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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
Mike Rapoport5a18b642017-08-02 13:32:24 -0700857 /* Flush pending events that may still wait on event_wqh */
858 wake_up_all(&ctx->event_wqh);
859
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700860 wake_up_poll(&ctx->fd_wqh, POLLHUP);
861 userfaultfd_ctx_put(ctx);
862 return 0;
863}
864
Andrea Arcangeli15b726e2015-09-04 15:46:44 -0700865/* fault_pending_wqh.lock must be hold by the caller */
Pavel Emelyanov6dcc27f2017-02-22 15:42:18 -0800866static inline struct userfaultfd_wait_queue *find_userfault_in(
867 wait_queue_head_t *wqh)
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700868{
Ingo Molnarac6424b2017-06-20 12:06:13 +0200869 wait_queue_entry_t *wq;
Andrea Arcangeli15b726e2015-09-04 15:46:44 -0700870 struct userfaultfd_wait_queue *uwq;
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700871
Pavel Emelyanov6dcc27f2017-02-22 15:42:18 -0800872 VM_BUG_ON(!spin_is_locked(&wqh->lock));
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700873
Andrea Arcangeli15b726e2015-09-04 15:46:44 -0700874 uwq = NULL;
Pavel Emelyanov6dcc27f2017-02-22 15:42:18 -0800875 if (!waitqueue_active(wqh))
Andrea Arcangeli15b726e2015-09-04 15:46:44 -0700876 goto out;
877 /* walk in reverse to provide FIFO behavior to read userfaults */
Ingo Molnar2055da92017-06-20 12:06:46 +0200878 wq = list_last_entry(&wqh->head, typeof(*wq), entry);
Andrea Arcangeli15b726e2015-09-04 15:46:44 -0700879 uwq = container_of(wq, struct userfaultfd_wait_queue, wq);
880out:
881 return uwq;
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700882}
883
Pavel Emelyanov6dcc27f2017-02-22 15:42:18 -0800884static inline struct userfaultfd_wait_queue *find_userfault(
885 struct userfaultfd_ctx *ctx)
886{
887 return find_userfault_in(&ctx->fault_pending_wqh);
888}
889
Pavel Emelyanov9cd75c32017-02-22 15:42:21 -0800890static inline struct userfaultfd_wait_queue *find_userfault_evt(
891 struct userfaultfd_ctx *ctx)
892{
893 return find_userfault_in(&ctx->event_wqh);
894}
895
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700896static unsigned int userfaultfd_poll(struct file *file, poll_table *wait)
897{
898 struct userfaultfd_ctx *ctx = file->private_data;
899 unsigned int ret;
900
901 poll_wait(file, &ctx->fd_wqh, wait);
902
903 switch (ctx->state) {
904 case UFFD_STATE_WAIT_API:
905 return POLLERR;
906 case UFFD_STATE_RUNNING:
Andrea Arcangeliba85c702015-09-04 15:46:41 -0700907 /*
908 * poll() never guarantees that read won't block.
909 * userfaults can be waken before they're read().
910 */
911 if (unlikely(!(file->f_flags & O_NONBLOCK)))
912 return POLLERR;
Andrea Arcangeli15b726e2015-09-04 15:46:44 -0700913 /*
914 * lockless access to see if there are pending faults
915 * __pollwait last action is the add_wait_queue but
916 * the spin_unlock would allow the waitqueue_active to
917 * pass above the actual list_add inside
918 * add_wait_queue critical section. So use a full
919 * memory barrier to serialize the list_add write of
920 * add_wait_queue() with the waitqueue_active read
921 * below.
922 */
923 ret = 0;
924 smp_mb();
925 if (waitqueue_active(&ctx->fault_pending_wqh))
926 ret = POLLIN;
Pavel Emelyanov9cd75c32017-02-22 15:42:21 -0800927 else if (waitqueue_active(&ctx->event_wqh))
928 ret = POLLIN;
929
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700930 return ret;
931 default:
Andrea Arcangeli84749012017-02-22 15:42:12 -0800932 WARN_ON_ONCE(1);
933 return POLLERR;
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700934 }
935}
936
Pavel Emelyanov893e26e2017-02-22 15:42:27 -0800937static const struct file_operations userfaultfd_fops;
938
939static int resolve_userfault_fork(struct userfaultfd_ctx *ctx,
940 struct userfaultfd_ctx *new,
941 struct uffd_msg *msg)
942{
943 int fd;
944 struct file *file;
945 unsigned int flags = new->flags & UFFD_SHARED_FCNTL_FLAGS;
946
947 fd = get_unused_fd_flags(flags);
948 if (fd < 0)
949 return fd;
950
951 file = anon_inode_getfile("[userfaultfd]", &userfaultfd_fops, new,
952 O_RDWR | flags);
953 if (IS_ERR(file)) {
954 put_unused_fd(fd);
955 return PTR_ERR(file);
956 }
957
958 fd_install(fd, file);
959 msg->arg.reserved.reserved1 = 0;
960 msg->arg.fork.ufd = fd;
961
962 return 0;
963}
964
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700965static ssize_t userfaultfd_ctx_read(struct userfaultfd_ctx *ctx, int no_wait,
Andrea Arcangelia9b85f92015-09-04 15:46:37 -0700966 struct uffd_msg *msg)
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700967{
968 ssize_t ret;
969 DECLARE_WAITQUEUE(wait, current);
Andrea Arcangeli15b726e2015-09-04 15:46:44 -0700970 struct userfaultfd_wait_queue *uwq;
Pavel Emelyanov893e26e2017-02-22 15:42:27 -0800971 /*
972 * Handling fork event requires sleeping operations, so
973 * we drop the event_wqh lock, then do these ops, then
974 * lock it back and wake up the waiter. While the lock is
975 * dropped the ewq may go away so we keep track of it
976 * carefully.
977 */
978 LIST_HEAD(fork_event);
979 struct userfaultfd_ctx *fork_nctx = NULL;
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700980
Andrea Arcangeli15b726e2015-09-04 15:46:44 -0700981 /* always take the fd_wqh lock before the fault_pending_wqh lock */
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700982 spin_lock(&ctx->fd_wqh.lock);
983 __add_wait_queue(&ctx->fd_wqh, &wait);
984 for (;;) {
985 set_current_state(TASK_INTERRUPTIBLE);
Andrea Arcangeli15b726e2015-09-04 15:46:44 -0700986 spin_lock(&ctx->fault_pending_wqh.lock);
987 uwq = find_userfault(ctx);
988 if (uwq) {
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700989 /*
Andrea Arcangeli2c5b7e12015-09-04 15:47:23 -0700990 * Use a seqcount to repeat the lockless check
991 * in wake_userfault() to avoid missing
992 * wakeups because during the refile both
993 * waitqueue could become empty if this is the
994 * only userfault.
995 */
996 write_seqcount_begin(&ctx->refile_seq);
997
998 /*
Andrea Arcangeli15b726e2015-09-04 15:46:44 -0700999 * The fault_pending_wqh.lock prevents the uwq
1000 * to disappear from under us.
1001 *
1002 * Refile this userfault from
1003 * fault_pending_wqh to fault_wqh, it's not
1004 * pending anymore after we read it.
1005 *
1006 * Use list_del() by hand (as
1007 * userfaultfd_wake_function also uses
1008 * list_del_init() by hand) to be sure nobody
1009 * changes __remove_wait_queue() to use
1010 * list_del_init() in turn breaking the
1011 * !list_empty_careful() check in
Ingo Molnar2055da92017-06-20 12:06:46 +02001012 * handle_userfault(). The uwq->wq.head list
Andrea Arcangeli15b726e2015-09-04 15:46:44 -07001013 * must never be empty at any time during the
1014 * refile, or the waitqueue could disappear
1015 * from under us. The "wait_queue_head_t"
1016 * parameter of __remove_wait_queue() is unused
1017 * anyway.
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001018 */
Ingo Molnar2055da92017-06-20 12:06:46 +02001019 list_del(&uwq->wq.entry);
Andrea Arcangeli15b726e2015-09-04 15:46:44 -07001020 __add_wait_queue(&ctx->fault_wqh, &uwq->wq);
1021
Andrea Arcangeli2c5b7e12015-09-04 15:47:23 -07001022 write_seqcount_end(&ctx->refile_seq);
1023
Andrea Arcangelia9b85f92015-09-04 15:46:37 -07001024 /* careful to always initialize msg if ret == 0 */
1025 *msg = uwq->msg;
Andrea Arcangeli15b726e2015-09-04 15:46:44 -07001026 spin_unlock(&ctx->fault_pending_wqh.lock);
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001027 ret = 0;
1028 break;
1029 }
Andrea Arcangeli15b726e2015-09-04 15:46:44 -07001030 spin_unlock(&ctx->fault_pending_wqh.lock);
Pavel Emelyanov9cd75c32017-02-22 15:42:21 -08001031
1032 spin_lock(&ctx->event_wqh.lock);
1033 uwq = find_userfault_evt(ctx);
1034 if (uwq) {
1035 *msg = uwq->msg;
1036
Pavel Emelyanov893e26e2017-02-22 15:42:27 -08001037 if (uwq->msg.event == UFFD_EVENT_FORK) {
1038 fork_nctx = (struct userfaultfd_ctx *)
1039 (unsigned long)
1040 uwq->msg.arg.reserved.reserved1;
Ingo Molnar2055da92017-06-20 12:06:46 +02001041 list_move(&uwq->wq.entry, &fork_event);
Pavel Emelyanov893e26e2017-02-22 15:42:27 -08001042 spin_unlock(&ctx->event_wqh.lock);
1043 ret = 0;
1044 break;
1045 }
1046
Pavel Emelyanov9cd75c32017-02-22 15:42:21 -08001047 userfaultfd_event_complete(ctx, uwq);
1048 spin_unlock(&ctx->event_wqh.lock);
1049 ret = 0;
1050 break;
1051 }
1052 spin_unlock(&ctx->event_wqh.lock);
1053
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001054 if (signal_pending(current)) {
1055 ret = -ERESTARTSYS;
1056 break;
1057 }
1058 if (no_wait) {
1059 ret = -EAGAIN;
1060 break;
1061 }
1062 spin_unlock(&ctx->fd_wqh.lock);
1063 schedule();
1064 spin_lock(&ctx->fd_wqh.lock);
1065 }
1066 __remove_wait_queue(&ctx->fd_wqh, &wait);
1067 __set_current_state(TASK_RUNNING);
1068 spin_unlock(&ctx->fd_wqh.lock);
1069
Pavel Emelyanov893e26e2017-02-22 15:42:27 -08001070 if (!ret && msg->event == UFFD_EVENT_FORK) {
1071 ret = resolve_userfault_fork(ctx, fork_nctx, msg);
1072
1073 if (!ret) {
1074 spin_lock(&ctx->event_wqh.lock);
1075 if (!list_empty(&fork_event)) {
1076 uwq = list_first_entry(&fork_event,
1077 typeof(*uwq),
Ingo Molnar2055da92017-06-20 12:06:46 +02001078 wq.entry);
1079 list_del(&uwq->wq.entry);
Pavel Emelyanov893e26e2017-02-22 15:42:27 -08001080 __add_wait_queue(&ctx->event_wqh, &uwq->wq);
1081 userfaultfd_event_complete(ctx, uwq);
1082 }
1083 spin_unlock(&ctx->event_wqh.lock);
1084 }
1085 }
1086
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001087 return ret;
1088}
1089
1090static ssize_t userfaultfd_read(struct file *file, char __user *buf,
1091 size_t count, loff_t *ppos)
1092{
1093 struct userfaultfd_ctx *ctx = file->private_data;
1094 ssize_t _ret, ret = 0;
Andrea Arcangelia9b85f92015-09-04 15:46:37 -07001095 struct uffd_msg msg;
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001096 int no_wait = file->f_flags & O_NONBLOCK;
1097
1098 if (ctx->state == UFFD_STATE_WAIT_API)
1099 return -EINVAL;
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001100
1101 for (;;) {
Andrea Arcangelia9b85f92015-09-04 15:46:37 -07001102 if (count < sizeof(msg))
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001103 return ret ? ret : -EINVAL;
Andrea Arcangelia9b85f92015-09-04 15:46:37 -07001104 _ret = userfaultfd_ctx_read(ctx, no_wait, &msg);
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001105 if (_ret < 0)
1106 return ret ? ret : _ret;
Andrea Arcangelia9b85f92015-09-04 15:46:37 -07001107 if (copy_to_user((__u64 __user *) buf, &msg, sizeof(msg)))
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001108 return ret ? ret : -EFAULT;
Andrea Arcangelia9b85f92015-09-04 15:46:37 -07001109 ret += sizeof(msg);
1110 buf += sizeof(msg);
1111 count -= sizeof(msg);
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001112 /*
1113 * Allow to read more than one fault at time but only
1114 * block if waiting for the very first one.
1115 */
1116 no_wait = O_NONBLOCK;
1117 }
1118}
1119
1120static void __wake_userfault(struct userfaultfd_ctx *ctx,
1121 struct userfaultfd_wake_range *range)
1122{
Andrea Arcangeli15b726e2015-09-04 15:46:44 -07001123 spin_lock(&ctx->fault_pending_wqh.lock);
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001124 /* wake all in the range and autoremove */
Andrea Arcangeli15b726e2015-09-04 15:46:44 -07001125 if (waitqueue_active(&ctx->fault_pending_wqh))
Andrea Arcangeliac5be6b2015-09-22 14:58:49 -07001126 __wake_up_locked_key(&ctx->fault_pending_wqh, TASK_NORMAL,
Andrea Arcangeli15b726e2015-09-04 15:46:44 -07001127 range);
1128 if (waitqueue_active(&ctx->fault_wqh))
Andrea Arcangeliac5be6b2015-09-22 14:58:49 -07001129 __wake_up_locked_key(&ctx->fault_wqh, TASK_NORMAL, range);
Andrea Arcangeli15b726e2015-09-04 15:46:44 -07001130 spin_unlock(&ctx->fault_pending_wqh.lock);
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001131}
1132
1133static __always_inline void wake_userfault(struct userfaultfd_ctx *ctx,
1134 struct userfaultfd_wake_range *range)
1135{
Andrea Arcangeli2c5b7e12015-09-04 15:47:23 -07001136 unsigned seq;
1137 bool need_wakeup;
1138
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001139 /*
1140 * To be sure waitqueue_active() is not reordered by the CPU
1141 * before the pagetable update, use an explicit SMP memory
1142 * barrier here. PT lock release or up_read(mmap_sem) still
1143 * have release semantics that can allow the
1144 * waitqueue_active() to be reordered before the pte update.
1145 */
1146 smp_mb();
1147
1148 /*
1149 * Use waitqueue_active because it's very frequent to
1150 * change the address space atomically even if there are no
1151 * userfaults yet. So we take the spinlock only when we're
1152 * sure we've userfaults to wake.
1153 */
Andrea Arcangeli2c5b7e12015-09-04 15:47:23 -07001154 do {
1155 seq = read_seqcount_begin(&ctx->refile_seq);
1156 need_wakeup = waitqueue_active(&ctx->fault_pending_wqh) ||
1157 waitqueue_active(&ctx->fault_wqh);
1158 cond_resched();
1159 } while (read_seqcount_retry(&ctx->refile_seq, seq));
1160 if (need_wakeup)
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001161 __wake_userfault(ctx, range);
1162}
1163
1164static __always_inline int validate_range(struct mm_struct *mm,
1165 __u64 start, __u64 len)
1166{
1167 __u64 task_size = mm->task_size;
1168
1169 if (start & ~PAGE_MASK)
1170 return -EINVAL;
1171 if (len & ~PAGE_MASK)
1172 return -EINVAL;
1173 if (!len)
1174 return -EINVAL;
1175 if (start < mmap_min_addr)
1176 return -EINVAL;
1177 if (start >= task_size)
1178 return -EINVAL;
1179 if (len > task_size - start)
1180 return -EINVAL;
1181 return 0;
1182}
1183
Mike Rapoportba6907d2017-02-22 15:43:22 -08001184static inline bool vma_can_userfault(struct vm_area_struct *vma)
1185{
Mike Rapoportcac67322017-02-22 15:43:40 -08001186 return vma_is_anonymous(vma) || is_vm_hugetlb_page(vma) ||
1187 vma_is_shmem(vma);
Mike Rapoportba6907d2017-02-22 15:43:22 -08001188}
1189
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001190static int userfaultfd_register(struct userfaultfd_ctx *ctx,
1191 unsigned long arg)
1192{
1193 struct mm_struct *mm = ctx->mm;
1194 struct vm_area_struct *vma, *prev, *cur;
1195 int ret;
1196 struct uffdio_register uffdio_register;
1197 struct uffdio_register __user *user_uffdio_register;
1198 unsigned long vm_flags, new_flags;
1199 bool found;
Mike Rapoportcac67322017-02-22 15:43:40 -08001200 bool non_anon_pages;
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001201 unsigned long start, end, vma_end;
1202
1203 user_uffdio_register = (struct uffdio_register __user *) arg;
1204
1205 ret = -EFAULT;
1206 if (copy_from_user(&uffdio_register, user_uffdio_register,
1207 sizeof(uffdio_register)-sizeof(__u64)))
1208 goto out;
1209
1210 ret = -EINVAL;
1211 if (!uffdio_register.mode)
1212 goto out;
1213 if (uffdio_register.mode & ~(UFFDIO_REGISTER_MODE_MISSING|
1214 UFFDIO_REGISTER_MODE_WP))
1215 goto out;
1216 vm_flags = 0;
1217 if (uffdio_register.mode & UFFDIO_REGISTER_MODE_MISSING)
1218 vm_flags |= VM_UFFD_MISSING;
1219 if (uffdio_register.mode & UFFDIO_REGISTER_MODE_WP) {
1220 vm_flags |= VM_UFFD_WP;
1221 /*
1222 * FIXME: remove the below error constraint by
1223 * implementing the wprotect tracking mode.
1224 */
1225 ret = -EINVAL;
1226 goto out;
1227 }
1228
1229 ret = validate_range(mm, uffdio_register.range.start,
1230 uffdio_register.range.len);
1231 if (ret)
1232 goto out;
1233
1234 start = uffdio_register.range.start;
1235 end = start + uffdio_register.range.len;
1236
Oleg Nesterovd2005e32016-05-20 16:58:36 -07001237 ret = -ENOMEM;
1238 if (!mmget_not_zero(mm))
1239 goto out;
1240
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001241 down_write(&mm->mmap_sem);
1242 vma = find_vma_prev(mm, start, &prev);
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001243 if (!vma)
1244 goto out_unlock;
1245
1246 /* check that there's at least one vma in the range */
1247 ret = -EINVAL;
1248 if (vma->vm_start >= end)
1249 goto out_unlock;
1250
1251 /*
Mike Kravetzcab350a2017-02-22 15:43:04 -08001252 * If the first vma contains huge pages, make sure start address
1253 * is aligned to huge page size.
1254 */
1255 if (is_vm_hugetlb_page(vma)) {
1256 unsigned long vma_hpagesize = vma_kernel_pagesize(vma);
1257
1258 if (start & (vma_hpagesize - 1))
1259 goto out_unlock;
1260 }
1261
1262 /*
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001263 * Search for not compatible vmas.
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001264 */
1265 found = false;
Mike Rapoportcac67322017-02-22 15:43:40 -08001266 non_anon_pages = false;
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001267 for (cur = vma; cur && cur->vm_start < end; cur = cur->vm_next) {
1268 cond_resched();
1269
1270 BUG_ON(!!cur->vm_userfaultfd_ctx.ctx ^
1271 !!(cur->vm_flags & (VM_UFFD_MISSING | VM_UFFD_WP)));
1272
1273 /* check not compatible vmas */
1274 ret = -EINVAL;
Mike Rapoportba6907d2017-02-22 15:43:22 -08001275 if (!vma_can_userfault(cur))
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001276 goto out_unlock;
Mike Kravetzcab350a2017-02-22 15:43:04 -08001277 /*
1278 * If this vma contains ending address, and huge pages
1279 * check alignment.
1280 */
1281 if (is_vm_hugetlb_page(cur) && end <= cur->vm_end &&
1282 end > cur->vm_start) {
1283 unsigned long vma_hpagesize = vma_kernel_pagesize(cur);
1284
1285 ret = -EINVAL;
1286
1287 if (end & (vma_hpagesize - 1))
1288 goto out_unlock;
1289 }
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001290
1291 /*
1292 * Check that this vma isn't already owned by a
1293 * different userfaultfd. We can't allow more than one
1294 * userfaultfd to own a single vma simultaneously or we
1295 * wouldn't know which one to deliver the userfaults to.
1296 */
1297 ret = -EBUSY;
1298 if (cur->vm_userfaultfd_ctx.ctx &&
1299 cur->vm_userfaultfd_ctx.ctx != ctx)
1300 goto out_unlock;
1301
Mike Kravetzcab350a2017-02-22 15:43:04 -08001302 /*
1303 * Note vmas containing huge pages
1304 */
Mike Rapoportcac67322017-02-22 15:43:40 -08001305 if (is_vm_hugetlb_page(cur) || vma_is_shmem(cur))
1306 non_anon_pages = true;
Mike Kravetzcab350a2017-02-22 15:43:04 -08001307
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001308 found = true;
1309 }
1310 BUG_ON(!found);
1311
1312 if (vma->vm_start < start)
1313 prev = vma;
1314
1315 ret = 0;
1316 do {
1317 cond_resched();
1318
Mike Rapoportba6907d2017-02-22 15:43:22 -08001319 BUG_ON(!vma_can_userfault(vma));
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001320 BUG_ON(vma->vm_userfaultfd_ctx.ctx &&
1321 vma->vm_userfaultfd_ctx.ctx != ctx);
1322
1323 /*
1324 * Nothing to do: this vma is already registered into this
1325 * userfaultfd and with the right tracking mode too.
1326 */
1327 if (vma->vm_userfaultfd_ctx.ctx == ctx &&
1328 (vma->vm_flags & vm_flags) == vm_flags)
1329 goto skip;
1330
1331 if (vma->vm_start > start)
1332 start = vma->vm_start;
1333 vma_end = min(end, vma->vm_end);
1334
1335 new_flags = (vma->vm_flags & ~vm_flags) | vm_flags;
1336 prev = vma_merge(mm, prev, start, vma_end, new_flags,
1337 vma->anon_vma, vma->vm_file, vma->vm_pgoff,
1338 vma_policy(vma),
1339 ((struct vm_userfaultfd_ctx){ ctx }));
1340 if (prev) {
1341 vma = prev;
1342 goto next;
1343 }
1344 if (vma->vm_start < start) {
1345 ret = split_vma(mm, vma, start, 1);
1346 if (ret)
1347 break;
1348 }
1349 if (vma->vm_end > end) {
1350 ret = split_vma(mm, vma, end, 0);
1351 if (ret)
1352 break;
1353 }
1354 next:
1355 /*
1356 * In the vma_merge() successful mprotect-like case 8:
1357 * the next vma was merged into the current one and
1358 * the current one has not been updated yet.
1359 */
1360 vma->vm_flags = new_flags;
1361 vma->vm_userfaultfd_ctx.ctx = ctx;
1362
1363 skip:
1364 prev = vma;
1365 start = vma->vm_end;
1366 vma = vma->vm_next;
1367 } while (vma && vma->vm_start < end);
1368out_unlock:
1369 up_write(&mm->mmap_sem);
Oleg Nesterovd2005e32016-05-20 16:58:36 -07001370 mmput(mm);
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001371 if (!ret) {
1372 /*
1373 * Now that we scanned all vmas we can already tell
1374 * userland which ioctls methods are guaranteed to
1375 * succeed on this range.
1376 */
Mike Rapoportcac67322017-02-22 15:43:40 -08001377 if (put_user(non_anon_pages ? UFFD_API_RANGE_IOCTLS_BASIC :
Mike Kravetzcab350a2017-02-22 15:43:04 -08001378 UFFD_API_RANGE_IOCTLS,
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001379 &user_uffdio_register->ioctls))
1380 ret = -EFAULT;
1381 }
1382out:
1383 return ret;
1384}
1385
1386static int userfaultfd_unregister(struct userfaultfd_ctx *ctx,
1387 unsigned long arg)
1388{
1389 struct mm_struct *mm = ctx->mm;
1390 struct vm_area_struct *vma, *prev, *cur;
1391 int ret;
1392 struct uffdio_range uffdio_unregister;
1393 unsigned long new_flags;
1394 bool found;
1395 unsigned long start, end, vma_end;
1396 const void __user *buf = (void __user *)arg;
1397
1398 ret = -EFAULT;
1399 if (copy_from_user(&uffdio_unregister, buf, sizeof(uffdio_unregister)))
1400 goto out;
1401
1402 ret = validate_range(mm, uffdio_unregister.start,
1403 uffdio_unregister.len);
1404 if (ret)
1405 goto out;
1406
1407 start = uffdio_unregister.start;
1408 end = start + uffdio_unregister.len;
1409
Oleg Nesterovd2005e32016-05-20 16:58:36 -07001410 ret = -ENOMEM;
1411 if (!mmget_not_zero(mm))
1412 goto out;
1413
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001414 down_write(&mm->mmap_sem);
1415 vma = find_vma_prev(mm, start, &prev);
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001416 if (!vma)
1417 goto out_unlock;
1418
1419 /* check that there's at least one vma in the range */
1420 ret = -EINVAL;
1421 if (vma->vm_start >= end)
1422 goto out_unlock;
1423
1424 /*
Mike Kravetzcab350a2017-02-22 15:43:04 -08001425 * If the first vma contains huge pages, make sure start address
1426 * is aligned to huge page size.
1427 */
1428 if (is_vm_hugetlb_page(vma)) {
1429 unsigned long vma_hpagesize = vma_kernel_pagesize(vma);
1430
1431 if (start & (vma_hpagesize - 1))
1432 goto out_unlock;
1433 }
1434
1435 /*
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001436 * Search for not compatible vmas.
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001437 */
1438 found = false;
1439 ret = -EINVAL;
1440 for (cur = vma; cur && cur->vm_start < end; cur = cur->vm_next) {
1441 cond_resched();
1442
1443 BUG_ON(!!cur->vm_userfaultfd_ctx.ctx ^
1444 !!(cur->vm_flags & (VM_UFFD_MISSING | VM_UFFD_WP)));
1445
1446 /*
1447 * Check not compatible vmas, not strictly required
1448 * here as not compatible vmas cannot have an
1449 * userfaultfd_ctx registered on them, but this
1450 * provides for more strict behavior to notice
1451 * unregistration errors.
1452 */
Mike Rapoportba6907d2017-02-22 15:43:22 -08001453 if (!vma_can_userfault(cur))
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001454 goto out_unlock;
1455
1456 found = true;
1457 }
1458 BUG_ON(!found);
1459
1460 if (vma->vm_start < start)
1461 prev = vma;
1462
1463 ret = 0;
1464 do {
1465 cond_resched();
1466
Mike Rapoportba6907d2017-02-22 15:43:22 -08001467 BUG_ON(!vma_can_userfault(vma));
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001468
1469 /*
1470 * Nothing to do: this vma is already registered into this
1471 * userfaultfd and with the right tracking mode too.
1472 */
1473 if (!vma->vm_userfaultfd_ctx.ctx)
1474 goto skip;
1475
1476 if (vma->vm_start > start)
1477 start = vma->vm_start;
1478 vma_end = min(end, vma->vm_end);
1479
Andrea Arcangeli09fa5292017-02-22 15:42:46 -08001480 if (userfaultfd_missing(vma)) {
1481 /*
1482 * Wake any concurrent pending userfault while
1483 * we unregister, so they will not hang
1484 * permanently and it avoids userland to call
1485 * UFFDIO_WAKE explicitly.
1486 */
1487 struct userfaultfd_wake_range range;
1488 range.start = start;
1489 range.len = vma_end - start;
1490 wake_userfault(vma->vm_userfaultfd_ctx.ctx, &range);
1491 }
1492
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001493 new_flags = vma->vm_flags & ~(VM_UFFD_MISSING | VM_UFFD_WP);
1494 prev = vma_merge(mm, prev, start, vma_end, new_flags,
1495 vma->anon_vma, vma->vm_file, vma->vm_pgoff,
1496 vma_policy(vma),
1497 NULL_VM_UFFD_CTX);
1498 if (prev) {
1499 vma = prev;
1500 goto next;
1501 }
1502 if (vma->vm_start < start) {
1503 ret = split_vma(mm, vma, start, 1);
1504 if (ret)
1505 break;
1506 }
1507 if (vma->vm_end > end) {
1508 ret = split_vma(mm, vma, end, 0);
1509 if (ret)
1510 break;
1511 }
1512 next:
1513 /*
1514 * In the vma_merge() successful mprotect-like case 8:
1515 * the next vma was merged into the current one and
1516 * the current one has not been updated yet.
1517 */
1518 vma->vm_flags = new_flags;
1519 vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX;
1520
1521 skip:
1522 prev = vma;
1523 start = vma->vm_end;
1524 vma = vma->vm_next;
1525 } while (vma && vma->vm_start < end);
1526out_unlock:
1527 up_write(&mm->mmap_sem);
Oleg Nesterovd2005e32016-05-20 16:58:36 -07001528 mmput(mm);
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001529out:
1530 return ret;
1531}
1532
1533/*
Andrea Arcangeliba85c702015-09-04 15:46:41 -07001534 * userfaultfd_wake may be used in combination with the
1535 * UFFDIO_*_MODE_DONTWAKE to wakeup userfaults in batches.
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001536 */
1537static int userfaultfd_wake(struct userfaultfd_ctx *ctx,
1538 unsigned long arg)
1539{
1540 int ret;
1541 struct uffdio_range uffdio_wake;
1542 struct userfaultfd_wake_range range;
1543 const void __user *buf = (void __user *)arg;
1544
1545 ret = -EFAULT;
1546 if (copy_from_user(&uffdio_wake, buf, sizeof(uffdio_wake)))
1547 goto out;
1548
1549 ret = validate_range(ctx->mm, uffdio_wake.start, uffdio_wake.len);
1550 if (ret)
1551 goto out;
1552
1553 range.start = uffdio_wake.start;
1554 range.len = uffdio_wake.len;
1555
1556 /*
1557 * len == 0 means wake all and we don't want to wake all here,
1558 * so check it again to be sure.
1559 */
1560 VM_BUG_ON(!range.len);
1561
1562 wake_userfault(ctx, &range);
1563 ret = 0;
1564
1565out:
1566 return ret;
1567}
1568
Andrea Arcangeliad465ca2015-09-04 15:47:11 -07001569static int userfaultfd_copy(struct userfaultfd_ctx *ctx,
1570 unsigned long arg)
1571{
1572 __s64 ret;
1573 struct uffdio_copy uffdio_copy;
1574 struct uffdio_copy __user *user_uffdio_copy;
1575 struct userfaultfd_wake_range range;
1576
1577 user_uffdio_copy = (struct uffdio_copy __user *) arg;
1578
1579 ret = -EFAULT;
1580 if (copy_from_user(&uffdio_copy, user_uffdio_copy,
1581 /* don't copy "copy" last field */
1582 sizeof(uffdio_copy)-sizeof(__s64)))
1583 goto out;
1584
1585 ret = validate_range(ctx->mm, uffdio_copy.dst, uffdio_copy.len);
1586 if (ret)
1587 goto out;
1588 /*
1589 * double check for wraparound just in case. copy_from_user()
1590 * will later check uffdio_copy.src + uffdio_copy.len to fit
1591 * in the userland range.
1592 */
1593 ret = -EINVAL;
1594 if (uffdio_copy.src + uffdio_copy.len <= uffdio_copy.src)
1595 goto out;
1596 if (uffdio_copy.mode & ~UFFDIO_COPY_MODE_DONTWAKE)
1597 goto out;
Oleg Nesterovd2005e32016-05-20 16:58:36 -07001598 if (mmget_not_zero(ctx->mm)) {
1599 ret = mcopy_atomic(ctx->mm, uffdio_copy.dst, uffdio_copy.src,
1600 uffdio_copy.len);
1601 mmput(ctx->mm);
Mike Rapoport96333182017-02-24 14:58:31 -08001602 } else {
Mike Rapoporte86b2982017-08-10 15:24:32 -07001603 return -ESRCH;
Oleg Nesterovd2005e32016-05-20 16:58:36 -07001604 }
Andrea Arcangeliad465ca2015-09-04 15:47:11 -07001605 if (unlikely(put_user(ret, &user_uffdio_copy->copy)))
1606 return -EFAULT;
1607 if (ret < 0)
1608 goto out;
1609 BUG_ON(!ret);
1610 /* len == 0 would wake all */
1611 range.len = ret;
1612 if (!(uffdio_copy.mode & UFFDIO_COPY_MODE_DONTWAKE)) {
1613 range.start = uffdio_copy.dst;
1614 wake_userfault(ctx, &range);
1615 }
1616 ret = range.len == uffdio_copy.len ? 0 : -EAGAIN;
1617out:
1618 return ret;
1619}
1620
1621static int userfaultfd_zeropage(struct userfaultfd_ctx *ctx,
1622 unsigned long arg)
1623{
1624 __s64 ret;
1625 struct uffdio_zeropage uffdio_zeropage;
1626 struct uffdio_zeropage __user *user_uffdio_zeropage;
1627 struct userfaultfd_wake_range range;
1628
1629 user_uffdio_zeropage = (struct uffdio_zeropage __user *) arg;
1630
1631 ret = -EFAULT;
1632 if (copy_from_user(&uffdio_zeropage, user_uffdio_zeropage,
1633 /* don't copy "zeropage" last field */
1634 sizeof(uffdio_zeropage)-sizeof(__s64)))
1635 goto out;
1636
1637 ret = validate_range(ctx->mm, uffdio_zeropage.range.start,
1638 uffdio_zeropage.range.len);
1639 if (ret)
1640 goto out;
1641 ret = -EINVAL;
1642 if (uffdio_zeropage.mode & ~UFFDIO_ZEROPAGE_MODE_DONTWAKE)
1643 goto out;
1644
Oleg Nesterovd2005e32016-05-20 16:58:36 -07001645 if (mmget_not_zero(ctx->mm)) {
1646 ret = mfill_zeropage(ctx->mm, uffdio_zeropage.range.start,
1647 uffdio_zeropage.range.len);
1648 mmput(ctx->mm);
Mike Rapoport9d95aa42017-08-02 13:32:15 -07001649 } else {
Mike Rapoporte86b2982017-08-10 15:24:32 -07001650 return -ESRCH;
Oleg Nesterovd2005e32016-05-20 16:58:36 -07001651 }
Andrea Arcangeliad465ca2015-09-04 15:47:11 -07001652 if (unlikely(put_user(ret, &user_uffdio_zeropage->zeropage)))
1653 return -EFAULT;
1654 if (ret < 0)
1655 goto out;
1656 /* len == 0 would wake all */
1657 BUG_ON(!ret);
1658 range.len = ret;
1659 if (!(uffdio_zeropage.mode & UFFDIO_ZEROPAGE_MODE_DONTWAKE)) {
1660 range.start = uffdio_zeropage.range.start;
1661 wake_userfault(ctx, &range);
1662 }
1663 ret = range.len == uffdio_zeropage.range.len ? 0 : -EAGAIN;
1664out:
1665 return ret;
1666}
1667
Pavel Emelyanov9cd75c32017-02-22 15:42:21 -08001668static inline unsigned int uffd_ctx_features(__u64 user_features)
1669{
1670 /*
1671 * For the current set of features the bits just coincide
1672 */
1673 return (unsigned int)user_features;
1674}
1675
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001676/*
1677 * userland asks for a certain API version and we return which bits
1678 * and ioctl commands are implemented in this kernel for such API
1679 * version or -EINVAL if unknown.
1680 */
1681static int userfaultfd_api(struct userfaultfd_ctx *ctx,
1682 unsigned long arg)
1683{
1684 struct uffdio_api uffdio_api;
1685 void __user *buf = (void __user *)arg;
1686 int ret;
Andrea Arcangeli65603142017-02-22 15:42:24 -08001687 __u64 features;
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001688
1689 ret = -EINVAL;
1690 if (ctx->state != UFFD_STATE_WAIT_API)
1691 goto out;
1692 ret = -EFAULT;
Andrea Arcangelia9b85f92015-09-04 15:46:37 -07001693 if (copy_from_user(&uffdio_api, buf, sizeof(uffdio_api)))
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001694 goto out;
Andrea Arcangeli65603142017-02-22 15:42:24 -08001695 features = uffdio_api.features;
1696 if (uffdio_api.api != UFFD_API || (features & ~UFFD_API_FEATURES)) {
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001697 memset(&uffdio_api, 0, sizeof(uffdio_api));
1698 if (copy_to_user(buf, &uffdio_api, sizeof(uffdio_api)))
1699 goto out;
1700 ret = -EINVAL;
1701 goto out;
1702 }
Andrea Arcangeli65603142017-02-22 15:42:24 -08001703 /* report all available features and ioctls to userland */
1704 uffdio_api.features = UFFD_API_FEATURES;
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001705 uffdio_api.ioctls = UFFD_API_IOCTLS;
1706 ret = -EFAULT;
1707 if (copy_to_user(buf, &uffdio_api, sizeof(uffdio_api)))
1708 goto out;
1709 ctx->state = UFFD_STATE_RUNNING;
Andrea Arcangeli65603142017-02-22 15:42:24 -08001710 /* only enable the requested features for this uffd context */
1711 ctx->features = uffd_ctx_features(features);
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001712 ret = 0;
1713out:
1714 return ret;
1715}
1716
1717static long userfaultfd_ioctl(struct file *file, unsigned cmd,
1718 unsigned long arg)
1719{
1720 int ret = -EINVAL;
1721 struct userfaultfd_ctx *ctx = file->private_data;
1722
Andrea Arcangelie6485a42015-09-04 15:47:15 -07001723 if (cmd != UFFDIO_API && ctx->state == UFFD_STATE_WAIT_API)
1724 return -EINVAL;
1725
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001726 switch(cmd) {
1727 case UFFDIO_API:
1728 ret = userfaultfd_api(ctx, arg);
1729 break;
1730 case UFFDIO_REGISTER:
1731 ret = userfaultfd_register(ctx, arg);
1732 break;
1733 case UFFDIO_UNREGISTER:
1734 ret = userfaultfd_unregister(ctx, arg);
1735 break;
1736 case UFFDIO_WAKE:
1737 ret = userfaultfd_wake(ctx, arg);
1738 break;
Andrea Arcangeliad465ca2015-09-04 15:47:11 -07001739 case UFFDIO_COPY:
1740 ret = userfaultfd_copy(ctx, arg);
1741 break;
1742 case UFFDIO_ZEROPAGE:
1743 ret = userfaultfd_zeropage(ctx, arg);
1744 break;
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001745 }
1746 return ret;
1747}
1748
1749#ifdef CONFIG_PROC_FS
1750static void userfaultfd_show_fdinfo(struct seq_file *m, struct file *f)
1751{
1752 struct userfaultfd_ctx *ctx = f->private_data;
Ingo Molnarac6424b2017-06-20 12:06:13 +02001753 wait_queue_entry_t *wq;
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001754 struct userfaultfd_wait_queue *uwq;
1755 unsigned long pending = 0, total = 0;
1756
Andrea Arcangeli15b726e2015-09-04 15:46:44 -07001757 spin_lock(&ctx->fault_pending_wqh.lock);
Ingo Molnar2055da92017-06-20 12:06:46 +02001758 list_for_each_entry(wq, &ctx->fault_pending_wqh.head, entry) {
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001759 uwq = container_of(wq, struct userfaultfd_wait_queue, wq);
Andrea Arcangeli15b726e2015-09-04 15:46:44 -07001760 pending++;
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001761 total++;
1762 }
Ingo Molnar2055da92017-06-20 12:06:46 +02001763 list_for_each_entry(wq, &ctx->fault_wqh.head, entry) {
Andrea Arcangeli15b726e2015-09-04 15:46:44 -07001764 uwq = container_of(wq, struct userfaultfd_wait_queue, wq);
1765 total++;
1766 }
1767 spin_unlock(&ctx->fault_pending_wqh.lock);
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001768
1769 /*
1770 * If more protocols will be added, there will be all shown
1771 * separated by a space. Like this:
1772 * protocols: aa:... bb:...
1773 */
1774 seq_printf(m, "pending:\t%lu\ntotal:\t%lu\nAPI:\t%Lx:%x:%Lx\n",
Mike Rapoport045098e2017-04-07 16:04:42 -07001775 pending, total, UFFD_API, ctx->features,
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001776 UFFD_API_IOCTLS|UFFD_API_RANGE_IOCTLS);
1777}
1778#endif
1779
1780static const struct file_operations userfaultfd_fops = {
1781#ifdef CONFIG_PROC_FS
1782 .show_fdinfo = userfaultfd_show_fdinfo,
1783#endif
1784 .release = userfaultfd_release,
1785 .poll = userfaultfd_poll,
1786 .read = userfaultfd_read,
1787 .unlocked_ioctl = userfaultfd_ioctl,
1788 .compat_ioctl = userfaultfd_ioctl,
1789 .llseek = noop_llseek,
1790};
1791
Andrea Arcangeli3004ec92015-09-04 15:46:48 -07001792static void init_once_userfaultfd_ctx(void *mem)
1793{
1794 struct userfaultfd_ctx *ctx = (struct userfaultfd_ctx *) mem;
1795
1796 init_waitqueue_head(&ctx->fault_pending_wqh);
1797 init_waitqueue_head(&ctx->fault_wqh);
Pavel Emelyanov9cd75c32017-02-22 15:42:21 -08001798 init_waitqueue_head(&ctx->event_wqh);
Andrea Arcangeli3004ec92015-09-04 15:46:48 -07001799 init_waitqueue_head(&ctx->fd_wqh);
Andrea Arcangeli2c5b7e12015-09-04 15:47:23 -07001800 seqcount_init(&ctx->refile_seq);
Andrea Arcangeli3004ec92015-09-04 15:46:48 -07001801}
1802
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001803/**
Masahiro Yamada9332ef92017-02-27 14:28:47 -08001804 * userfaultfd_file_create - Creates a userfaultfd file pointer.
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001805 * @flags: Flags for the userfaultfd file.
1806 *
Masahiro Yamada9332ef92017-02-27 14:28:47 -08001807 * This function creates a userfaultfd file pointer, w/out installing
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001808 * it into the fd table. This is useful when the userfaultfd file is
1809 * used during the initialization of data structures that require
1810 * extra setup after the userfaultfd creation. So the userfaultfd
1811 * creation is split into the file pointer creation phase, and the
1812 * file descriptor installation phase. In this way races with
1813 * userspace closing the newly installed file descriptor can be
Masahiro Yamada9332ef92017-02-27 14:28:47 -08001814 * avoided. Returns a userfaultfd file pointer, or a proper error
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001815 * pointer.
1816 */
1817static struct file *userfaultfd_file_create(int flags)
1818{
1819 struct file *file;
1820 struct userfaultfd_ctx *ctx;
1821
1822 BUG_ON(!current->mm);
1823
1824 /* Check the UFFD_* constants for consistency. */
1825 BUILD_BUG_ON(UFFD_CLOEXEC != O_CLOEXEC);
1826 BUILD_BUG_ON(UFFD_NONBLOCK != O_NONBLOCK);
1827
1828 file = ERR_PTR(-EINVAL);
1829 if (flags & ~UFFD_SHARED_FCNTL_FLAGS)
1830 goto out;
1831
1832 file = ERR_PTR(-ENOMEM);
Andrea Arcangeli3004ec92015-09-04 15:46:48 -07001833 ctx = kmem_cache_alloc(userfaultfd_ctx_cachep, GFP_KERNEL);
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001834 if (!ctx)
1835 goto out;
1836
1837 atomic_set(&ctx->refcount, 1);
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001838 ctx->flags = flags;
Pavel Emelyanov9cd75c32017-02-22 15:42:21 -08001839 ctx->features = 0;
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001840 ctx->state = UFFD_STATE_WAIT_API;
1841 ctx->released = false;
1842 ctx->mm = current->mm;
1843 /* prevent the mm struct to be freed */
Vegard Nossumf1f10072017-02-27 14:30:07 -08001844 mmgrab(ctx->mm);
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001845
1846 file = anon_inode_getfile("[userfaultfd]", &userfaultfd_fops, ctx,
1847 O_RDWR | (flags & UFFD_SHARED_FCNTL_FLAGS));
Eric Biggersc03e9462015-09-17 16:01:54 -07001848 if (IS_ERR(file)) {
Oleg Nesterovd2005e32016-05-20 16:58:36 -07001849 mmdrop(ctx->mm);
Andrea Arcangeli3004ec92015-09-04 15:46:48 -07001850 kmem_cache_free(userfaultfd_ctx_cachep, ctx);
Eric Biggersc03e9462015-09-17 16:01:54 -07001851 }
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001852out:
1853 return file;
1854}
1855
1856SYSCALL_DEFINE1(userfaultfd, int, flags)
1857{
1858 int fd, error;
1859 struct file *file;
1860
1861 error = get_unused_fd_flags(flags & UFFD_SHARED_FCNTL_FLAGS);
1862 if (error < 0)
1863 return error;
1864 fd = error;
1865
1866 file = userfaultfd_file_create(flags);
1867 if (IS_ERR(file)) {
1868 error = PTR_ERR(file);
1869 goto err_put_unused_fd;
1870 }
1871 fd_install(fd, file);
1872
1873 return fd;
1874
1875err_put_unused_fd:
1876 put_unused_fd(fd);
1877
1878 return error;
1879}
Andrea Arcangeli3004ec92015-09-04 15:46:48 -07001880
1881static int __init userfaultfd_init(void)
1882{
1883 userfaultfd_ctx_cachep = kmem_cache_create("userfaultfd_ctx_cache",
1884 sizeof(struct userfaultfd_ctx),
1885 0,
1886 SLAB_HWCACHE_ALIGN|SLAB_PANIC,
1887 init_once_userfaultfd_ctx);
1888 return 0;
1889}
1890__initcall(userfaultfd_init);