16:28 -0800511 ret = VM_FAULT_NOPAGE;
Andrea Arcangelidfa37dc2015-09-04 15:47:18 -0700512 }
513 }
514
Andrea Arcangeli15b726e2015-09-04 15:46:44 -0700515 /*
516 * Here we race with the list_del; list_add in
517 * userfaultfd_ctx_read(), however because we don't ever run
518 * list_del_init() to refile across the two lists, the prev
519 * and next pointers will never point to self. list_add also
520 * would never let any of the two pointers to point to
521 * self. So list_empty_careful won't risk to see both pointers
522 * pointing to self at any time during the list refile. The
523 * only case where list_del_init() is called is the full
524 * removal in the wake function and there we don't re-list_add
525 * and it's fine not to block on the spinlock. The uwq on this
526 * kernel stack can be released after the list_del_init.
527 */
Ingo Molnar2055da92017-06-20 12:06:46 +0200528 if (!list_empty_careful(&uwq.wq.entry)) {
Andrea Arcangeli15b726e2015-09-04 15:46:44 -0700529 spin_lock(&ctx->fault_pending_wqh.lock);
530 /*
531 * No need of list_del_init(), the uwq on the stack
532 * will be freed shortly anyway.
533 */
Ingo Molnar2055da92017-06-20 12:06:46 +0200534 list_del(&uwq.wq.entry);
Andrea Arcangeli15b726e2015-09-04 15:46:44 -0700535 spin_unlock(&ctx->fault_pending_wqh.lock);
Andrea Arcangeliba85c702015-09-04 15:46:41 -0700536 }
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700537
538 /*
539 * ctx may go away after this if the userfault pseudo fd is
540 * already released.
541 */
542 userfaultfd_ctx_put(ctx);
543
Andrea Arcangeliba85c702015-09-04 15:46:41 -0700544out:
545 return ret;
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700546}
547
Andrea Arcangeli8c9e7bb2017-03-09 16:16:54 -0800548static void userfaultfd_event_wait_completion(struct userfaultfd_ctx *ctx,
549 struct userfaultfd_wait_queue *ewq)
Pavel Emelyanov9cd75c32017-02-22 15:42:21 -0800550{
Andrea Arcangeli9a69a822017-03-09 16:16:52 -0800551 if (WARN_ON_ONCE(current->flags & PF_EXITING))
552 goto out;
553
Pavel Emelyanov9cd75c32017-02-22 15:42:21 -0800554 ewq->ctx = ctx;
555 init_waitqueue_entry(&ewq->wq, current);
556
557 spin_lock(&ctx->event_wqh.lock);
558 /*
559 * After the __add_wait_queue the uwq is visible to userland
560 * through poll/read().
561 */
562 __add_wait_queue(&ctx->event_wqh, &ewq->wq);
563 for (;;) {
564 set_current_state(TASK_KILLABLE);
565 if (ewq->msg.event == 0)
566 break;
567 if (ACCESS_ONCE(ctx->released) ||
568 fatal_signal_pending(current)) {
Pavel Emelyanov9cd75c32017-02-22 15:42:21 -0800569 __remove_wait_queue(&ctx->event_wqh, &ewq->wq);
Mike Rapoport7eb76d42017-03-09 16:17:09 -0800570 if (ewq->msg.event == UFFD_EVENT_FORK) {
571 struct userfaultfd_ctx *new;
572
573 new = (struct userfaultfd_ctx *)
574 (unsigned long)
575 ewq->msg.arg.reserved.reserved1;
576
577 userfaultfd_ctx_put(new);
578 }
Pavel Emelyanov9cd75c32017-02-22 15:42:21 -0800579 break;
580 }
581
582 spin_unlock(&ctx->event_wqh.lock);
583
584 wake_up_poll(&ctx->fd_wqh, POLLIN);
585 schedule();
586
587 spin_lock(&ctx->event_wqh.lock);
588 }
589 __set_current_state(TASK_RUNNING);
590 spin_unlock(&ctx->event_wqh.lock);
591
592 /*
593 * ctx may go away after this if the userfault pseudo fd is
594 * already released.
595 */
Andrea Arcangeli9a69a822017-03-09 16:16:52 -0800596out:
Pavel Emelyanov9cd75c32017-02-22 15:42:21 -0800597 userfaultfd_ctx_put(ctx);
Pavel Emelyanov9cd75c32017-02-22 15:42:21 -0800598}
599
600static void userfaultfd_event_complete(struct userfaultfd_ctx *ctx,
601 struct userfaultfd_wait_queue *ewq)
602{
603 ewq->msg.event = 0;
604 wake_up_locked(&ctx->event_wqh);
605 __remove_wait_queue(&ctx->event_wqh, &ewq->wq);
606}
607
Pavel Emelyanov893e26e2017-02-22 15:42:27 -0800608int dup_userfaultfd(struct vm_area_struct *vma, struct list_head *fcs)
609{
610 struct userfaultfd_ctx *ctx = NULL, *octx;
611 struct userfaultfd_fork_ctx *fctx;
612
613 octx = vma->vm_userfaultfd_ctx.ctx;
614 if (!octx || !(octx->features & UFFD_FEATURE_EVENT_FORK)) {
615 vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX;
616 vma->vm_flags &= ~(VM_UFFD_WP | VM_UFFD_MISSING);
617 return 0;
618 }
619
620 list_for_each_entry(fctx, fcs, list)
621 if (fctx->orig == octx) {
622 ctx = fctx->new;
623 break;
624 }
625
626 if (!ctx) {
627 fctx = kmalloc(sizeof(*fctx), GFP_KERNEL);
628 if (!fctx)
629 return -ENOMEM;
630
631 ctx = kmem_cache_alloc(userfaultfd_ctx_cachep, GFP_KERNEL);
632 if (!ctx) {
633 kfree(fctx);
634 return -ENOMEM;
635 }
636
637 atomic_set(&ctx->refcount, 1);
638 ctx->flags = octx->flags;
639 ctx->state = UFFD_STATE_RUNNING;
640 ctx->features = octx->features;
641 ctx->released = false;
642 ctx->mm = vma->vm_mm;
Mike Rapoportd3aadc82017-02-22 15:42:30 -0800643 atomic_inc(&ctx->mm->mm_count);
Pavel Emelyanov893e26e2017-02-22 15:42:27 -0800644
645 userfaultfd_ctx_get(octx);
646 fctx->orig = octx;
647 fctx->new = ctx;
648 list_add_tail(&fctx->list, fcs);
649 }
650
651 vma->vm_userfaultfd_ctx.ctx = ctx;
652 return 0;
653}
654
Andrea Arcangeli8c9e7bb2017-03-09 16:16:54 -0800655static void dup_fctx(struct userfaultfd_fork_ctx *fctx)
Pavel Emelyanov893e26e2017-02-22 15:42:27 -0800656{
657 struct userfaultfd_ctx *ctx = fctx->orig;
658 struct userfaultfd_wait_queue ewq;
659
660 msg_init(&ewq.msg);
661
662 ewq.msg.event = UFFD_EVENT_FORK;
663 ewq.msg.arg.reserved.reserved1 = (unsigned long)fctx->new;
664
Andrea Arcangeli8c9e7bb2017-03-09 16:16:54 -0800665 userfaultfd_event_wait_completion(ctx, &ewq);
Pavel Emelyanov893e26e2017-02-22 15:42:27 -0800666}
667
668void dup_userfaultfd_complete(struct list_head *fcs)
669{
Pavel Emelyanov893e26e2017-02-22 15:42:27 -0800670 struct userfaultfd_fork_ctx *fctx, *n;
671
672 list_for_each_entry_safe(fctx, n, fcs, list) {
Andrea Arcangeli8c9e7bb2017-03-09 16:16:54 -0800673 dup_fctx(fctx);
Pavel Emelyanov893e26e2017-02-22 15:42:27 -0800674 list_del(&fctx->list);
675 kfree(fctx);
676 }
677}
678
Pavel Emelyanov72f87652017-02-22 15:42:34 -0800679void mremap_userfaultfd_prep(struct vm_area_struct *vma,
680 struct vm_userfaultfd_ctx *vm_ctx)
681{
682 struct userfaultfd_ctx *ctx;
683
684 ctx = vma->vm_userfaultfd_ctx.ctx;
685 if (ctx && (ctx->features & UFFD_FEATURE_EVENT_REMAP)) {
686 vm_ctx->ctx = ctx;
687 userfaultfd_ctx_get(ctx);
688 }
689}
690
Andrea Arcangeli90794bf2017-02-22 15:42:37 -0800691void mremap_userfaultfd_complete(struct vm_userfaultfd_ctx *vm_ctx,
Pavel Emelyanov72f87652017-02-22 15:42:34 -0800692 unsigned long from, unsigned long to,
693 unsigned long len)
694{
Andrea Arcangeli90794bf2017-02-22 15:42:37 -0800695 struct userfaultfd_ctx *ctx = vm_ctx->ctx;
Pavel Emelyanov72f87652017-02-22 15:42:34 -0800696 struct userfaultfd_wait_queue ewq;
697
698 if (!ctx)
699 return;
700
701 if (to & ~PAGE_MASK) {
702 userfaultfd_ctx_put(ctx);
703 return;
704 }
705
706 msg_init(&ewq.msg);
707
708 ewq.msg.event = UFFD_EVENT_REMAP;
709 ewq.msg.arg.remap.from = from;
710 ewq.msg.arg.remap.to = to;
711 ewq.msg.arg.remap.len = len;
712
713 userfaultfd_event_wait_completion(ctx, &ewq);
714}
715
Andrea Arcangeli70ccb922017-03-09 16:17:11 -0800716bool userfaultfd_remove(struct vm_area_struct *vma,
Mike Rapoportd8119142017-02-24 14:56:02 -0800717 unsigned long start, unsigned long end)
Pavel Emelyanov05ce7722017-02-22 15:42:40 -0800718{
719 struct mm_struct *mm = vma->vm_mm;
720 struct userfaultfd_ctx *ctx;
721 struct userfaultfd_wait_queue ewq;
722
723 ctx = vma->vm_userfaultfd_ctx.ctx;
Mike Rapoportd8119142017-02-24 14:56:02 -0800724 if (!ctx || !(ctx->features & UFFD_FEATURE_EVENT_REMOVE))
Andrea Arcangeli70ccb922017-03-09 16:17:11 -0800725 return true;
Pavel Emelyanov05ce7722017-02-22 15:42:40 -0800726
727 userfaultfd_ctx_get(ctx);
728 up_read(&mm->mmap_sem);
729
Pavel Emelyanov05ce7722017-02-22 15:42:40 -0800730 msg_init(&ewq.msg);
731
Mike Rapoportd8119142017-02-24 14:56:02 -0800732 ewq.msg.event = UFFD_EVENT_REMOVE;
733 ewq.msg.arg.remove.start = start;
734 ewq.msg.arg.remove.end = end;
Pavel Emelyanov05ce7722017-02-22 15:42:40 -0800735
736 userfaultfd_event_wait_completion(ctx, &ewq);
737
Andrea Arcangeli70ccb922017-03-09 16:17:11 -0800738 return false;
Pavel Emelyanov05ce7722017-02-22 15:42:40 -0800739}
740
Mike Rapoport897ab3e2017-02-24 14:58:22 -0800741static bool has_unmap_ctx(struct userfaultfd_ctx *ctx, struct list_head *unmaps,
742 unsigned long start, unsigned long end)
743{
744 struct userfaultfd_unmap_ctx *unmap_ctx;
745
746 list_for_each_entry(unmap_ctx, unmaps, list)
747 if (unmap_ctx->ctx == ctx && unmap_ctx->start == start &&
748 unmap_ctx->end == end)
749 return true;
750
751 return false;
752}
753
754int userfaultfd_unmap_prep(struct vm_area_struct *vma,
755 unsigned long start, unsigned long end,
756 struct list_head *unmaps)
757{
758 for ( ; vma && vma->vm_start < end; vma = vma->vm_next) {
759 struct userfaultfd_unmap_ctx *unmap_ctx;
760 struct userfaultfd_ctx *ctx = vma->vm_userfaultfd_ctx.ctx;
761
762 if (!ctx || !(ctx->features & UFFD_FEATURE_EVENT_UNMAP) ||
763 has_unmap_ctx(ctx, unmaps, start, end))
764 continue;
765
766 unmap_ctx = kzalloc(sizeof(*unmap_ctx), GFP_KERNEL);
767 if (!unmap_ctx)
768 return -ENOMEM;
769
770 userfaultfd_ctx_get(ctx);
771 unmap_ctx->ctx = ctx;
772 unmap_ctx->start = start;
773 unmap_ctx->end = end;
774 list_add_tail(&unmap_ctx->list, unmaps);
775 }
776
777 return 0;
778}
779
780void userfaultfd_unmap_complete(struct mm_struct *mm, struct list_head *uf)
781{
782 struct userfaultfd_unmap_ctx *ctx, *n;
783 struct userfaultfd_wait_queue ewq;
784
785 list_for_each_entry_safe(ctx, n, uf, list) {
786 msg_init(&ewq.msg);
787
788 ewq.msg.event = UFFD_EVENT_UNMAP;
789 ewq.msg.arg.remove.start = ctx->start;
790 ewq.msg.arg.remove.end = ctx->end;
791
792 userfaultfd_event_wait_completion(ctx->ctx, &ewq);
793
794 list_del(&ctx->list);
795 kfree(ctx);
796 }
797}
798
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700799static int userfaultfd_release(struct inode *inode, struct file *file)
800{
801 struct userfaultfd_ctx *ctx = file->private_data;
802 struct mm_struct *mm = ctx->mm;
803 struct vm_area_struct *vma, *prev;
804 /* len == 0 means wake all */
805 struct userfaultfd_wake_range range = { .len = 0, };
806 unsigned long new_flags;
807
808 ACCESS_ONCE(ctx->released) = true;
809
Oleg Nesterovd2005e32016-05-20 16:58:36 -0700810 if (!mmget_not_zero(mm))
811 goto wakeup;
812
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700813 /*
814 * Flush page faults out of all CPUs. NOTE: all page faults
815 * must be retried without returning VM_FAULT_SIGBUS if
816 * userfaultfd_ctx_get() succeeds but vma->vma_userfault_ctx
817 * changes while handle_userfault released the mmap_sem. So
818 * it's critical that released is set to true (above), before
819 * taking the mmap_sem for writing.
820 */
821 down_write(&mm->mmap_sem);
822 prev = NULL;
823 for (vma = mm->mmap; vma; vma = vma->vm_next) {
824 cond_resched();
825 BUG_ON(!!vma->vm_userfaultfd_ctx.ctx ^
826 !!(vma->vm_flags & (VM_UFFD_MISSING | VM_UFFD_WP)));
827 if (vma->vm_userfaultfd_ctx.ctx != ctx) {
828 prev = vma;
829 continue;
830 }
831 new_flags = vma->vm_flags & ~(VM_UFFD_MISSING | VM_UFFD_WP);
832 prev = vma_merge(mm, prev, vma->vm_start, vma->vm_end,
833 new_flags, vma->anon_vma,
834 vma->vm_file, vma->vm_pgoff,
835 vma_policy(vma),
836 NULL_VM_UFFD_CTX);
837 if (prev)
838 vma = prev;
839 else
840 prev = vma;
841 vma->vm_flags = new_flags;
842 vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX;
843 }
844 up_write(&mm->mmap_sem);
Oleg Nesterovd2005e32016-05-20 16:58:36 -0700845 mmput(mm);
846wakeup:
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700847 /*
Andrea Arcangeli15b726e2015-09-04 15:46:44 -0700848 * After no new page faults can wait on this fault_*wqh, flush
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700849 * the last page faults that may have been already waiting on
Andrea Arcangeli15b726e2015-09-04 15:46:44 -0700850 * the fault_*wqh.
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700851 */
Andrea Arcangeli15b726e2015-09-04 15:46:44 -0700852 spin_lock(&ctx->fault_pending_wqh.lock);
Andrea Arcangeliac5be6b2015-09-22 14:58:49 -0700853 __wake_up_locked_key(&ctx->fault_pending_wqh, TASK_NORMAL, &range);
854 __wake_up_locked_key(&ctx->fault_wqh, TASK_NORMAL, &range);
Andrea Arcangeli15b726e2015-09-04 15:46:44 -0700855 spin_unlock(&ctx->fault_pending_wqh.lock);
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700856
857 wake_up_poll(&ctx->fd_wqh, POLLHUP);
858 userfaultfd_ctx_put(ctx);
859 return 0;
860}
861
Andrea Arcangeli15b726e2015-09-04 15:46:44 -0700862/* fault_pending_wqh.lock must be hold by the caller */
Pavel Emelyanov6dcc27f2017-02-22 15:42:18 -0800863static inline struct userfaultfd_wait_queue *find_userfault_in(
864 wait_queue_head_t *wqh)
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700865{
Ingo Molnarac6424b2017-06-20 12:06:13 +0200866 wait_queue_entry_t *wq;
Andrea Arcangeli15b726e2015-09-04 15:46:44 -0700867 struct userfaultfd_wait_queue *uwq;
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700868
Pavel Emelyanov6dcc27f2017-02-22 15:42:18 -0800869 VM_BUG_ON(!spin_is_locked(&wqh->lock));
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700870
Andrea Arcangeli15b726e2015-09-04 15:46:44 -0700871 uwq = NULL;
Pavel Emelyanov6dcc27f2017-02-22 15:42:18 -0800872 if (!waitqueue_active(wqh))
Andrea Arcangeli15b726e2015-09-04 15:46:44 -0700873 goto out;
874 /* walk in reverse to provide FIFO behavior to read userfaults */
Ingo Molnar2055da92017-06-20 12:06:46 +0200875 wq = list_last_entry(&wqh->head, typeof(*wq), entry);
Andrea Arcangeli15b726e2015-09-04 15:46:44 -0700876 uwq = container_of(wq, struct userfaultfd_wait_queue, wq);
877out:
878 return uwq;
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700879}
880
Pavel Emelyanov6dcc27f2017-02-22 15:42:18 -0800881static inline struct userfaultfd_wait_queue *find_userfault(
882 struct userfaultfd_ctx *ctx)
883{
884 return find_userfault_in(&ctx->fault_pending_wqh);
885}
886
Pavel Emelyanov9cd75c32017-02-22 15:42:21 -0800887static inline struct userfaultfd_wait_queue *find_userfault_evt(
888 struct userfaultfd_ctx *ctx)
889{
890 return find_userfault_in(&ctx->event_wqh);
891}
892
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700893static unsigned int userfaultfd_poll(struct file *file, poll_table *wait)
894{
895 struct userfaultfd_ctx *ctx = file->private_data;
896 unsigned int ret;
897
898 poll_wait(file, &ctx->fd_wqh, wait);
899
900 switch (ctx->state) {
901 case UFFD_STATE_WAIT_API:
902 return POLLERR;
903 case UFFD_STATE_RUNNING:
Andrea Arcangeliba85c702015-09-04 15:46:41 -0700904 /*
905 * poll() never guarantees that read won't block.
906 * userfaults can be waken before they're read().
907 */
908 if (unlikely(!(file->f_flags & O_NONBLOCK)))
909 return POLLERR;
Andrea Arcangeli15b726e2015-09-04 15:46:44 -0700910 /*
911 * lockless access to see if there are pending faults
912 * __pollwait last action is the add_wait_queue but
913 * the spin_unlock would allow the waitqueue_active to
914 * pass above the actual list_add inside
915 * add_wait_queue critical section. So use a full
916 * memory barrier to serialize the list_add write of
917 * add_wait_queue() with the waitqueue_active read
918 * below.
919 */
920 ret = 0;
921 smp_mb();
922 if (waitqueue_active(&ctx->fault_pending_wqh))
923 ret = POLLIN;
Pavel Emelyanov9cd75c32017-02-22 15:42:21 -0800924 else if (waitqueue_active(&ctx->event_wqh))
925 ret = POLLIN;
926
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700927 return ret;
928 default:
Andrea Arcangeli84749012017-02-22 15:42:12 -0800929 WARN_ON_ONCE(1);
930 return POLLERR;
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700931 }
932}
933
Pavel Emelyanov893e26e2017-02-22 15:42:27 -0800934static const struct file_operations userfaultfd_fops;
935
936static int resolve_userfault_fork(struct userfaultfd_ctx *ctx,
937 struct userfaultfd_ctx *new,
938 struct uffd_msg *msg)
939{
940 int fd;
941 struct file *file;
942 unsigned int flags = new->flags & UFFD_SHARED_FCNTL_FLAGS;
943
944 fd = get_unused_fd_flags(flags);
945 if (fd < 0)
946 return fd;
947
948 file = anon_inode_getfile("[userfaultfd]", &userfaultfd_fops, new,
949 O_RDWR | flags);
950 if (IS_ERR(file)) {
951 put_unused_fd(fd);
952 return PTR_ERR(file);
953 }
954
955 fd_install(fd, file);
956 msg->arg.reserved.reserved1 = 0;
957 msg->arg.fork.ufd = fd;
958
959 return 0;
960}
961
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700962static ssize_t userfaultfd_ctx_read(struct userfaultfd_ctx *ctx, int no_wait,
Andrea Arcangelia9b85f92015-09-04 15:46:37 -0700963 struct uffd_msg *msg)
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700964{
965 ssize_t ret;
966 DECLARE_WAITQUEUE(wait, current);
Andrea Arcangeli15b726e2015-09-04 15:46:44 -0700967 struct userfaultfd_wait_queue *uwq;
Pavel Emelyanov893e26e2017-02-22 15:42:27 -0800968 /*
969 * Handling fork event requires sleeping operations, so
970 * we drop the event_wqh lock, then do these ops, then
971 * lock it back and wake up the waiter. While the lock is
972 * dropped the ewq may go away so we keep track of it
973 * carefully.
974 */
975 LIST_HEAD(fork_event);
976 struct userfaultfd_ctx *fork_nctx = NULL;
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700977
Andrea Arcangeli15b726e2015-09-04 15:46:44 -0700978 /* always take the fd_wqh lock before the fault_pending_wqh lock */
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700979 spin_lock(&ctx->fd_wqh.lock);
980 __add_wait_queue(&ctx->fd_wqh, &wait);
981 for (;;) {
982 set_current_state(TASK_INTERRUPTIBLE);
Andrea Arcangeli15b726e2015-09-04 15:46:44 -0700983 spin_lock(&ctx->fault_pending_wqh.lock);
984 uwq = find_userfault(ctx);
985 if (uwq) {
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700986 /*
Andrea Arcangeli2c5b7e12015-09-04 15:47:23 -0700987 * Use a seqcount to repeat the lockless check
988 * in wake_userfault() to avoid missing
989 * wakeups because during the refile both
990 * waitqueue could become empty if this is the
991 * only userfault.
992 */
993 write_seqcount_begin(&ctx->refile_seq);
994
995 /*
Andrea Arcangeli15b726e2015-09-04 15:46:44 -0700996 * The fault_pending_wqh.lock prevents the uwq
997 * to disappear from under us.
998 *
999 * Refile this userfault from
1000 * fault_pending_wqh to fault_wqh, it's not
1001 * pending anymore after we read it.
1002 *
1003 * Use list_del() by hand (as
1004 * userfaultfd_wake_function also uses
1005 * list_del_init() by hand) to be sure nobody
1006 * changes __remove_wait_queue() to use
1007 * list_del_init() in turn breaking the
1008 * !list_empty_careful() check in
Ingo Molnar2055da92017-06-20 12:06:46 +02001009 * handle_userfault(). The uwq->wq.head list
Andrea Arcangeli15b726e2015-09-04 15:46:44 -07001010 * must never be empty at any time during the
1011 * refile, or the waitqueue could disappear
1012 * from under us. The "wait_queue_head_t"
1013 * parameter of __remove_wait_queue() is unused
1014 * anyway.
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001015 */
Ingo Molnar2055da92017-06-20 12:06:46 +02001016 list_del(&uwq->wq.entry);
Andrea Arcangeli15b726e2015-09-04 15:46:44 -07001017 __add_wait_queue(&ctx->fault_wqh, &uwq->wq);
1018
Andrea Arcangeli2c5b7e12015-09-04 15:47:23 -07001019 write_seqcount_end(&ctx->refile_seq);
1020
Andrea Arcangelia9b85f92015-09-04 15:46:37 -07001021 /* careful to always initialize msg if ret == 0 */
1022 *msg = uwq->msg;
Andrea Arcangeli15b726e2015-09-04 15:46:44 -07001023 spin_unlock(&ctx->fault_pending_wqh.lock);
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001024 ret = 0;
1025 break;
1026 }
Andrea Arcangeli15b726e2015-09-04 15:46:44 -07001027 spin_unlock(&ctx->fault_pending_wqh.lock);
Pavel Emelyanov9cd75c32017-02-22 15:42:21 -08001028
1029 spin_lock(&ctx->event_wqh.lock);
1030 uwq = find_userfault_evt(ctx);
1031 if (uwq) {
1032 *msg = uwq->msg;
1033
Pavel Emelyanov893e26e2017-02-22 15:42:27 -08001034 if (uwq->msg.event == UFFD_EVENT_FORK) {
1035 fork_nctx = (struct userfaultfd_ctx *)
1036 (unsigned long)
1037 uwq->msg.arg.reserved.reserved1;
Ingo Molnar2055da92017-06-20 12:06:46 +02001038 list_move(&uwq->wq.entry, &fork_event);
Pavel Emelyanov893e26e2017-02-22 15:42:27 -08001039 spin_unlock(&ctx->event_wqh.lock);
1040 ret = 0;
1041 break;
1042 }
1043
Pavel Emelyanov9cd75c32017-02-22 15:42:21 -08001044 userfaultfd_event_complete(ctx, uwq);
1045 spin_unlock(&ctx->event_wqh.lock);
1046 ret = 0;
1047 break;
1048 }
1049 spin_unlock(&ctx->event_wqh.lock);
1050
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001051 if (signal_pending(current)) {
1052 ret = -ERESTARTSYS;
1053 break;
1054 }
1055 if (no_wait) {
1056 ret = -EAGAIN;
1057 break;
1058 }
1059 spin_unlock(&ctx->fd_wqh.lock);
1060 schedule();
1061 spin_lock(&ctx->fd_wqh.lock);
1062 }
1063 __remove_wait_queue(&ctx->fd_wqh, &wait);
1064 __set_current_state(TASK_RUNNING);
1065 spin_unlock(&ctx->fd_wqh.lock);
1066
Pavel Emelyanov893e26e2017-02-22 15:42:27 -08001067 if (!ret && msg->event == UFFD_EVENT_FORK) {
1068 ret = resolve_userfault_fork(ctx, fork_nctx, msg);
1069
1070 if (!ret) {
1071 spin_lock(&ctx->event_wqh.lock);
1072 if (!list_empty(&fork_event)) {
1073 uwq = list_first_entry(&fork_event,
1074 typeof(*uwq),
Ingo Molnar2055da92017-06-20 12:06:46 +02001075 wq.entry);
1076 list_del(&uwq->wq.entry);
Pavel Emelyanov893e26e2017-02-22 15:42:27 -08001077 __add_wait_queue(&ctx->event_wqh, &uwq->wq);
1078 userfaultfd_event_complete(ctx, uwq);
1079 }
1080 spin_unlock(&ctx->event_wqh.lock);
1081 }
1082 }
1083
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001084 return ret;
1085}
1086
1087static ssize_t userfaultfd_read(struct file *file, char __user *buf,
1088 size_t count, loff_t *ppos)
1089{
1090 struct userfaultfd_ctx *ctx = file->private_data;
1091 ssize_t _ret, ret = 0;
Andrea Arcangelia9b85f92015-09-04 15:46:37 -07001092 struct uffd_msg msg;
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001093 int no_wait = file->f_flags & O_NONBLOCK;
1094
1095 if (ctx->state == UFFD_STATE_WAIT_API)
1096 return -EINVAL;
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001097
1098 for (;;) {
Andrea Arcangelia9b85f92015-09-04 15:46:37 -07001099 if (count < sizeof(msg))
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001100 return ret ? ret : -EINVAL;
Andrea Arcangelia9b85f92015-09-04 15:46:37 -07001101 _ret = userfaultfd_ctx_read(ctx, no_wait, &msg);
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001102 if (_ret < 0)
1103 return ret ? ret : _ret;
Andrea Arcangelia9b85f92015-09-04 15:46:37 -07001104 if (copy_to_user((__u64 __user *) buf, &msg, sizeof(msg)))
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001105 return ret ? ret : -EFAULT;
Andrea Arcangelia9b85f92015-09-04 15:46:37 -07001106 ret += sizeof(msg);
1107 buf += sizeof(msg);
1108 count -= sizeof(msg);
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001109 /*
1110 * Allow to read more than one fault at time but only
1111 * block if waiting for the very first one.
1112 */
1113 no_wait = O_NONBLOCK;
1114 }
1115}
1116
1117static void __wake_userfault(struct userfaultfd_ctx *ctx,
1118 struct userfaultfd_wake_range *range)
1119{
Andrea Arcangeli15b726e2015-09-04 15:46:44 -07001120 spin_lock(&ctx->fault_pending_wqh.lock);
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001121 /* wake all in the range and autoremove */
Andrea Arcangeli15b726e2015-09-04 15:46:44 -07001122 if (waitqueue_active(&ctx->fault_pending_wqh))
Andrea Arcangeliac5be6b2015-09-22 14:58:49 -07001123 __wake_up_locked_key(&ctx->fault_pending_wqh, TASK_NORMAL,
Andrea Arcangeli15b726e2015-09-04 15:46:44 -07001124 range);
1125 if (waitqueue_active(&ctx->fault_wqh))
Andrea Arcangeliac5be6b2015-09-22 14:58:49 -07001126 __wake_up_locked_key(&ctx->fault_wqh, TASK_NORMAL, range);
Andrea Arcangeli15b726e2015-09-04 15:46:44 -07001127 spin_unlock(&ctx->fault_pending_wqh.lock);
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001128}
1129
1130static __always_inline void wake_userfault(struct userfaultfd_ctx *ctx,
1131 struct userfaultfd_wake_range *range)
1132{
Andrea Arcangeli2c5b7e12015-09-04 15:47:23 -07001133 unsigned seq;
1134 bool need_wakeup;
1135
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001136 /*
1137 * To be sure waitqueue_active() is not reordered by the CPU
1138 * before the pagetable update, use an explicit SMP memory
1139 * barrier here. PT lock release or up_read(mmap_sem) still
1140 * have release semantics that can allow the
1141 * waitqueue_active() to be reordered before the pte update.
1142 */
1143 smp_mb();
1144
1145 /*
1146 * Use waitqueue_active because it's very frequent to
1147 * change the address space atomically even if there are no
1148 * userfaults yet. So we take the spinlock only when we're
1149 * sure we've userfaults to wake.
1150 */
Andrea Arcangeli2c5b7e12015-09-04 15:47:23 -07001151 do {
1152 seq = read_seqcount_begin(&ctx->refile_seq);
1153 need_wakeup = waitqueue_active(&ctx->fault_pending_wqh) ||
1154 waitqueue_active(&ctx->fault_wqh);
1155 cond_resched();
1156 } while (read_seqcount_retry(&ctx->refile_seq, seq));
1157 if (need_wakeup)
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001158 __wake_userfault(ctx, range);
1159}
1160
1161static __always_inline int validate_range(struct mm_struct *mm,
1162 __u64 start, __u64 len)
1163{
1164 __u64 task_size = mm->task_size;
1165
1166 if (start & ~PAGE_MASK)
1167 return -EINVAL;
1168 if (len & ~PAGE_MASK)
1169 return -EINVAL;
1170 if (!len)
1171 return -EINVAL;
1172 if (start < mmap_min_addr)
1173 return -EINVAL;
1174 if (start >= task_size)
1175 return -EINVAL;
1176 if (len > task_size - start)
1177 return -EINVAL;
1178 return 0;
1179}
1180
Mike Rapoportba6907d2017-02-22 15:43:22 -08001181static inline bool vma_can_userfault(struct vm_area_struct *vma)
1182{
Mike Rapoportcac67322017-02-22 15:43:40 -08001183 return vma_is_anonymous(vma) || is_vm_hugetlb_page(vma) ||
1184 vma_is_shmem(vma);
Mike Rapoportba6907d2017-02-22 15:43:22 -08001185}
1186
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001187static int userfaultfd_register(struct userfaultfd_ctx *ctx,
1188 unsigned long arg)
1189{
1190 struct mm_struct *mm = ctx->mm;
1191 struct vm_area_struct *vma, *prev, *cur;
1192 int ret;
1193 struct uffdio_register uffdio_register;
1194 struct uffdio_register __user *user_uffdio_register;
1195 unsigned long vm_flags, new_flags;
1196 bool found;
Mike Rapoportcac67322017-02-22 15:43:40 -08001197 bool non_anon_pages;
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001198 unsigned long start, end, vma_end;
1199
1200 user_uffdio_register = (struct uffdio_register __user *) arg;
1201
1202 ret = -EFAULT;
1203 if (copy_from_user(&uffdio_register, user_uffdio_register,
1204 sizeof(uffdio_register)-sizeof(__u64)))
1205 goto out;
1206
1207 ret = -EINVAL;
1208 if (!uffdio_register.mode)
1209 goto out;
1210 if (uffdio_register.mode & ~(UFFDIO_REGISTER_MODE_MISSING|
1211 UFFDIO_REGISTER_MODE_WP))
1212 goto out;
1213 vm_flags = 0;
1214 if (uffdio_register.mode & UFFDIO_REGISTER_MODE_MISSING)
1215 vm_flags |= VM_UFFD_MISSING;
1216 if (uffdio_register.mode & UFFDIO_REGISTER_MODE_WP) {
1217 vm_flags |= VM_UFFD_WP;
1218 /*
1219 * FIXME: remove the below error constraint by
1220 * implementing the wprotect tracking mode.
1221 */
1222 ret = -EINVAL;
1223 goto out;
1224 }
1225
1226 ret = validate_range(mm, uffdio_register.range.start,
1227 uffdio_register.range.len);
1228 if (ret)
1229 goto out;
1230
1231 start = uffdio_register.range.start;
1232 end = start + uffdio_register.range.len;
1233
Oleg Nesterovd2005e32016-05-20 16:58:36 -07001234 ret = -ENOMEM;
1235 if (!mmget_not_zero(mm))
1236 goto out;
1237
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001238 down_write(&mm->mmap_sem);
1239 vma = find_vma_prev(mm, start, &prev);
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001240 if (!vma)
1241 goto out_unlock;
1242
1243 /* check that there's at least one vma in the range */
1244 ret = -EINVAL;
1245 if (vma->vm_start >= end)
1246 goto out_unlock;
1247
1248 /*
Mike Kravetzcab350a2017-02-22 15:43:04 -08001249 * If the first vma contains huge pages, make sure start address
1250 * is aligned to huge page size.
1251 */
1252 if (is_vm_hugetlb_page(vma)) {
1253 unsigned long vma_hpagesize = vma_kernel_pagesize(vma);
1254
1255 if (start & (vma_hpagesize - 1))
1256 goto out_unlock;
1257 }
1258
1259 /*
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001260 * Search for not compatible vmas.
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001261 */
1262 found = false;
Mike Rapoportcac67322017-02-22 15:43:40 -08001263 non_anon_pages = false;
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001264 for (cur = vma; cur && cur->vm_start < end; cur = cur->vm_next) {
1265 cond_resched();
1266
1267 BUG_ON(!!cur->vm_userfaultfd_ctx.ctx ^
1268 !!(cur->vm_flags & (VM_UFFD_MISSING | VM_UFFD_WP)));
1269
1270 /* check not compatible vmas */
1271 ret = -EINVAL;
Mike Rapoportba6907d2017-02-22 15:43:22 -08001272 if (!vma_can_userfault(cur))
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001273 goto out_unlock;
Mike Kravetzcab350a2017-02-22 15:43:04 -08001274 /*
1275 * If this vma contains ending address, and huge pages
1276 * check alignment.
1277 */
1278 if (is_vm_hugetlb_page(cur) && end <= cur->vm_end &&
1279 end > cur->vm_start) {
1280 unsigned long vma_hpagesize = vma_kernel_pagesize(cur);
1281
1282 ret = -EINVAL;
1283
1284 if (end & (vma_hpagesize - 1))
1285 goto out_unlock;
1286 }
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001287
1288 /*
1289 * Check that this vma isn't already owned by a
1290 * different userfaultfd. We can't allow more than one
1291 * userfaultfd to own a single vma simultaneously or we
1292 * wouldn't know which one to deliver the userfaults to.
1293 */
1294 ret = -EBUSY;
1295 if (cur->vm_userfaultfd_ctx.ctx &&
1296 cur->vm_userfaultfd_ctx.ctx != ctx)
1297 goto out_unlock;
1298
Mike Kravetzcab350a2017-02-22 15:43:04 -08001299 /*
1300 * Note vmas containing huge pages
1301 */
Mike Rapoportcac67322017-02-22 15:43:40 -08001302 if (is_vm_hugetlb_page(cur) || vma_is_shmem(cur))
1303 non_anon_pages = true;
Mike Kravetzcab350a2017-02-22 15:43:04 -08001304
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001305 found = true;
1306 }
1307 BUG_ON(!found);
1308
1309 if (vma->vm_start < start)
1310 prev = vma;
1311
1312 ret = 0;
1313 do {
1314 cond_resched();
1315
Mike Rapoportba6907d2017-02-22 15:43:22 -08001316 BUG_ON(!vma_can_userfault(vma));
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001317 BUG_ON(vma->vm_userfaultfd_ctx.ctx &&
1318 vma->vm_userfaultfd_ctx.ctx != ctx);
1319
1320 /*
1321 * Nothing to do: this vma is already registered into this
1322 * userfaultfd and with the right tracking mode too.
1323 */
1324 if (vma->vm_userfaultfd_ctx.ctx == ctx &&
1325 (vma->vm_flags & vm_flags) == vm_flags)
1326 goto skip;
1327
1328 if (vma->vm_start > start)
1329 start = vma->vm_start;
1330 vma_end = min(end, vma->vm_end);
1331
1332 new_flags = (vma->vm_flags & ~vm_flags) | vm_flags;
1333 prev = vma_merge(mm, prev, start, vma_end, new_flags,
1334 vma->anon_vma, vma->vm_file, vma->vm_pgoff,
1335 vma_policy(vma),
1336 ((struct vm_userfaultfd_ctx){ ctx }));
1337 if (prev) {
1338 vma = prev;
1339 goto next;
1340 }
1341 if (vma->vm_start < start) {
1342 ret = split_vma(mm, vma, start, 1);
1343 if (ret)
1344 break;
1345 }
1346 if (vma->vm_end > end) {
1347 ret = split_vma(mm, vma, end, 0);
1348 if (ret)
1349 break;
1350 }
1351 next:
1352 /*
1353 * In the vma_merge() successful mprotect-like case 8:
1354 * the next vma was merged into the current one and
1355 * the current one has not been updated yet.
1356 */
1357 vma->vm_flags = new_flags;
1358 vma->vm_userfaultfd_ctx.ctx = ctx;
1359
1360 skip:
1361 prev = vma;
1362 start = vma->vm_end;
1363 vma = vma->vm_next;
1364 } while (vma && vma->vm_start < end);
1365out_unlock:
1366 up_write(&mm->mmap_sem);
Oleg Nesterovd2005e32016-05-20 16:58:36 -07001367 mmput(mm);
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001368 if (!ret) {
1369 /*
1370 * Now that we scanned all vmas we can already tell
1371 * userland which ioctls methods are guaranteed to
1372 * succeed on this range.
1373 */
Mike Rapoportcac67322017-02-22 15:43:40 -08001374 if (put_user(non_anon_pages ? UFFD_API_RANGE_IOCTLS_BASIC :
Mike Kravetzcab350a2017-02-22 15:43:04 -08001375 UFFD_API_RANGE_IOCTLS,
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001376 &user_uffdio_register->ioctls))
1377 ret = -EFAULT;
1378 }
1379out:
1380 return ret;
1381}
1382
1383static int userfaultfd_unregister(struct userfaultfd_ctx *ctx,
1384 unsigned long arg)
1385{
1386 struct mm_struct *mm = ctx->mm;
1387 struct vm_area_struct *vma, *prev, *cur;
1388 int ret;
1389 struct uffdio_range uffdio_unregister;
1390 unsigned long new_flags;
1391 bool found;
1392 unsigned long start, end, vma_end;
1393 const void __user *buf = (void __user *)arg;
1394
1395 ret = -EFAULT;
1396 if (copy_from_user(&uffdio_unregister, buf, sizeof(uffdio_unregister)))
1397 goto out;
1398
1399 ret = validate_range(mm, uffdio_unregister.start,
1400 uffdio_unregister.len);
1401 if (ret)
1402 goto out;
1403
1404 start = uffdio_unregister.start;
1405 end = start + uffdio_unregister.len;
1406
Oleg Nesterovd2005e32016-05-20 16:58:36 -07001407 ret = -ENOMEM;
1408 if (!mmget_not_zero(mm))
1409 goto out;
1410
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001411 down_write(&mm->mmap_sem);
1412 vma = find_vma_prev(mm, start, &prev);
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001413 if (!vma)
1414 goto out_unlock;
1415
1416 /* check that there's at least one vma in the range */
1417 ret = -EINVAL;
1418 if (vma->vm_start >= end)
1419 goto out_unlock;
1420
1421 /*
Mike Kravetzcab350a2017-02-22 15:43:04 -08001422 * If the first vma contains huge pages, make sure start address
1423 * is aligned to huge page size.
1424 */
1425 if (is_vm_hugetlb_page(vma)) {
1426 unsigned long vma_hpagesize = vma_kernel_pagesize(vma);
1427
1428 if (start & (vma_hpagesize - 1))
1429 goto out_unlock;
1430 }
1431
1432 /*
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001433 * Search for not compatible vmas.
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001434 */
1435 found = false;
1436 ret = -EINVAL;
1437 for (cur = vma; cur && cur->vm_start < end; cur = cur->vm_next) {
1438 cond_resched();
1439
1440 BUG_ON(!!cur->vm_userfaultfd_ctx.ctx ^
1441 !!(cur->vm_flags & (VM_UFFD_MISSING | VM_UFFD_WP)));
1442
1443 /*
1444 * Check not compatible vmas, not strictly required
1445 * here as not compatible vmas cannot have an
1446 * userfaultfd_ctx registered on them, but this
1447 * provides for more strict behavior to notice
1448 * unregistration errors.
1449 */
Mike Rapoportba6907d2017-02-22 15:43:22 -08001450 if (!vma_can_userfault(cur))
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001451 goto out_unlock;
1452
1453 found = true;
1454 }
1455 BUG_ON(!found);
1456
1457 if (vma->vm_start < start)
1458 prev = vma;
1459
1460 ret = 0;
1461 do {
1462 cond_resched();
1463
Mike Rapoportba6907d2017-02-22 15:43:22 -08001464 BUG_ON(!vma_can_userfault(vma));
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001465
1466 /*
1467 * Nothing to do: this vma is already registered into this
1468 * userfaultfd and with the right tracking mode too.
1469 */
1470 if (!vma->vm_userfaultfd_ctx.ctx)
1471 goto skip;
1472
1473 if (vma->vm_start > start)
1474 start = vma->vm_start;
1475 vma_end = min(end, vma->vm_end);
1476
Andrea Arcangeli09fa5292017-02-22 15:42:46 -08001477 if (userfaultfd_missing(vma)) {
1478 /*
1479 * Wake any concurrent pending userfault while
1480 * we unregister, so they will not hang
1481 * permanently and it avoids userland to call
1482 * UFFDIO_WAKE explicitly.
1483 */
1484 struct userfaultfd_wake_range range;
1485 range.start = start;
1486 range.len = vma_end - start;
1487 wake_userfault(vma->vm_userfaultfd_ctx.ctx, &range);
1488 }
1489
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001490 new_flags = vma->vm_flags & ~(VM_UFFD_MISSING | VM_UFFD_WP);
1491 prev = vma_merge(mm, prev, start, vma_end, new_flags,
1492 vma->anon_vma, vma->vm_file, vma->vm_pgoff,
1493 vma_policy(vma),
1494 NULL_VM_UFFD_CTX);
1495 if (prev) {
1496 vma = prev;
1497 goto next;
1498 }
1499 if (vma->vm_start < start) {
1500 ret = split_vma(mm, vma, start, 1);
1501 if (ret)
1502 break;
1503 }
1504 if (vma->vm_end > end) {
1505 ret = split_vma(mm, vma, end, 0);
1506 if (ret)
1507 break;
1508 }
1509 next:
1510 /*
1511 * In the vma_merge() successful mprotect-like case 8:
1512 * the next vma was merged into the current one and
1513 * the current one has not been updated yet.
1514 */
1515 vma->vm_flags = new_flags;
1516 vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX;
1517
1518 skip:
1519 prev = vma;
1520 start = vma->vm_end;
1521 vma = vma->vm_next;
1522 } while (vma && vma->vm_start < end);
1523out_unlock:
1524 up_write(&mm->mmap_sem);
Oleg Nesterovd2005e32016-05-20 16:58:36 -07001525 mmput(mm);
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001526out:
1527 return ret;
1528}
1529
1530/*
Andrea Arcangeliba85c702015-09-04 15:46:41 -07001531 * userfaultfd_wake may be used in combination with the
1532 * UFFDIO_*_MODE_DONTWAKE to wakeup userfaults in batches.
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001533 */
1534static int userfaultfd_wake(struct userfaultfd_ctx *ctx,
1535 unsigned long arg)
1536{
1537 int ret;
1538 struct uffdio_range uffdio_wake;
1539 struct userfaultfd_wake_range range;
1540 const void __user *buf = (void __user *)arg;
1541
1542 ret = -EFAULT;
1543 if (copy_from_user(&uffdio_wake, buf, sizeof(uffdio_wake)))
1544 goto out;
1545
1546 ret = validate_range(ctx->mm, uffdio_wake.start, uffdio_wake.len);
1547 if (ret)
1548 goto out;
1549
1550 range.start = uffdio_wake.start;
1551 range.len = uffdio_wake.len;
1552
1553 /*
1554 * len == 0 means wake all and we don't want to wake all here,
1555 * so check it again to be sure.
1556 */
1557 VM_BUG_ON(!range.len);
1558
1559 wake_userfault(ctx, &range);
1560 ret = 0;
1561
1562out:
1563 return ret;
1564}
1565
Andrea Arcangeliad465ca2015-09-04 15:47:11 -07001566static int userfaultfd_copy(struct userfaultfd_ctx *ctx,
1567 unsigned long arg)
1568{
1569 __s64 ret;
1570 struct uffdio_copy uffdio_copy;
1571 struct uffdio_copy __user *user_uffdio_copy;
1572 struct userfaultfd_wake_range range;
1573
1574 user_uffdio_copy = (struct uffdio_copy __user *) arg;
1575
1576 ret = -EFAULT;
1577 if (copy_from_user(&uffdio_copy, user_uffdio_copy,
1578 /* don't copy "copy" last field */
1579 sizeof(uffdio_copy)-sizeof(__s64)))
1580 goto out;
1581
1582 ret = validate_range(ctx->mm, uffdio_copy.dst, uffdio_copy.len);
1583 if (ret)
1584 goto out;
1585 /*
1586 * double check for wraparound just in case. copy_from_user()
1587 * will later check uffdio_copy.src + uffdio_copy.len to fit
1588 * in the userland range.
1589 */
1590 ret = -EINVAL;
1591 if (uffdio_copy.src + uffdio_copy.len <= uffdio_copy.src)
1592 goto out;
1593 if (uffdio_copy.mode & ~UFFDIO_COPY_MODE_DONTWAKE)
1594 goto out;
Oleg Nesterovd2005e32016-05-20 16:58:36 -07001595 if (mmget_not_zero(ctx->mm)) {
1596 ret = mcopy_atomic(ctx->mm, uffdio_copy.dst, uffdio_copy.src,
1597 uffdio_copy.len);
1598 mmput(ctx->mm);
Mike Rapoport96333182017-02-24 14:58:31 -08001599 } else {
1600 return -ENOSPC;
Oleg Nesterovd2005e32016-05-20 16:58:36 -07001601 }
Andrea Arcangeliad465ca2015-09-04 15:47:11 -07001602 if (unlikely(put_user(ret, &user_uffdio_copy->copy)))
1603 return -EFAULT;
1604 if (ret < 0)
1605 goto out;
1606 BUG_ON(!ret);
1607 /* len == 0 would wake all */
1608 range.len = ret;
1609 if (!(uffdio_copy.mode & UFFDIO_COPY_MODE_DONTWAKE)) {
1610 range.start = uffdio_copy.dst;
1611 wake_userfault(ctx, &range);
1612 }
1613 ret = range.len == uffdio_copy.len ? 0 : -EAGAIN;
1614out:
1615 return ret;
1616}
1617
1618static int userfaultfd_zeropage(struct userfaultfd_ctx *ctx,
1619 unsigned long arg)
1620{
1621 __s64 ret;
1622 struct uffdio_zeropage uffdio_zeropage;
1623 struct uffdio_zeropage __user *user_uffdio_zeropage;
1624 struct userfaultfd_wake_range range;
1625
1626 user_uffdio_zeropage = (struct uffdio_zeropage __user *) arg;
1627
1628 ret = -EFAULT;
1629 if (copy_from_user(&uffdio_zeropage, user_uffdio_zeropage,
1630 /* don't copy "zeropage" last field */
1631 sizeof(uffdio_zeropage)-sizeof(__s64)))
1632 goto out;
1633
1634 ret = validate_range(ctx->mm, uffdio_zeropage.range.start,
1635 uffdio_zeropage.range.len);
1636 if (ret)
1637 goto out;
1638 ret = -EINVAL;
1639 if (uffdio_zeropage.mode & ~UFFDIO_ZEROPAGE_MODE_DONTWAKE)
1640 goto out;
1641
Oleg Nesterovd2005e32016-05-20 16:58:36 -07001642 if (mmget_not_zero(ctx->mm)) {
1643 ret = mfill_zeropage(ctx->mm, uffdio_zeropage.range.start,
1644 uffdio_zeropage.range.len);
1645 mmput(ctx->mm);
1646 }
Andrea Arcangeliad465ca2015-09-04 15:47:11 -07001647 if (unlikely(put_user(ret, &user_uffdio_zeropage->zeropage)))
1648 return -EFAULT;
1649 if (ret < 0)
1650 goto out;
1651 /* len == 0 would wake all */
1652 BUG_ON(!ret);
1653 range.len = ret;
1654 if (!(uffdio_zeropage.mode & UFFDIO_ZEROPAGE_MODE_DONTWAKE)) {
1655 range.start = uffdio_zeropage.range.start;
1656 wake_userfault(ctx, &range);
1657 }
1658 ret = range.len == uffdio_zeropage.range.len ? 0 : -EAGAIN;
1659out:
1660 return ret;
1661}
1662
Pavel Emelyanov9cd75c32017-02-22 15:42:21 -08001663static inline unsigned int uffd_ctx_features(__u64 user_features)
1664{
1665 /*
1666 * For the current set of features the bits just coincide
1667 */
1668 return (unsigned int)user_features;
1669}
1670
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001671/*
1672 * userland asks for a certain API version and we return which bits
1673 * and ioctl commands are implemented in this kernel for such API
1674 * version or -EINVAL if unknown.
1675 */
1676static int userfaultfd_api(struct userfaultfd_ctx *ctx,
1677 unsigned long arg)
1678{
1679 struct uffdio_api uffdio_api;
1680 void __user *buf = (void __user *)arg;
1681 int ret;
Andrea Arcangeli65603142017-02-22 15:42:24 -08001682 __u64 features;
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001683
1684 ret = -EINVAL;
1685 if (ctx->state != UFFD_STATE_WAIT_API)
1686 goto out;
1687 ret = -EFAULT;
Andrea Arcangelia9b85f92015-09-04 15:46:37 -07001688 if (copy_from_user(&uffdio_api, buf, sizeof(uffdio_api)))
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001689 goto out;
Andrea Arcangeli65603142017-02-22 15:42:24 -08001690 features = uffdio_api.features;
1691 if (uffdio_api.api != UFFD_API || (features & ~UFFD_API_FEATURES)) {
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001692 memset(&uffdio_api, 0, sizeof(uffdio_api));
1693 if (copy_to_user(buf, &uffdio_api, sizeof(uffdio_api)))
1694 goto out;
1695 ret = -EINVAL;
1696 goto out;
1697 }
Andrea Arcangeli65603142017-02-22 15:42:24 -08001698 /* report all available features and ioctls to userland */
1699 uffdio_api.features = UFFD_API_FEATURES;
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001700 uffdio_api.ioctls = UFFD_API_IOCTLS;
1701 ret = -EFAULT;
1702 if (copy_to_user(buf, &uffdio_api, sizeof(uffdio_api)))
1703 goto out;
1704 ctx->state = UFFD_STATE_RUNNING;
Andrea Arcangeli65603142017-02-22 15:42:24 -08001705 /* only enable the requested features for this uffd context */
1706 ctx->features = uffd_ctx_features(features);
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001707 ret = 0;
1708out:
1709 return ret;
1710}
1711
1712static long userfaultfd_ioctl(struct file *file, unsigned cmd,
1713 unsigned long arg)
1714{
1715 int ret = -EINVAL;
1716 struct userfaultfd_ctx *ctx = file->private_data;
1717
Andrea Arcangelie6485a42015-09-04 15:47:15 -07001718 if (cmd != UFFDIO_API && ctx->state == UFFD_STATE_WAIT_API)
1719 return -EINVAL;
1720
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001721 switch(cmd) {
1722 case UFFDIO_API:
1723 ret = userfaultfd_api(ctx, arg);
1724 break;
1725 case UFFDIO_REGISTER:
1726 ret = userfaultfd_register(ctx, arg);
1727 break;
1728 case UFFDIO_UNREGISTER:
1729 ret = userfaultfd_unregister(ctx, arg);
1730 break;
1731 case UFFDIO_WAKE:
1732 ret = userfaultfd_wake(ctx, arg);
1733 break;
Andrea Arcangeliad465ca2015-09-04 15:47:11 -07001734 case UFFDIO_COPY:
1735 ret = userfaultfd_copy(ctx, arg);
1736 break;
1737 case UFFDIO_ZEROPAGE:
1738 ret = userfaultfd_zeropage(ctx, arg);
1739 break;
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001740 }
1741 return ret;
1742}
1743
1744#ifdef CONFIG_PROC_FS
1745static void userfaultfd_show_fdinfo(struct seq_file *m, struct file *f)
1746{
1747 struct userfaultfd_ctx *ctx = f->private_data;
Ingo Molnarac6424b2017-06-20 12:06:13 +02001748 wait_queue_entry_t *wq;
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001749 struct userfaultfd_wait_queue *uwq;
1750 unsigned long pending = 0, total = 0;
1751
Andrea Arcangeli15b726e2015-09-04 15:46:44 -07001752 spin_lock(&ctx->fault_pending_wqh.lock);
Ingo Molnar2055da92017-06-20 12:06:46 +02001753 list_for_each_entry(wq, &ctx->fault_pending_wqh.head, entry) {
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001754 uwq = container_of(wq, struct userfaultfd_wait_queue, wq);
Andrea Arcangeli15b726e2015-09-04 15:46:44 -07001755 pending++;
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001756 total++;
1757 }
Ingo Molnar2055da92017-06-20 12:06:46 +02001758 list_for_each_entry(wq, &ctx->fault_wqh.head, entry) {
Andrea Arcangeli15b726e2015-09-04 15:46:44 -07001759 uwq = container_of(wq, struct userfaultfd_wait_queue, wq);
1760 total++;
1761 }
1762 spin_unlock(&ctx->fault_pending_wqh.lock);
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001763
1764 /*
1765 * If more protocols will be added, there will be all shown
1766 * separated by a space. Like this:
1767 * protocols: aa:... bb:...
1768 */
1769 seq_printf(m, "pending:\t%lu\ntotal:\t%lu\nAPI:\t%Lx:%x:%Lx\n",
Mike Rapoport045098e2017-04-07 16:04:42 -07001770 pending, total, UFFD_API, ctx->features,
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001771 UFFD_API_IOCTLS|UFFD_API_RANGE_IOCTLS);
1772}
1773#endif
1774
1775static const struct file_operations userfaultfd_fops = {
1776#ifdef CONFIG_PROC_FS
1777 .show_fdinfo = userfaultfd_show_fdinfo,
1778#endif
1779 .release = userfaultfd_release,
1780 .poll = userfaultfd_poll,
1781 .read = userfaultfd_read,
1782 .unlocked_ioctl = userfaultfd_ioctl,
1783 .compat_ioctl = userfaultfd_ioctl,
1784 .llseek = noop_llseek,
1785};
1786
Andrea Arcangeli3004ec92015-09-04 15:46:48 -07001787static void init_once_userfaultfd_ctx(void *mem)
1788{
1789 struct userfaultfd_ctx *ctx = (struct userfaultfd_ctx *) mem;
1790
1791 init_waitqueue_head(&ctx->fault_pending_wqh);
1792 init_waitqueue_head(&ctx->fault_wqh);
Pavel Emelyanov9cd75c32017-02-22 15:42:21 -08001793 init_waitqueue_head(&ctx->event_wqh);
Andrea Arcangeli3004ec92015-09-04 15:46:48 -07001794 init_waitqueue_head(&ctx->fd_wqh);
Andrea Arcangeli2c5b7e12015-09-04 15:47:23 -07001795 seqcount_init(&ctx->refile_seq);
Andrea Arcangeli3004ec92015-09-04 15:46:48 -07001796}
1797
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001798/**
Masahiro Yamada9332ef92017-02-27 14:28:47 -08001799 * userfaultfd_file_create - Creates a userfaultfd file pointer.
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001800 * @flags: Flags for the userfaultfd file.
1801 *
Masahiro Yamada9332ef92017-02-27 14:28:47 -08001802 * This function creates a userfaultfd file pointer, w/out installing
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001803 * it into the fd table. This is useful when the userfaultfd file is
1804 * used during the initialization of data structures that require
1805 * extra setup after the userfaultfd creation. So the userfaultfd
1806 * creation is split into the file pointer creation phase, and the
1807 * file descriptor installation phase. In this way races with
1808 * userspace closing the newly installed file descriptor can be
Masahiro Yamada9332ef92017-02-27 14:28:47 -08001809 * avoided. Returns a userfaultfd file pointer, or a proper error
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001810 * pointer.
1811 */
1812static struct file *userfaultfd_file_create(int flags)
1813{
1814 struct file *file;
1815 struct userfaultfd_ctx *ctx;
1816
1817 BUG_ON(!current->mm);
1818
1819 /* Check the UFFD_* constants for consistency. */
1820 BUILD_BUG_ON(UFFD_CLOEXEC != O_CLOEXEC);
1821 BUILD_BUG_ON(UFFD_NONBLOCK != O_NONBLOCK);
1822
1823 file = ERR_PTR(-EINVAL);
1824 if (flags & ~UFFD_SHARED_FCNTL_FLAGS)
1825 goto out;
1826
1827 file = ERR_PTR(-ENOMEM);
Andrea Arcangeli3004ec92015-09-04 15:46:48 -07001828 ctx = kmem_cache_alloc(userfaultfd_ctx_cachep, GFP_KERNEL);
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001829 if (!ctx)
1830 goto out;
1831
1832 atomic_set(&ctx->refcount, 1);
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001833 ctx->flags = flags;
Pavel Emelyanov9cd75c32017-02-22 15:42:21 -08001834 ctx->features = 0;
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001835 ctx->state = UFFD_STATE_WAIT_API;
1836 ctx->released = false;
1837 ctx->mm = current->mm;
1838 /* prevent the mm struct to be freed */
Vegard Nossumf1f10072017-02-27 14:30:07 -08001839 mmgrab(ctx->mm);
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001840
1841 file = anon_inode_getfile("[userfaultfd]", &userfaultfd_fops, ctx,
1842 O_RDWR | (flags & UFFD_SHARED_FCNTL_FLAGS));
Eric Biggersc03e9462015-09-17 16:01:54 -07001843 if (IS_ERR(file)) {
Oleg Nesterovd2005e32016-05-20 16:58:36 -07001844 mmdrop(ctx->mm);
Andrea Arcangeli3004ec92015-09-04 15:46:48 -07001845 kmem_cache_free(userfaultfd_ctx_cachep, ctx);
Eric Biggersc03e9462015-09-17 16:01:54 -07001846 }
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001847out:
1848 return file;
1849}
1850
1851SYSCALL_DEFINE1(userfaultfd, int, flags)
1852{
1853 int fd, error;
1854 struct file *file;
1855
1856 error = get_unused_fd_flags(flags & UFFD_SHARED_FCNTL_FLAGS);
1857 if (error < 0)
1858 return error;
1859 fd = error;
1860
1861 file = userfaultfd_file_create(flags);
1862 if (IS_ERR(file)) {
1863 error = PTR_ERR(file);
1864 goto err_put_unused_fd;
1865 }
1866 fd_install(fd, file);
1867
1868 return fd;
1869
1870err_put_unused_fd:
1871 put_unused_fd(fd);
1872
1873 return error;
1874}
Andrea Arcangeli3004ec92015-09-04 15:46:48 -07001875
1876static int __init userfaultfd_init(void)
1877{
1878 userfaultfd_ctx_cachep = kmem_cache_create("userfaultfd_ctx_cache",
1879 sizeof(struct userfaultfd_ctx),
1880 0,
1881 SLAB_HWCACHE_ALIGN|SLAB_PANIC,
1882 init_once_userfaultfd_ctx);
1883 return 0;
1884}
1885__initcall(userfaultfd_init);