Commit | Line | Data |
---|---|---|
86039bd3 AA |
1 | /* |
2 | * fs/userfaultfd.c | |
3 | * | |
4 | * Copyright (C) 2007 Davide Libenzi <davidel@xmailserver.org> | |
5 | * Copyright (C) 2008-2009 Red Hat, Inc. | |
6 | * Copyright (C) 2015 Red Hat, Inc. | |
7 | * | |
8 | * This work is licensed under the terms of the GNU GPL, version 2. See | |
9 | * the COPYING file in the top-level directory. | |
10 | * | |
11 | * Some part derived from fs/eventfd.c (anon inode setup) and | |
12 | * mm/ksm.c (mm hashing). | |
13 | */ | |
14 | ||
9cd75c3c | 15 | #include <linux/list.h> |
86039bd3 | 16 | #include <linux/hashtable.h> |
174cd4b1 | 17 | #include <linux/sched/signal.h> |
6e84f315 | 18 | #include <linux/sched/mm.h> |
86039bd3 AA |
19 | #include <linux/mm.h> |
20 | #include <linux/poll.h> | |
21 | #include <linux/slab.h> | |
22 | #include <linux/seq_file.h> | |
23 | #include <linux/file.h> | |
24 | #include <linux/bug.h> | |
25 | #include <linux/anon_inodes.h> | |
26 | #include <linux/syscalls.h> | |
27 | #include <linux/userfaultfd_k.h> | |
28 | #include <linux/mempolicy.h> | |
29 | #include <linux/ioctl.h> | |
30 | #include <linux/security.h> | |
cab350af | 31 | #include <linux/hugetlb.h> |
86039bd3 | 32 | |
3004ec9c AA |
33 | static struct kmem_cache *userfaultfd_ctx_cachep __read_mostly; |
34 | ||
86039bd3 AA |
35 | enum userfaultfd_state { |
36 | UFFD_STATE_WAIT_API, | |
37 | UFFD_STATE_RUNNING, | |
38 | }; | |
39 | ||
3004ec9c AA |
40 | /* |
41 | * Start with fault_pending_wqh and fault_wqh so they're more likely | |
42 | * to be in the same cacheline. | |
43 | */ | |
86039bd3 | 44 | struct userfaultfd_ctx { |
15b726ef AA |
45 | /* waitqueue head for the pending (i.e. not read) userfaults */ |
46 | wait_queue_head_t fault_pending_wqh; | |
47 | /* waitqueue head for the userfaults */ | |
86039bd3 AA |
48 | wait_queue_head_t fault_wqh; |
49 | /* waitqueue head for the pseudo fd to wakeup poll/read */ | |
50 | wait_queue_head_t fd_wqh; | |
9cd75c3c PE |
51 | /* waitqueue head for events */ |
52 | wait_queue_head_t event_wqh; | |
2c5b7e1b AA |
53 | /* a refile sequence protected by fault_pending_wqh lock */ |
54 | struct seqcount refile_seq; | |
3004ec9c | 55 | /* pseudo fd refcounting */ |
ca880420 | 56 | refcount_t refcount; |
86039bd3 AA |
57 | /* userfaultfd syscall flags */ |
58 | unsigned int flags; | |
9cd75c3c PE |
59 | /* features requested from the userspace */ |
60 | unsigned int features; | |
86039bd3 AA |
61 | /* state machine */ |
62 | enum userfaultfd_state state; | |
63 | /* released */ | |
64 | bool released; | |
df2cc96e MR |
65 | /* memory mappings are changing because of non-cooperative event */ |
66 | bool mmap_changing; | |
86039bd3 AA |
67 | /* mm with one ore more vmas attached to this userfaultfd_ctx */ |
68 | struct mm_struct *mm; | |
69 | }; | |
70 | ||
893e26e6 PE |
71 | struct userfaultfd_fork_ctx { |
72 | struct userfaultfd_ctx *orig; | |
73 | struct userfaultfd_ctx *new; | |
74 | struct list_head list; | |
75 | }; | |
76 | ||
897ab3e0 MR |
77 | struct userfaultfd_unmap_ctx { |
78 | struct userfaultfd_ctx *ctx; | |
79 | unsigned long start; | |
80 | unsigned long end; | |
81 | struct list_head list; | |
82 | }; | |
83 | ||
86039bd3 | 84 | struct userfaultfd_wait_queue { |
a9b85f94 | 85 | struct uffd_msg msg; |
ac6424b9 | 86 | wait_queue_entry_t wq; |
86039bd3 | 87 | struct userfaultfd_ctx *ctx; |
15a77c6f | 88 | bool waken; |
86039bd3 AA |
89 | }; |
90 | ||
91 | struct userfaultfd_wake_range { | |
92 | unsigned long start; | |
93 | unsigned long len; | |
94 | }; | |
95 | ||
ac6424b9 | 96 | static int userfaultfd_wake_function(wait_queue_entry_t *wq, unsigned mode, |
86039bd3 AA |
97 | int wake_flags, void *key) |
98 | { | |
99 | struct userfaultfd_wake_range *range = key; | |
100 | int ret; | |
101 | struct userfaultfd_wait_queue *uwq; | |
102 | unsigned long start, len; | |
103 | ||
104 | uwq = container_of(wq, struct userfaultfd_wait_queue, wq); | |
105 | ret = 0; | |
86039bd3 AA |
106 | /* len == 0 means wake all */ |
107 | start = range->start; | |
108 | len = range->len; | |
a9b85f94 AA |
109 | if (len && (start > uwq->msg.arg.pagefault.address || |
110 | start + len <= uwq->msg.arg.pagefault.address)) | |
86039bd3 | 111 | goto out; |
15a77c6f AA |
112 | WRITE_ONCE(uwq->waken, true); |
113 | /* | |
a9668cd6 PZ |
114 | * The Program-Order guarantees provided by the scheduler |
115 | * ensure uwq->waken is visible before the task is woken. | |
15a77c6f | 116 | */ |
86039bd3 | 117 | ret = wake_up_state(wq->private, mode); |
a9668cd6 | 118 | if (ret) { |
86039bd3 AA |
119 | /* |
120 | * Wake only once, autoremove behavior. | |
121 | * | |
a9668cd6 PZ |
122 | * After the effect of list_del_init is visible to the other |
123 | * CPUs, the waitqueue may disappear from under us, see the | |
124 | * !list_empty_careful() in handle_userfault(). | |
125 | * | |
126 | * try_to_wake_up() has an implicit smp_mb(), and the | |
127 | * wq->private is read before calling the extern function | |
128 | * "wake_up_state" (which in turns calls try_to_wake_up). | |
86039bd3 | 129 | */ |
2055da97 | 130 | list_del_init(&wq->entry); |
a9668cd6 | 131 | } |
86039bd3 AA |
132 | out: |
133 | return ret; | |
134 | } | |
135 | ||
136 | /** | |
137 | * userfaultfd_ctx_get - Acquires a reference to the internal userfaultfd | |
138 | * context. | |
139 | * @ctx: [in] Pointer to the userfaultfd context. | |
86039bd3 AA |
140 | */ |
141 | static void userfaultfd_ctx_get(struct userfaultfd_ctx *ctx) | |
142 | { | |
ca880420 | 143 | refcount_inc(&ctx->refcount); |
86039bd3 AA |
144 | } |
145 | ||
146 | /** | |
147 | * userfaultfd_ctx_put - Releases a reference to the internal userfaultfd | |
148 | * context. | |
149 | * @ctx: [in] Pointer to userfaultfd context. | |
150 | * | |
151 | * The userfaultfd context reference must have been previously acquired either | |
152 | * with userfaultfd_ctx_get() or userfaultfd_ctx_fdget(). | |
153 | */ | |
154 | static void userfaultfd_ctx_put(struct userfaultfd_ctx *ctx) | |
155 | { | |
ca880420 | 156 | if (refcount_dec_and_test(&ctx->refcount)) { |
86039bd3 AA |
157 | VM_BUG_ON(spin_is_locked(&ctx->fault_pending_wqh.lock)); |
158 | VM_BUG_ON(waitqueue_active(&ctx->fault_pending_wqh)); | |
159 | VM_BUG_ON(spin_is_locked(&ctx->fault_wqh.lock)); | |
160 | VM_BUG_ON(waitqueue_active(&ctx->fault_wqh)); | |
9cd75c3c PE |
161 | VM_BUG_ON(spin_is_locked(&ctx->event_wqh.lock)); |
162 | VM_BUG_ON(waitqueue_active(&ctx->event_wqh)); | |
86039bd3 AA |
163 | VM_BUG_ON(spin_is_locked(&ctx->fd_wqh.lock)); |
164 | VM_BUG_ON(waitqueue_active(&ctx->fd_wqh)); | |
d2005e3f | 165 | mmdrop(ctx->mm); |
3004ec9c | 166 | kmem_cache_free(userfaultfd_ctx_cachep, ctx); |
86039bd3 AA |
167 | } |
168 | } | |
169 | ||
a9b85f94 | 170 | static inline void msg_init(struct uffd_msg *msg) |
86039bd3 | 171 | { |
a9b85f94 AA |
172 | BUILD_BUG_ON(sizeof(struct uffd_msg) != 32); |
173 | /* | |
174 | * Must use memset to zero out the paddings or kernel data is | |
175 | * leaked to userland. | |
176 | */ | |
177 | memset(msg, 0, sizeof(struct uffd_msg)); | |
178 | } | |
179 | ||
180 | static inline struct uffd_msg userfault_msg(unsigned long address, | |
181 | unsigned int flags, | |
9d4ac934 AP |
182 | unsigned long reason, |
183 | unsigned int features) | |
a9b85f94 AA |
184 | { |
185 | struct uffd_msg msg; | |
186 | msg_init(&msg); | |
187 | msg.event = UFFD_EVENT_PAGEFAULT; | |
188 | msg.arg.pagefault.address = address; | |
86039bd3 AA |
189 | if (flags & FAULT_FLAG_WRITE) |
190 | /* | |
a4605a61 | 191 | * If UFFD_FEATURE_PAGEFAULT_FLAG_WP was set in the |
a9b85f94 AA |
192 | * uffdio_api.features and UFFD_PAGEFAULT_FLAG_WRITE |
193 | * was not set in a UFFD_EVENT_PAGEFAULT, it means it | |
194 | * was a read fault, otherwise if set it means it's | |
195 | * a write fault. | |
86039bd3 | 196 | */ |
a9b85f94 | 197 | msg.arg.pagefault.flags |= UFFD_PAGEFAULT_FLAG_WRITE; |
86039bd3 AA |
198 | if (reason & VM_UFFD_WP) |
199 | /* | |
a9b85f94 AA |
200 | * If UFFD_FEATURE_PAGEFAULT_FLAG_WP was set in the |
201 | * uffdio_api.features and UFFD_PAGEFAULT_FLAG_WP was | |
202 | * not set in a UFFD_EVENT_PAGEFAULT, it means it was | |
203 | * a missing fault, otherwise if set it means it's a | |
204 | * write protect fault. | |
86039bd3 | 205 | */ |
a9b85f94 | 206 | msg.arg.pagefault.flags |= UFFD_PAGEFAULT_FLAG_WP; |
9d4ac934 | 207 | if (features & UFFD_FEATURE_THREAD_ID) |
a36985d3 | 208 | msg.arg.pagefault.feat.ptid = task_pid_vnr(current); |
a9b85f94 | 209 | return msg; |
86039bd3 AA |
210 | } |
211 | ||
369cd212 MK |
212 | #ifdef CONFIG_HUGETLB_PAGE |
213 | /* | |
214 | * Same functionality as userfaultfd_must_wait below with modifications for | |
215 | * hugepmd ranges. | |
216 | */ | |
217 | static inline bool userfaultfd_huge_must_wait(struct userfaultfd_ctx *ctx, | |
7868a208 | 218 | struct vm_area_struct *vma, |
369cd212 MK |
219 | unsigned long address, |
220 | unsigned long flags, | |
221 | unsigned long reason) | |
222 | { | |
223 | struct mm_struct *mm = ctx->mm; | |
1e2c0436 | 224 | pte_t *ptep, pte; |
369cd212 MK |
225 | bool ret = true; |
226 | ||
227 | VM_BUG_ON(!rwsem_is_locked(&mm->mmap_sem)); | |
228 | ||
1e2c0436 JF |
229 | ptep = huge_pte_offset(mm, address, vma_mmu_pagesize(vma)); |
230 | ||
231 | if (!ptep) | |
369cd212 MK |
232 | goto out; |
233 | ||
234 | ret = false; | |
1e2c0436 | 235 | pte = huge_ptep_get(ptep); |
369cd212 MK |
236 | |
237 | /* | |
238 | * Lockless access: we're in a wait_event so it's ok if it | |
239 | * changes under us. | |
240 | */ | |
1e2c0436 | 241 | if (huge_pte_none(pte)) |
369cd212 | 242 | ret = true; |
1e2c0436 | 243 | if (!huge_pte_write(pte) && (reason & VM_UFFD_WP)) |
369cd212 MK |
244 | ret = true; |
245 | out: | |
246 | return ret; | |
247 | } | |
248 | #else | |
249 | static inline bool userfaultfd_huge_must_wait(struct userfaultfd_ctx *ctx, | |
7868a208 | 250 | struct vm_area_struct *vma, |
369cd212 MK |
251 | unsigned long address, |
252 | unsigned long flags, | |
253 | unsigned long reason) | |
254 | { | |
255 | return false; /* should never get here */ | |
256 | } | |
257 | #endif /* CONFIG_HUGETLB_PAGE */ | |
258 | ||
8d2afd96 AA |
259 | /* |
260 | * Verify the pagetables are still not ok after having reigstered into | |
261 | * the fault_pending_wqh to avoid userland having to UFFDIO_WAKE any | |
262 | * userfault that has already been resolved, if userfaultfd_read and | |
263 | * UFFDIO_COPY|ZEROPAGE are being run simultaneously on two different | |
264 | * threads. | |
265 | */ | |
266 | static inline bool userfaultfd_must_wait(struct userfaultfd_ctx *ctx, | |
267 | unsigned long address, | |
268 | unsigned long flags, | |
269 | unsigned long reason) | |
270 | { | |
271 | struct mm_struct *mm = ctx->mm; | |
272 | pgd_t *pgd; | |
c2febafc | 273 | p4d_t *p4d; |
8d2afd96 AA |
274 | pud_t *pud; |
275 | pmd_t *pmd, _pmd; | |
276 | pte_t *pte; | |
277 | bool ret = true; | |
278 | ||
279 | VM_BUG_ON(!rwsem_is_locked(&mm->mmap_sem)); | |
280 | ||
281 | pgd = pgd_offset(mm, address); | |
282 | if (!pgd_present(*pgd)) | |
283 | goto out; | |
c2febafc KS |
284 | p4d = p4d_offset(pgd, address); |
285 | if (!p4d_present(*p4d)) | |
286 | goto out; | |
287 | pud = pud_offset(p4d, address); | |
8d2afd96 AA |
288 | if (!pud_present(*pud)) |
289 | goto out; | |
290 | pmd = pmd_offset(pud, address); | |
291 | /* | |
292 | * READ_ONCE must function as a barrier with narrower scope | |
293 | * and it must be equivalent to: | |
294 | * _pmd = *pmd; barrier(); | |
295 | * | |
296 | * This is to deal with the instability (as in | |
297 | * pmd_trans_unstable) of the pmd. | |
298 | */ | |
299 | _pmd = READ_ONCE(*pmd); | |
a365ac09 | 300 | if (pmd_none(_pmd)) |
8d2afd96 AA |
301 | goto out; |
302 | ||
303 | ret = false; | |
a365ac09 HY |
304 | if (!pmd_present(_pmd)) |
305 | goto out; | |
306 | ||
8d2afd96 AA |
307 | if (pmd_trans_huge(_pmd)) |
308 | goto out; | |
309 | ||
310 | /* | |
311 | * the pmd is stable (as in !pmd_trans_unstable) so we can re-read it | |
312 | * and use the standard pte_offset_map() instead of parsing _pmd. | |
313 | */ | |
314 | pte = pte_offset_map(pmd, address); | |
315 | /* | |
316 | * Lockless access: we're in a wait_event so it's ok if it | |
317 | * changes under us. | |
318 | */ | |
319 | if (pte_none(*pte)) | |
320 | ret = true; | |
321 | pte_unmap(pte); | |
322 | ||
323 | out: | |
324 | return ret; | |
325 | } | |
326 | ||
86039bd3 AA |
327 | /* |
328 | * The locking rules involved in returning VM_FAULT_RETRY depending on | |
329 | * FAULT_FLAG_ALLOW_RETRY, FAULT_FLAG_RETRY_NOWAIT and | |
330 | * FAULT_FLAG_KILLABLE are not straightforward. The "Caution" | |
331 | * recommendation in __lock_page_or_retry is not an understatement. | |
332 | * | |
333 | * If FAULT_FLAG_ALLOW_RETRY is set, the mmap_sem must be released | |
334 | * before returning VM_FAULT_RETRY only if FAULT_FLAG_RETRY_NOWAIT is | |
335 | * not set. | |
336 | * | |
337 | * If FAULT_FLAG_ALLOW_RETRY is set but FAULT_FLAG_KILLABLE is not | |
338 | * set, VM_FAULT_RETRY can still be returned if and only if there are | |
339 | * fatal_signal_pending()s, and the mmap_sem must be released before | |
340 | * returning it. | |
341 | */ | |
2b740303 | 342 | vm_fault_t handle_userfault(struct vm_fault *vmf, unsigned long reason) |
86039bd3 | 343 | { |
82b0f8c3 | 344 | struct mm_struct *mm = vmf->vma->vm_mm; |
86039bd3 AA |
345 | struct userfaultfd_ctx *ctx; |
346 | struct userfaultfd_wait_queue uwq; | |
2b740303 | 347 | vm_fault_t ret = VM_FAULT_SIGBUS; |
dfa37dc3 | 348 | bool must_wait, return_to_userland; |
15a77c6f | 349 | long blocking_state; |
86039bd3 | 350 | |
64c2b203 AA |
351 | /* |
352 | * We don't do userfault handling for the final child pid update. | |
353 | * | |
354 | * We also don't do userfault handling during | |
355 | * coredumping. hugetlbfs has the special | |
356 | * follow_hugetlb_page() to skip missing pages in the | |
357 | * FOLL_DUMP case, anon memory also checks for FOLL_DUMP with | |
358 | * the no_page_table() helper in follow_page_mask(), but the | |
359 | * shmem_vm_ops->fault method is invoked even during | |
360 | * coredumping without mmap_sem and it ends up here. | |
361 | */ | |
362 | if (current->flags & (PF_EXITING|PF_DUMPCORE)) | |
363 | goto out; | |
364 | ||
365 | /* | |
366 | * Coredumping runs without mmap_sem so we can only check that | |
367 | * the mmap_sem is held, if PF_DUMPCORE was not set. | |
368 | */ | |
369 | WARN_ON_ONCE(!rwsem_is_locked(&mm->mmap_sem)); | |
370 | ||
82b0f8c3 | 371 | ctx = vmf->vma->vm_userfaultfd_ctx.ctx; |
86039bd3 | 372 | if (!ctx) |
ba85c702 | 373 | goto out; |
86039bd3 AA |
374 | |
375 | BUG_ON(ctx->mm != mm); | |
376 | ||
377 | VM_BUG_ON(reason & ~(VM_UFFD_MISSING|VM_UFFD_WP)); | |
378 | VM_BUG_ON(!(reason & VM_UFFD_MISSING) ^ !!(reason & VM_UFFD_WP)); | |
379 | ||
2d6d6f5a PS |
380 | if (ctx->features & UFFD_FEATURE_SIGBUS) |
381 | goto out; | |
382 | ||
86039bd3 AA |
383 | /* |
384 | * If it's already released don't get it. This avoids to loop | |
385 | * in __get_user_pages if userfaultfd_release waits on the | |
386 | * caller of handle_userfault to release the mmap_sem. | |
387 | */ | |
6aa7de05 | 388 | if (unlikely(READ_ONCE(ctx->released))) { |
656710a6 AA |
389 | /* |
390 | * Don't return VM_FAULT_SIGBUS in this case, so a non | |
391 | * cooperative manager can close the uffd after the | |
392 | * last UFFDIO_COPY, without risking to trigger an | |
393 | * involuntary SIGBUS if the process was starting the | |
394 | * userfaultfd while the userfaultfd was still armed | |
395 | * (but after the last UFFDIO_COPY). If the uffd | |
396 | * wasn't already closed when the userfault reached | |
397 | * this point, that would normally be solved by | |
398 | * userfaultfd_must_wait returning 'false'. | |
399 | * | |
400 | * If we were to return VM_FAULT_SIGBUS here, the non | |
401 | * cooperative manager would be instead forced to | |
402 | * always call UFFDIO_UNREGISTER before it can safely | |
403 | * close the uffd. | |
404 | */ | |
405 | ret = VM_FAULT_NOPAGE; | |
ba85c702 | 406 | goto out; |
656710a6 | 407 | } |
86039bd3 AA |
408 | |
409 | /* | |
410 | * Check that we can return VM_FAULT_RETRY. | |
411 | * | |
412 | * NOTE: it should become possible to return VM_FAULT_RETRY | |
413 | * even if FAULT_FLAG_TRIED is set without leading to gup() | |
414 | * -EBUSY failures, if the userfaultfd is to be extended for | |
415 | * VM_UFFD_WP tracking and we intend to arm the userfault | |
416 | * without first stopping userland access to the memory. For | |
417 | * VM_UFFD_MISSING userfaults this is enough for now. | |
418 | */ | |
82b0f8c3 | 419 | if (unlikely(!(vmf->flags & FAULT_FLAG_ALLOW_RETRY))) { |
86039bd3 AA |
420 | /* |
421 | * Validate the invariant that nowait must allow retry | |
422 | * to be sure not to return SIGBUS erroneously on | |
423 | * nowait invocations. | |
424 | */ | |
82b0f8c3 | 425 | BUG_ON(vmf->flags & FAULT_FLAG_RETRY_NOWAIT); |
86039bd3 AA |
426 | #ifdef CONFIG_DEBUG_VM |
427 | if (printk_ratelimit()) { | |
428 | printk(KERN_WARNING | |
82b0f8c3 JK |
429 | "FAULT_FLAG_ALLOW_RETRY missing %x\n", |
430 | vmf->flags); | |
86039bd3 AA |
431 | dump_stack(); |
432 | } | |
433 | #endif | |
ba85c702 | 434 | goto out; |
86039bd3 AA |
435 | } |
436 | ||
437 | /* | |
438 | * Handle nowait, not much to do other than tell it to retry | |
439 | * and wait. | |
440 | */ | |
ba85c702 | 441 | ret = VM_FAULT_RETRY; |
82b0f8c3 | 442 | if (vmf->flags & FAULT_FLAG_RETRY_NOWAIT) |
ba85c702 | 443 | goto out; |
86039bd3 AA |
444 | |
445 | /* take the reference before dropping the mmap_sem */ | |
446 | userfaultfd_ctx_get(ctx); | |
447 | ||
86039bd3 AA |
448 | init_waitqueue_func_entry(&uwq.wq, userfaultfd_wake_function); |
449 | uwq.wq.private = current; | |
9d4ac934 AP |
450 | uwq.msg = userfault_msg(vmf->address, vmf->flags, reason, |
451 | ctx->features); | |
86039bd3 | 452 | uwq.ctx = ctx; |
15a77c6f | 453 | uwq.waken = false; |
86039bd3 | 454 | |
bae473a4 | 455 | return_to_userland = |
82b0f8c3 | 456 | (vmf->flags & (FAULT_FLAG_USER|FAULT_FLAG_KILLABLE)) == |
dfa37dc3 | 457 | (FAULT_FLAG_USER|FAULT_FLAG_KILLABLE); |
15a77c6f AA |
458 | blocking_state = return_to_userland ? TASK_INTERRUPTIBLE : |
459 | TASK_KILLABLE; | |
dfa37dc3 | 460 | |
15b726ef | 461 | spin_lock(&ctx->fault_pending_wqh.lock); |
86039bd3 AA |
462 | /* |
463 | * After the __add_wait_queue the uwq is visible to userland | |
464 | * through poll/read(). | |
465 | */ | |
15b726ef AA |
466 | __add_wait_queue(&ctx->fault_pending_wqh, &uwq.wq); |
467 | /* | |
468 | * The smp_mb() after __set_current_state prevents the reads | |
469 | * following the spin_unlock to happen before the list_add in | |
470 | * __add_wait_queue. | |
471 | */ | |
15a77c6f | 472 | set_current_state(blocking_state); |
15b726ef | 473 | spin_unlock(&ctx->fault_pending_wqh.lock); |
86039bd3 | 474 | |
369cd212 MK |
475 | if (!is_vm_hugetlb_page(vmf->vma)) |
476 | must_wait = userfaultfd_must_wait(ctx, vmf->address, vmf->flags, | |
477 | reason); | |
478 | else | |
7868a208 PA |
479 | must_wait = userfaultfd_huge_must_wait(ctx, vmf->vma, |
480 | vmf->address, | |
369cd212 | 481 | vmf->flags, reason); |
8d2afd96 AA |
482 | up_read(&mm->mmap_sem); |
483 | ||
6aa7de05 | 484 | if (likely(must_wait && !READ_ONCE(ctx->released) && |
dfa37dc3 AA |
485 | (return_to_userland ? !signal_pending(current) : |
486 | !fatal_signal_pending(current)))) { | |
a9a08845 | 487 | wake_up_poll(&ctx->fd_wqh, EPOLLIN); |
86039bd3 | 488 | schedule(); |
ba85c702 | 489 | ret |= VM_FAULT_MAJOR; |
15a77c6f AA |
490 | |
491 | /* | |
492 | * False wakeups can orginate even from rwsem before | |
493 | * up_read() however userfaults will wait either for a | |
494 | * targeted wakeup on the specific uwq waitqueue from | |
495 | * wake_userfault() or for signals or for uffd | |
496 | * release. | |
497 | */ | |
498 | while (!READ_ONCE(uwq.waken)) { | |
499 | /* | |
500 | * This needs the full smp_store_mb() | |
501 | * guarantee as the state write must be | |
502 | * visible to other CPUs before reading | |
503 | * uwq.waken from other CPUs. | |
504 | */ | |
505 | set_current_state(blocking_state); | |
506 | if (READ_ONCE(uwq.waken) || | |
507 | READ_ONCE(ctx->released) || | |
508 | (return_to_userland ? signal_pending(current) : | |
509 | fatal_signal_pending(current))) | |
510 | break; | |
511 | schedule(); | |
512 | } | |
ba85c702 | 513 | } |
86039bd3 | 514 | |
ba85c702 | 515 | __set_current_state(TASK_RUNNING); |
15b726ef | 516 | |
dfa37dc3 AA |
517 | if (return_to_userland) { |
518 | if (signal_pending(current) && | |
519 | !fatal_signal_pending(current)) { | |
520 | /* | |
521 | * If we got a SIGSTOP or SIGCONT and this is | |
522 | * a normal userland page fault, just let | |
523 | * userland return so the signal will be | |
524 | * handled and gdb debugging works. The page | |
525 | * fault code immediately after we return from | |
526 | * this function is going to release the | |
527 | * mmap_sem and it's not depending on it | |
528 | * (unlike gup would if we were not to return | |
529 | * VM_FAULT_RETRY). | |
530 | * | |
531 | * If a fatal signal is pending we still take | |
532 | * the streamlined VM_FAULT_RETRY failure path | |
533 | * and there's no need to retake the mmap_sem | |
534 | * in such case. | |
535 | */ | |
536 | down_read(&mm->mmap_sem); | |
6bbc4a41 | 537 | ret = VM_FAULT_NOPAGE; |
dfa37dc3 AA |
538 | } |
539 | } | |
540 | ||
15b726ef AA |
541 | /* |
542 | * Here we race with the list_del; list_add in | |
543 | * userfaultfd_ctx_read(), however because we don't ever run | |
544 | * list_del_init() to refile across the two lists, the prev | |
545 | * and next pointers will never point to self. list_add also | |
546 | * would never let any of the two pointers to point to | |
547 | * self. So list_empty_careful won't risk to see both pointers | |
548 | * pointing to self at any time during the list refile. The | |
549 | * only case where list_del_init() is called is the full | |
550 | * removal in the wake function and there we don't re-list_add | |
551 | * and it's fine not to block on the spinlock. The uwq on this | |
552 | * kernel stack can be released after the list_del_init. | |
553 | */ | |
2055da97 | 554 | if (!list_empty_careful(&uwq.wq.entry)) { |
15b726ef AA |
555 | spin_lock(&ctx->fault_pending_wqh.lock); |
556 | /* | |
557 | * No need of list_del_init(), the uwq on the stack | |
558 | * will be freed shortly anyway. | |
559 | */ | |
2055da97 | 560 | list_del(&uwq.wq.entry); |
15b726ef | 561 | spin_unlock(&ctx->fault_pending_wqh.lock); |
86039bd3 | 562 | } |
86039bd3 AA |
563 | |
564 | /* | |
565 | * ctx may go away after this if the userfault pseudo fd is | |
566 | * already released. | |
567 | */ | |
568 | userfaultfd_ctx_put(ctx); | |
569 | ||
ba85c702 AA |
570 | out: |
571 | return ret; | |
86039bd3 AA |
572 | } |
573 | ||
8c9e7bb7 AA |
574 | static void userfaultfd_event_wait_completion(struct userfaultfd_ctx *ctx, |
575 | struct userfaultfd_wait_queue *ewq) | |
9cd75c3c | 576 | { |
0cbb4b4f AA |
577 | struct userfaultfd_ctx *release_new_ctx; |
578 | ||
9a69a829 AA |
579 | if (WARN_ON_ONCE(current->flags & PF_EXITING)) |
580 | goto out; | |
9cd75c3c PE |
581 | |
582 | ewq->ctx = ctx; | |
583 | init_waitqueue_entry(&ewq->wq, current); | |
0cbb4b4f | 584 | release_new_ctx = NULL; |
9cd75c3c PE |
585 | |
586 | spin_lock(&ctx->event_wqh.lock); | |
587 | /* | |
588 | * After the __add_wait_queue the uwq is visible to userland | |
589 | * through poll/read(). | |
590 | */ | |
591 | __add_wait_queue(&ctx->event_wqh, &ewq->wq); | |
592 | for (;;) { | |
593 | set_current_state(TASK_KILLABLE); | |
594 | if (ewq->msg.event == 0) | |
595 | break; | |
6aa7de05 | 596 | if (READ_ONCE(ctx->released) || |
9cd75c3c | 597 | fatal_signal_pending(current)) { |
384632e6 AA |
598 | /* |
599 | * &ewq->wq may be queued in fork_event, but | |
600 | * __remove_wait_queue ignores the head | |
601 | * parameter. It would be a problem if it | |
602 | * didn't. | |
603 | */ | |
9cd75c3c | 604 | __remove_wait_queue(&ctx->event_wqh, &ewq->wq); |
7eb76d45 MR |
605 | if (ewq->msg.event == UFFD_EVENT_FORK) { |
606 | struct userfaultfd_ctx *new; | |
607 | ||
608 | new = (struct userfaultfd_ctx *) | |
609 | (unsigned long) | |
610 | ewq->msg.arg.reserved.reserved1; | |
0cbb4b4f | 611 | release_new_ctx = new; |
7eb76d45 | 612 | } |
9cd75c3c PE |
613 | break; |
614 | } | |
615 | ||
616 | spin_unlock(&ctx->event_wqh.lock); | |
617 | ||
a9a08845 | 618 | wake_up_poll(&ctx->fd_wqh, EPOLLIN); |
9cd75c3c PE |
619 | schedule(); |
620 | ||
621 | spin_lock(&ctx->event_wqh.lock); | |
622 | } | |
623 | __set_current_state(TASK_RUNNING); | |
624 | spin_unlock(&ctx->event_wqh.lock); | |
625 | ||
0cbb4b4f AA |
626 | if (release_new_ctx) { |
627 | struct vm_area_struct *vma; | |
628 | struct mm_struct *mm = release_new_ctx->mm; | |
629 | ||
630 | /* the various vma->vm_userfaultfd_ctx still points to it */ | |
631 | down_write(&mm->mmap_sem); | |
632 | for (vma = mm->mmap; vma; vma = vma->vm_next) | |
31e810aa | 633 | if (vma->vm_userfaultfd_ctx.ctx == release_new_ctx) { |
0cbb4b4f | 634 | vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX; |
31e810aa MR |
635 | vma->vm_flags &= ~(VM_UFFD_WP | VM_UFFD_MISSING); |
636 | } | |
0cbb4b4f AA |
637 | up_write(&mm->mmap_sem); |
638 | ||
639 | userfaultfd_ctx_put(release_new_ctx); | |
640 | } | |
641 | ||
9cd75c3c PE |
642 | /* |
643 | * ctx may go away after this if the userfault pseudo fd is | |
644 | * already released. | |
645 | */ | |
9a69a829 | 646 | out: |
df2cc96e | 647 | WRITE_ONCE(ctx->mmap_changing, false); |
9cd75c3c | 648 | userfaultfd_ctx_put(ctx); |
9cd75c3c PE |
649 | } |
650 | ||
651 | static void userfaultfd_event_complete(struct userfaultfd_ctx *ctx, | |
652 | struct userfaultfd_wait_queue *ewq) | |
653 | { | |
654 | ewq->msg.event = 0; | |
655 | wake_up_locked(&ctx->event_wqh); | |
656 | __remove_wait_queue(&ctx->event_wqh, &ewq->wq); | |
657 | } | |
658 | ||
893e26e6 PE |
659 | int dup_userfaultfd(struct vm_area_struct *vma, struct list_head *fcs) |
660 | { | |
661 | struct userfaultfd_ctx *ctx = NULL, *octx; | |
662 | struct userfaultfd_fork_ctx *fctx; | |
663 | ||
664 | octx = vma->vm_userfaultfd_ctx.ctx; | |
665 | if (!octx || !(octx->features & UFFD_FEATURE_EVENT_FORK)) { | |
666 | vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX; | |
667 | vma->vm_flags &= ~(VM_UFFD_WP | VM_UFFD_MISSING); | |
668 | return 0; | |
669 | } | |
670 | ||
671 | list_for_each_entry(fctx, fcs, list) | |
672 | if (fctx->orig == octx) { | |
673 | ctx = fctx->new; | |
674 | break; | |
675 | } | |
676 | ||
677 | if (!ctx) { | |
678 | fctx = kmalloc(sizeof(*fctx), GFP_KERNEL); | |
679 | if (!fctx) | |
680 | return -ENOMEM; | |
681 | ||
682 | ctx = kmem_cache_alloc(userfaultfd_ctx_cachep, GFP_KERNEL); | |
683 | if (!ctx) { | |
684 | kfree(fctx); | |
685 | return -ENOMEM; | |
686 | } | |
687 | ||
ca880420 | 688 | refcount_set(&ctx->refcount, 1); |
893e26e6 PE |
689 | ctx->flags = octx->flags; |
690 | ctx->state = UFFD_STATE_RUNNING; | |
691 | ctx->features = octx->features; | |
692 | ctx->released = false; | |
df2cc96e | 693 | ctx->mmap_changing = false; |
893e26e6 | 694 | ctx->mm = vma->vm_mm; |
00bb31fa | 695 | mmgrab(ctx->mm); |
893e26e6 PE |
696 | |
697 | userfaultfd_ctx_get(octx); | |
df2cc96e | 698 | WRITE_ONCE(octx->mmap_changing, true); |
893e26e6 PE |
699 | fctx->orig = octx; |
700 | fctx->new = ctx; | |
701 | list_add_tail(&fctx->list, fcs); | |
702 | } | |
703 | ||
704 | vma->vm_userfaultfd_ctx.ctx = ctx; | |
705 | return 0; | |
706 | } | |
707 | ||
8c9e7bb7 | 708 | static void dup_fctx(struct userfaultfd_fork_ctx *fctx) |
893e26e6 PE |
709 | { |
710 | struct userfaultfd_ctx *ctx = fctx->orig; | |
711 | struct userfaultfd_wait_queue ewq; | |
712 | ||
713 | msg_init(&ewq.msg); | |
714 | ||
715 | ewq.msg.event = UFFD_EVENT_FORK; | |
716 | ewq.msg.arg.reserved.reserved1 = (unsigned long)fctx->new; | |
717 | ||
8c9e7bb7 | 718 | userfaultfd_event_wait_completion(ctx, &ewq); |
893e26e6 PE |
719 | } |
720 | ||
721 | void dup_userfaultfd_complete(struct list_head *fcs) | |
722 | { | |
893e26e6 PE |
723 | struct userfaultfd_fork_ctx *fctx, *n; |
724 | ||
725 | list_for_each_entry_safe(fctx, n, fcs, list) { | |
8c9e7bb7 | 726 | dup_fctx(fctx); |
893e26e6 PE |
727 | list_del(&fctx->list); |
728 | kfree(fctx); | |
729 | } | |
730 | } | |
731 | ||
72f87654 PE |
732 | void mremap_userfaultfd_prep(struct vm_area_struct *vma, |
733 | struct vm_userfaultfd_ctx *vm_ctx) | |
734 | { | |
735 | struct userfaultfd_ctx *ctx; | |
736 | ||
737 | ctx = vma->vm_userfaultfd_ctx.ctx; | |
738 | if (ctx && (ctx->features & UFFD_FEATURE_EVENT_REMAP)) { | |
739 | vm_ctx->ctx = ctx; | |
740 | userfaultfd_ctx_get(ctx); | |
df2cc96e | 741 | WRITE_ONCE(ctx->mmap_changing, true); |
72f87654 PE |
742 | } |
743 | } | |
744 | ||
90794bf1 | 745 | void mremap_userfaultfd_complete(struct vm_userfaultfd_ctx *vm_ctx, |
72f87654 PE |
746 | unsigned long from, unsigned long to, |
747 | unsigned long len) | |
748 | { | |
90794bf1 | 749 | struct userfaultfd_ctx *ctx = vm_ctx->ctx; |
72f87654 PE |
750 | struct userfaultfd_wait_queue ewq; |
751 | ||
752 | if (!ctx) | |
753 | return; | |
754 | ||
755 | if (to & ~PAGE_MASK) { | |
756 | userfaultfd_ctx_put(ctx); | |
757 | return; | |
758 | } | |
759 | ||
760 | msg_init(&ewq.msg); | |
761 | ||
762 | ewq.msg.event = UFFD_EVENT_REMAP; | |
763 | ewq.msg.arg.remap.from = from; | |
764 | ewq.msg.arg.remap.to = to; | |
765 | ewq.msg.arg.remap.len = len; | |
766 | ||
767 | userfaultfd_event_wait_completion(ctx, &ewq); | |
768 | } | |
769 | ||
70ccb92f | 770 | bool userfaultfd_remove(struct vm_area_struct *vma, |
d811914d | 771 | unsigned long start, unsigned long end) |
05ce7724 PE |
772 | { |
773 | struct mm_struct *mm = vma->vm_mm; | |
774 | struct userfaultfd_ctx *ctx; | |
775 | struct userfaultfd_wait_queue ewq; | |
776 | ||
777 | ctx = vma->vm_userfaultfd_ctx.ctx; | |
d811914d | 778 | if (!ctx || !(ctx->features & UFFD_FEATURE_EVENT_REMOVE)) |
70ccb92f | 779 | return true; |
05ce7724 PE |
780 | |
781 | userfaultfd_ctx_get(ctx); | |
df2cc96e | 782 | WRITE_ONCE(ctx->mmap_changing, true); |
05ce7724 PE |
783 | up_read(&mm->mmap_sem); |
784 | ||
05ce7724 PE |
785 | msg_init(&ewq.msg); |
786 | ||
d811914d MR |
787 | ewq.msg.event = UFFD_EVENT_REMOVE; |
788 | ewq.msg.arg.remove.start = start; | |
789 | ewq.msg.arg.remove.end = end; | |
05ce7724 PE |
790 | |
791 | userfaultfd_event_wait_completion(ctx, &ewq); | |
792 | ||
70ccb92f | 793 | return false; |
05ce7724 PE |
794 | } |
795 | ||
897ab3e0 MR |
796 | static bool has_unmap_ctx(struct userfaultfd_ctx *ctx, struct list_head *unmaps, |
797 | unsigned long start, unsigned long end) | |
798 | { | |
799 | struct userfaultfd_unmap_ctx *unmap_ctx; | |
800 | ||
801 | list_for_each_entry(unmap_ctx, unmaps, list) | |
802 | if (unmap_ctx->ctx == ctx && unmap_ctx->start == start && | |
803 | unmap_ctx->end == end) | |
804 | return true; | |
805 | ||
806 | return false; | |
807 | } | |
808 | ||
809 | int userfaultfd_unmap_prep(struct vm_area_struct *vma, | |
810 | unsigned long start, unsigned long end, | |
811 | struct list_head *unmaps) | |
812 | { | |
813 | for ( ; vma && vma->vm_start < end; vma = vma->vm_next) { | |
814 | struct userfaultfd_unmap_ctx *unmap_ctx; | |
815 | struct userfaultfd_ctx *ctx = vma->vm_userfaultfd_ctx.ctx; | |
816 | ||
817 | if (!ctx || !(ctx->features & UFFD_FEATURE_EVENT_UNMAP) || | |
818 | has_unmap_ctx(ctx, unmaps, start, end)) | |
819 | continue; | |
820 | ||
821 | unmap_ctx = kzalloc(sizeof(*unmap_ctx), GFP_KERNEL); | |
822 | if (!unmap_ctx) | |
823 | return -ENOMEM; | |
824 | ||
825 | userfaultfd_ctx_get(ctx); | |
df2cc96e | 826 | WRITE_ONCE(ctx->mmap_changing, true); |
897ab3e0 MR |
827 | unmap_ctx->ctx = ctx; |
828 | unmap_ctx->start = start; | |
829 | unmap_ctx->end = end; | |
830 | list_add_tail(&unmap_ctx->list, unmaps); | |
831 | } | |
832 | ||
833 | return 0; | |
834 | } | |
835 | ||
836 | void userfaultfd_unmap_complete(struct mm_struct *mm, struct list_head *uf) | |
837 | { | |
838 | struct userfaultfd_unmap_ctx *ctx, *n; | |
839 | struct userfaultfd_wait_queue ewq; | |
840 | ||
841 | list_for_each_entry_safe(ctx, n, uf, list) { | |
842 | msg_init(&ewq.msg); | |
843 | ||
844 | ewq.msg.event = UFFD_EVENT_UNMAP; | |
845 | ewq.msg.arg.remove.start = ctx->start; | |
846 | ewq.msg.arg.remove.end = ctx->end; | |
847 | ||
848 | userfaultfd_event_wait_completion(ctx->ctx, &ewq); | |
849 | ||
850 | list_del(&ctx->list); | |
851 | kfree(ctx); | |
852 | } | |
853 | } | |
854 | ||
86039bd3 AA |
855 | static int userfaultfd_release(struct inode *inode, struct file *file) |
856 | { | |
857 | struct userfaultfd_ctx *ctx = file->private_data; | |
858 | struct mm_struct *mm = ctx->mm; | |
859 | struct vm_area_struct *vma, *prev; | |
860 | /* len == 0 means wake all */ | |
861 | struct userfaultfd_wake_range range = { .len = 0, }; | |
862 | unsigned long new_flags; | |
863 | ||
6aa7de05 | 864 | WRITE_ONCE(ctx->released, true); |
86039bd3 | 865 | |
d2005e3f ON |
866 | if (!mmget_not_zero(mm)) |
867 | goto wakeup; | |
868 | ||
86039bd3 AA |
869 | /* |
870 | * Flush page faults out of all CPUs. NOTE: all page faults | |
871 | * must be retried without returning VM_FAULT_SIGBUS if | |
872 | * userfaultfd_ctx_get() succeeds but vma->vma_userfault_ctx | |
873 | * changes while handle_userfault released the mmap_sem. So | |
874 | * it's critical that released is set to true (above), before | |
875 | * taking the mmap_sem for writing. | |
876 | */ | |
877 | down_write(&mm->mmap_sem); | |
878 | prev = NULL; | |
879 | for (vma = mm->mmap; vma; vma = vma->vm_next) { | |
880 | cond_resched(); | |
881 | BUG_ON(!!vma->vm_userfaultfd_ctx.ctx ^ | |
882 | !!(vma->vm_flags & (VM_UFFD_MISSING | VM_UFFD_WP))); | |
883 | if (vma->vm_userfaultfd_ctx.ctx != ctx) { | |
884 | prev = vma; | |
885 | continue; | |
886 | } | |
887 | new_flags = vma->vm_flags & ~(VM_UFFD_MISSING | VM_UFFD_WP); | |
888 | prev = vma_merge(mm, prev, vma->vm_start, vma->vm_end, | |
889 | new_flags, vma->anon_vma, | |
890 | vma->vm_file, vma->vm_pgoff, | |
891 | vma_policy(vma), | |
892 | NULL_VM_UFFD_CTX); | |
893 | if (prev) | |
894 | vma = prev; | |
895 | else | |
896 | prev = vma; | |
897 | vma->vm_flags = new_flags; | |
898 | vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX; | |
899 | } | |
900 | up_write(&mm->mmap_sem); | |
d2005e3f ON |
901 | mmput(mm); |
902 | wakeup: | |
86039bd3 | 903 | /* |
15b726ef | 904 | * After no new page faults can wait on this fault_*wqh, flush |
86039bd3 | 905 | * the last page faults that may have been already waiting on |
15b726ef | 906 | * the fault_*wqh. |
86039bd3 | 907 | */ |
15b726ef | 908 | spin_lock(&ctx->fault_pending_wqh.lock); |
ac5be6b4 | 909 | __wake_up_locked_key(&ctx->fault_pending_wqh, TASK_NORMAL, &range); |
c430d1e8 | 910 | __wake_up(&ctx->fault_wqh, TASK_NORMAL, 1, &range); |
15b726ef | 911 | spin_unlock(&ctx->fault_pending_wqh.lock); |
86039bd3 | 912 | |
5a18b64e MR |
913 | /* Flush pending events that may still wait on event_wqh */ |
914 | wake_up_all(&ctx->event_wqh); | |
915 | ||
a9a08845 | 916 | wake_up_poll(&ctx->fd_wqh, EPOLLHUP); |
86039bd3 AA |
917 | userfaultfd_ctx_put(ctx); |
918 | return 0; | |
919 | } | |
920 | ||
15b726ef | 921 | /* fault_pending_wqh.lock must be hold by the caller */ |
6dcc27fd PE |
922 | static inline struct userfaultfd_wait_queue *find_userfault_in( |
923 | wait_queue_head_t *wqh) | |
86039bd3 | 924 | { |
ac6424b9 | 925 | wait_queue_entry_t *wq; |
15b726ef | 926 | struct userfaultfd_wait_queue *uwq; |
86039bd3 | 927 | |
456a7378 | 928 | lockdep_assert_held(&wqh->lock); |
86039bd3 | 929 | |
15b726ef | 930 | uwq = NULL; |
6dcc27fd | 931 | if (!waitqueue_active(wqh)) |
15b726ef AA |
932 | goto out; |
933 | /* walk in reverse to provide FIFO behavior to read userfaults */ | |
2055da97 | 934 | wq = list_last_entry(&wqh->head, typeof(*wq), entry); |
15b726ef AA |
935 | uwq = container_of(wq, struct userfaultfd_wait_queue, wq); |
936 | out: | |
937 | return uwq; | |
86039bd3 | 938 | } |
6dcc27fd PE |
939 | |
940 | static inline struct userfaultfd_wait_queue *find_userfault( | |
941 | struct userfaultfd_ctx *ctx) | |
942 | { | |
943 | return find_userfault_in(&ctx->fault_pending_wqh); | |
944 | } | |
86039bd3 | 945 | |
9cd75c3c PE |
946 | static inline struct userfaultfd_wait_queue *find_userfault_evt( |
947 | struct userfaultfd_ctx *ctx) | |
948 | { | |
949 | return find_userfault_in(&ctx->event_wqh); | |
950 | } | |
951 | ||
076ccb76 | 952 | static __poll_t userfaultfd_poll(struct file *file, poll_table *wait) |
86039bd3 AA |
953 | { |
954 | struct userfaultfd_ctx *ctx = file->private_data; | |
076ccb76 | 955 | __poll_t ret; |
86039bd3 AA |
956 | |
957 | poll_wait(file, &ctx->fd_wqh, wait); | |
958 | ||
959 | switch (ctx->state) { | |
960 | case UFFD_STATE_WAIT_API: | |
a9a08845 | 961 | return EPOLLERR; |
86039bd3 | 962 | case UFFD_STATE_RUNNING: |
ba85c702 AA |
963 | /* |
964 | * poll() never guarantees that read won't block. | |
965 | * userfaults can be waken before they're read(). | |
966 | */ | |
967 | if (unlikely(!(file->f_flags & O_NONBLOCK))) | |
a9a08845 | 968 | return EPOLLERR; |
15b726ef AA |
969 | /* |
970 | * lockless access to see if there are pending faults | |
971 | * __pollwait last action is the add_wait_queue but | |
972 | * the spin_unlock would allow the waitqueue_active to | |
973 | * pass above the actual list_add inside | |
974 | * add_wait_queue critical section. So use a full | |
975 | * memory barrier to serialize the list_add write of | |
976 | * add_wait_queue() with the waitqueue_active read | |
977 | * below. | |
978 | */ | |
979 | ret = 0; | |
980 | smp_mb(); | |
981 | if (waitqueue_active(&ctx->fault_pending_wqh)) | |
a9a08845 | 982 | ret = EPOLLIN; |
9cd75c3c | 983 | else if (waitqueue_active(&ctx->event_wqh)) |
a9a08845 | 984 | ret = EPOLLIN; |
9cd75c3c | 985 | |
86039bd3 AA |
986 | return ret; |
987 | default: | |
8474901a | 988 | WARN_ON_ONCE(1); |
a9a08845 | 989 | return EPOLLERR; |
86039bd3 AA |
990 | } |
991 | } | |
992 | ||
893e26e6 PE |
993 | static const struct file_operations userfaultfd_fops; |
994 | ||
995 | static int resolve_userfault_fork(struct userfaultfd_ctx *ctx, | |
996 | struct userfaultfd_ctx *new, | |
997 | struct uffd_msg *msg) | |
998 | { | |
999 | int fd; | |
893e26e6 | 1000 | |
284cd241 EB |
1001 | fd = anon_inode_getfd("[userfaultfd]", &userfaultfd_fops, new, |
1002 | O_RDWR | (new->flags & UFFD_SHARED_FCNTL_FLAGS)); | |
893e26e6 PE |
1003 | if (fd < 0) |
1004 | return fd; | |
1005 | ||
893e26e6 PE |
1006 | msg->arg.reserved.reserved1 = 0; |
1007 | msg->arg.fork.ufd = fd; | |
893e26e6 PE |
1008 | return 0; |
1009 | } | |
1010 | ||
86039bd3 | 1011 | static ssize_t userfaultfd_ctx_read(struct userfaultfd_ctx *ctx, int no_wait, |
a9b85f94 | 1012 | struct uffd_msg *msg) |
86039bd3 AA |
1013 | { |
1014 | ssize_t ret; | |
1015 | DECLARE_WAITQUEUE(wait, current); | |
15b726ef | 1016 | struct userfaultfd_wait_queue *uwq; |
893e26e6 PE |
1017 | /* |
1018 | * Handling fork event requires sleeping operations, so | |
1019 | * we drop the event_wqh lock, then do these ops, then | |
1020 | * lock it back and wake up the waiter. While the lock is | |
1021 | * dropped the ewq may go away so we keep track of it | |
1022 | * carefully. | |
1023 | */ | |
1024 | LIST_HEAD(fork_event); | |
1025 | struct userfaultfd_ctx *fork_nctx = NULL; | |
86039bd3 | 1026 | |
15b726ef | 1027 | /* always take the fd_wqh lock before the fault_pending_wqh lock */ |
ae62c16e | 1028 | spin_lock_irq(&ctx->fd_wqh.lock); |
86039bd3 AA |
1029 | __add_wait_queue(&ctx->fd_wqh, &wait); |
1030 | for (;;) { | |
1031 | set_current_state(TASK_INTERRUPTIBLE); | |
15b726ef AA |
1032 | spin_lock(&ctx->fault_pending_wqh.lock); |
1033 | uwq = find_userfault(ctx); | |
1034 | if (uwq) { | |
2c5b7e1b AA |
1035 | /* |
1036 | * Use a seqcount to repeat the lockless check | |
1037 | * in wake_userfault() to avoid missing | |
1038 | * wakeups because during the refile both | |
1039 | * waitqueue could become empty if this is the | |
1040 | * only userfault. | |
1041 | */ | |
1042 | write_seqcount_begin(&ctx->refile_seq); | |
1043 | ||
86039bd3 | 1044 | /* |
15b726ef AA |
1045 | * The fault_pending_wqh.lock prevents the uwq |
1046 | * to disappear from under us. | |
1047 | * | |
1048 | * Refile this userfault from | |
1049 | * fault_pending_wqh to fault_wqh, it's not | |
1050 | * pending anymore after we read it. | |
1051 | * | |
1052 | * Use list_del() by hand (as | |
1053 | * userfaultfd_wake_function also uses | |
1054 | * list_del_init() by hand) to be sure nobody | |
1055 | * changes __remove_wait_queue() to use | |
1056 | * list_del_init() in turn breaking the | |
1057 | * !list_empty_careful() check in | |
2055da97 | 1058 | * handle_userfault(). The uwq->wq.head list |
15b726ef AA |
1059 | * must never be empty at any time during the |
1060 | * refile, or the waitqueue could disappear | |
1061 | * from under us. The "wait_queue_head_t" | |
1062 | * parameter of __remove_wait_queue() is unused | |
1063 | * anyway. | |
86039bd3 | 1064 | */ |
2055da97 | 1065 | list_del(&uwq->wq.entry); |
c430d1e8 | 1066 | add_wait_queue(&ctx->fault_wqh, &uwq->wq); |
15b726ef | 1067 | |
2c5b7e1b AA |
1068 | write_seqcount_end(&ctx->refile_seq); |
1069 | ||
a9b85f94 AA |
1070 | /* careful to always initialize msg if ret == 0 */ |
1071 | *msg = uwq->msg; | |
15b726ef | 1072 | spin_unlock(&ctx->fault_pending_wqh.lock); |
86039bd3 AA |
1073 | ret = 0; |
1074 | break; | |
1075 | } | |
15b726ef | 1076 | spin_unlock(&ctx->fault_pending_wqh.lock); |
9cd75c3c PE |
1077 | |
1078 | spin_lock(&ctx->event_wqh.lock); | |
1079 | uwq = find_userfault_evt(ctx); | |
1080 | if (uwq) { | |
1081 | *msg = uwq->msg; | |
1082 | ||
893e26e6 PE |
1083 | if (uwq->msg.event == UFFD_EVENT_FORK) { |
1084 | fork_nctx = (struct userfaultfd_ctx *) | |
1085 | (unsigned long) | |
1086 | uwq->msg.arg.reserved.reserved1; | |
2055da97 | 1087 | list_move(&uwq->wq.entry, &fork_event); |
384632e6 AA |
1088 | /* |
1089 | * fork_nctx can be freed as soon as | |
1090 | * we drop the lock, unless we take a | |
1091 | * reference on it. | |
1092 | */ | |
1093 | userfaultfd_ctx_get(fork_nctx); | |
893e26e6 PE |
1094 | spin_unlock(&ctx->event_wqh.lock); |
1095 | ret = 0; | |
1096 | break; | |
1097 | } | |
1098 | ||
9cd75c3c PE |
1099 | userfaultfd_event_complete(ctx, uwq); |
1100 | spin_unlock(&ctx->event_wqh.lock); | |
1101 | ret = 0; | |
1102 | break; | |
1103 | } | |
1104 | spin_unlock(&ctx->event_wqh.lock); | |
1105 | ||
86039bd3 AA |
1106 | if (signal_pending(current)) { |
1107 | ret = -ERESTARTSYS; | |
1108 | break; | |
1109 | } | |
1110 | if (no_wait) { | |
1111 | ret = -EAGAIN; | |
1112 | break; | |
1113 | } | |
ae62c16e | 1114 | spin_unlock_irq(&ctx->fd_wqh.lock); |
86039bd3 | 1115 | schedule(); |
ae62c16e | 1116 | spin_lock_irq(&ctx->fd_wqh.lock); |
86039bd3 AA |
1117 | } |
1118 | __remove_wait_queue(&ctx->fd_wqh, &wait); | |
1119 | __set_current_state(TASK_RUNNING); | |
ae62c16e | 1120 | spin_unlock_irq(&ctx->fd_wqh.lock); |
86039bd3 | 1121 | |
893e26e6 PE |
1122 | if (!ret && msg->event == UFFD_EVENT_FORK) { |
1123 | ret = resolve_userfault_fork(ctx, fork_nctx, msg); | |
384632e6 AA |
1124 | spin_lock(&ctx->event_wqh.lock); |
1125 | if (!list_empty(&fork_event)) { | |
1126 | /* | |
1127 | * The fork thread didn't abort, so we can | |
1128 | * drop the temporary refcount. | |
1129 | */ | |
1130 | userfaultfd_ctx_put(fork_nctx); | |
1131 | ||
1132 | uwq = list_first_entry(&fork_event, | |
1133 | typeof(*uwq), | |
1134 | wq.entry); | |
1135 | /* | |
1136 | * If fork_event list wasn't empty and in turn | |
1137 | * the event wasn't already released by fork | |
1138 | * (the event is allocated on fork kernel | |
1139 | * stack), put the event back to its place in | |
1140 | * the event_wq. fork_event head will be freed | |
1141 | * as soon as we return so the event cannot | |
1142 | * stay queued there no matter the current | |
1143 | * "ret" value. | |
1144 | */ | |
1145 | list_del(&uwq->wq.entry); | |
1146 | __add_wait_queue(&ctx->event_wqh, &uwq->wq); | |
893e26e6 | 1147 | |
384632e6 AA |
1148 | /* |
1149 | * Leave the event in the waitqueue and report | |
1150 | * error to userland if we failed to resolve | |
1151 | * the userfault fork. | |
1152 | */ | |
1153 | if (likely(!ret)) | |
893e26e6 | 1154 | userfaultfd_event_complete(ctx, uwq); |
384632e6 AA |
1155 | } else { |
1156 | /* | |
1157 | * Here the fork thread aborted and the | |
1158 | * refcount from the fork thread on fork_nctx | |
1159 | * has already been released. We still hold | |
1160 | * the reference we took before releasing the | |
1161 | * lock above. If resolve_userfault_fork | |
1162 | * failed we've to drop it because the | |
1163 | * fork_nctx has to be freed in such case. If | |
1164 | * it succeeded we'll hold it because the new | |
1165 | * uffd references it. | |
1166 | */ | |
1167 | if (ret) | |
1168 | userfaultfd_ctx_put(fork_nctx); | |
893e26e6 | 1169 | } |
384632e6 | 1170 | spin_unlock(&ctx->event_wqh.lock); |
893e26e6 PE |
1171 | } |
1172 | ||
86039bd3 AA |
1173 | return ret; |
1174 | } | |
1175 | ||
1176 | static ssize_t userfaultfd_read(struct file *file, char __user *buf, | |
1177 | size_t count, loff_t *ppos) | |
1178 | { | |
1179 | struct userfaultfd_ctx *ctx = file->private_data; | |
1180 | ssize_t _ret, ret = 0; | |
a9b85f94 | 1181 | struct uffd_msg msg; |
86039bd3 AA |
1182 | int no_wait = file->f_flags & O_NONBLOCK; |
1183 | ||
1184 | if (ctx->state == UFFD_STATE_WAIT_API) | |
1185 | return -EINVAL; | |
86039bd3 AA |
1186 | |
1187 | for (;;) { | |
a9b85f94 | 1188 | if (count < sizeof(msg)) |
86039bd3 | 1189 | return ret ? ret : -EINVAL; |
a9b85f94 | 1190 | _ret = userfaultfd_ctx_read(ctx, no_wait, &msg); |
86039bd3 AA |
1191 | if (_ret < 0) |
1192 | return ret ? ret : _ret; | |
a9b85f94 | 1193 | if (copy_to_user((__u64 __user *) buf, &msg, sizeof(msg))) |
86039bd3 | 1194 | return ret ? ret : -EFAULT; |
a9b85f94 AA |
1195 | ret += sizeof(msg); |
1196 | buf += sizeof(msg); | |
1197 | count -= sizeof(msg); | |
86039bd3 AA |
1198 | /* |
1199 | * Allow to read more than one fault at time but only | |
1200 | * block if waiting for the very first one. | |
1201 | */ | |
1202 | no_wait = O_NONBLOCK; | |
1203 | } | |
1204 | } | |
1205 | ||
1206 | static void __wake_userfault(struct userfaultfd_ctx *ctx, | |
1207 | struct userfaultfd_wake_range *range) | |
1208 | { | |
15b726ef | 1209 | spin_lock(&ctx->fault_pending_wqh.lock); |
86039bd3 | 1210 | /* wake all in the range and autoremove */ |
15b726ef | 1211 | if (waitqueue_active(&ctx->fault_pending_wqh)) |
ac5be6b4 | 1212 | __wake_up_locked_key(&ctx->fault_pending_wqh, TASK_NORMAL, |
15b726ef AA |
1213 | range); |
1214 | if (waitqueue_active(&ctx->fault_wqh)) | |
c430d1e8 | 1215 | __wake_up(&ctx->fault_wqh, TASK_NORMAL, 1, range); |
15b726ef | 1216 | spin_unlock(&ctx->fault_pending_wqh.lock); |
86039bd3 AA |
1217 | } |
1218 | ||
1219 | static __always_inline void wake_userfault(struct userfaultfd_ctx *ctx, | |
1220 | struct userfaultfd_wake_range *range) | |
1221 | { | |
2c5b7e1b AA |
1222 | unsigned seq; |
1223 | bool need_wakeup; | |
1224 | ||
86039bd3 AA |
1225 | /* |
1226 | * To be sure waitqueue_active() is not reordered by the CPU | |
1227 | * before the pagetable update, use an explicit SMP memory | |
1228 | * barrier here. PT lock release or up_read(mmap_sem) still | |
1229 | * have release semantics that can allow the | |
1230 | * waitqueue_active() to be reordered before the pte update. | |
1231 | */ | |
1232 | smp_mb(); | |
1233 | ||
1234 | /* | |
1235 | * Use waitqueue_active because it's very frequent to | |
1236 | * change the address space atomically even if there are no | |
1237 | * userfaults yet. So we take the spinlock only when we're | |
1238 | * sure we've userfaults to wake. | |
1239 | */ | |
2c5b7e1b AA |
1240 | do { |
1241 | seq = read_seqcount_begin(&ctx->refile_seq); | |
1242 | need_wakeup = waitqueue_active(&ctx->fault_pending_wqh) || | |
1243 | waitqueue_active(&ctx->fault_wqh); | |
1244 | cond_resched(); | |
1245 | } while (read_seqcount_retry(&ctx->refile_seq, seq)); | |
1246 | if (need_wakeup) | |
86039bd3 AA |
1247 | __wake_userfault(ctx, range); |
1248 | } | |
1249 | ||
1250 | static __always_inline int validate_range(struct mm_struct *mm, | |
1251 | __u64 start, __u64 len) | |
1252 | { | |
1253 | __u64 task_size = mm->task_size; | |
1254 | ||
1255 | if (start & ~PAGE_MASK) | |
1256 | return -EINVAL; | |
1257 | if (len & ~PAGE_MASK) | |
1258 | return -EINVAL; | |
1259 | if (!len) | |
1260 | return -EINVAL; | |
1261 | if (start < mmap_min_addr) | |
1262 | return -EINVAL; | |
1263 | if (start >= task_size) | |
1264 | return -EINVAL; | |
1265 | if (len > task_size - start) | |
1266 | return -EINVAL; | |
1267 | return 0; | |
1268 | } | |
1269 | ||
ba6907db MR |
1270 | static inline bool vma_can_userfault(struct vm_area_struct *vma) |
1271 | { | |
cac67329 MR |
1272 | return vma_is_anonymous(vma) || is_vm_hugetlb_page(vma) || |
1273 | vma_is_shmem(vma); | |
ba6907db MR |
1274 | } |
1275 | ||
86039bd3 AA |
1276 | static int userfaultfd_register(struct userfaultfd_ctx *ctx, |
1277 | unsigned long arg) | |
1278 | { | |
1279 | struct mm_struct *mm = ctx->mm; | |
1280 | struct vm_area_struct *vma, *prev, *cur; | |
1281 | int ret; | |
1282 | struct uffdio_register uffdio_register; | |
1283 | struct uffdio_register __user *user_uffdio_register; | |
1284 | unsigned long vm_flags, new_flags; | |
1285 | bool found; | |
ce53e8e6 | 1286 | bool basic_ioctls; |
86039bd3 AA |
1287 | unsigned long start, end, vma_end; |
1288 | ||
1289 | user_uffdio_register = (struct uffdio_register __user *) arg; | |
1290 | ||
1291 | ret = -EFAULT; | |
1292 | if (copy_from_user(&uffdio_register, user_uffdio_register, | |
1293 | sizeof(uffdio_register)-sizeof(__u64))) | |
1294 | goto out; | |
1295 | ||
1296 | ret = -EINVAL; | |
1297 | if (!uffdio_register.mode) | |
1298 | goto out; | |
1299 | if (uffdio_register.mode & ~(UFFDIO_REGISTER_MODE_MISSING| | |
1300 | UFFDIO_REGISTER_MODE_WP)) | |
1301 | goto out; | |
1302 | vm_flags = 0; | |
1303 | if (uffdio_register.mode & UFFDIO_REGISTER_MODE_MISSING) | |
1304 | vm_flags |= VM_UFFD_MISSING; | |
1305 | if (uffdio_register.mode & UFFDIO_REGISTER_MODE_WP) { | |
1306 | vm_flags |= VM_UFFD_WP; | |
1307 | /* | |
1308 | * FIXME: remove the below error constraint by | |
1309 | * implementing the wprotect tracking mode. | |
1310 | */ | |
1311 | ret = -EINVAL; | |
1312 | goto out; | |
1313 | } | |
1314 | ||
1315 | ret = validate_range(mm, uffdio_register.range.start, | |
1316 | uffdio_register.range.len); | |
1317 | if (ret) | |
1318 | goto out; | |
1319 | ||
1320 | start = uffdio_register.range.start; | |
1321 | end = start + uffdio_register.range.len; | |
1322 | ||
d2005e3f ON |
1323 | ret = -ENOMEM; |
1324 | if (!mmget_not_zero(mm)) | |
1325 | goto out; | |
1326 | ||
86039bd3 AA |
1327 | down_write(&mm->mmap_sem); |
1328 | vma = find_vma_prev(mm, start, &prev); | |
86039bd3 AA |
1329 | if (!vma) |
1330 | goto out_unlock; | |
1331 | ||
1332 | /* check that there's at least one vma in the range */ | |
1333 | ret = -EINVAL; | |
1334 | if (vma->vm_start >= end) | |
1335 | goto out_unlock; | |
1336 | ||
cab350af MK |
1337 | /* |
1338 | * If the first vma contains huge pages, make sure start address | |
1339 | * is aligned to huge page size. | |
1340 | */ | |
1341 | if (is_vm_hugetlb_page(vma)) { | |
1342 | unsigned long vma_hpagesize = vma_kernel_pagesize(vma); | |
1343 | ||
1344 | if (start & (vma_hpagesize - 1)) | |
1345 | goto out_unlock; | |
1346 | } | |
1347 | ||
86039bd3 AA |
1348 | /* |
1349 | * Search for not compatible vmas. | |
86039bd3 AA |
1350 | */ |
1351 | found = false; | |
ce53e8e6 | 1352 | basic_ioctls = false; |
86039bd3 AA |
1353 | for (cur = vma; cur && cur->vm_start < end; cur = cur->vm_next) { |
1354 | cond_resched(); | |
1355 | ||
1356 | BUG_ON(!!cur->vm_userfaultfd_ctx.ctx ^ | |
1357 | !!(cur->vm_flags & (VM_UFFD_MISSING | VM_UFFD_WP))); | |
1358 | ||
1359 | /* check not compatible vmas */ | |
1360 | ret = -EINVAL; | |
ba6907db | 1361 | if (!vma_can_userfault(cur)) |
86039bd3 | 1362 | goto out_unlock; |
29ec9066 AA |
1363 | |
1364 | /* | |
1365 | * UFFDIO_COPY will fill file holes even without | |
1366 | * PROT_WRITE. This check enforces that if this is a | |
1367 | * MAP_SHARED, the process has write permission to the backing | |
1368 | * file. If VM_MAYWRITE is set it also enforces that on a | |
1369 | * MAP_SHARED vma: there is no F_WRITE_SEAL and no further | |
1370 | * F_WRITE_SEAL can be taken until the vma is destroyed. | |
1371 | */ | |
1372 | ret = -EPERM; | |
1373 | if (unlikely(!(cur->vm_flags & VM_MAYWRITE))) | |
1374 | goto out_unlock; | |
1375 | ||
cab350af MK |
1376 | /* |
1377 | * If this vma contains ending address, and huge pages | |
1378 | * check alignment. | |
1379 | */ | |
1380 | if (is_vm_hugetlb_page(cur) && end <= cur->vm_end && | |
1381 | end > cur->vm_start) { | |
1382 | unsigned long vma_hpagesize = vma_kernel_pagesize(cur); | |
1383 | ||
1384 | ret = -EINVAL; | |
1385 | ||
1386 | if (end & (vma_hpagesize - 1)) | |
1387 | goto out_unlock; | |
1388 | } | |
86039bd3 AA |
1389 | |
1390 | /* | |
1391 | * Check that this vma isn't already owned by a | |
1392 | * different userfaultfd. We can't allow more than one | |
1393 | * userfaultfd to own a single vma simultaneously or we | |
1394 | * wouldn't know which one to deliver the userfaults to. | |
1395 | */ | |
1396 | ret = -EBUSY; | |
1397 | if (cur->vm_userfaultfd_ctx.ctx && | |
1398 | cur->vm_userfaultfd_ctx.ctx != ctx) | |
1399 | goto out_unlock; | |
1400 | ||
cab350af MK |
1401 | /* |
1402 | * Note vmas containing huge pages | |
1403 | */ | |
ce53e8e6 MR |
1404 | if (is_vm_hugetlb_page(cur)) |
1405 | basic_ioctls = true; | |
cab350af | 1406 | |
86039bd3 AA |
1407 | found = true; |
1408 | } | |
1409 | BUG_ON(!found); | |
1410 | ||
1411 | if (vma->vm_start < start) | |
1412 | prev = vma; | |
1413 | ||
1414 | ret = 0; | |
1415 | do { | |
1416 | cond_resched(); | |
1417 | ||
ba6907db | 1418 | BUG_ON(!vma_can_userfault(vma)); |
86039bd3 AA |
1419 | BUG_ON(vma->vm_userfaultfd_ctx.ctx && |
1420 | vma->vm_userfaultfd_ctx.ctx != ctx); | |
29ec9066 | 1421 | WARN_ON(!(vma->vm_flags & VM_MAYWRITE)); |
86039bd3 AA |
1422 | |
1423 | /* | |
1424 | * Nothing to do: this vma is already registered into this | |
1425 | * userfaultfd and with the right tracking mode too. | |
1426 | */ | |
1427 | if (vma->vm_userfaultfd_ctx.ctx == ctx && | |
1428 | (vma->vm_flags & vm_flags) == vm_flags) | |
1429 | goto skip; | |
1430 | ||
1431 | if (vma->vm_start > start) | |
1432 | start = vma->vm_start; | |
1433 | vma_end = min(end, vma->vm_end); | |
1434 | ||
1435 | new_flags = (vma->vm_flags & ~vm_flags) | vm_flags; | |
1436 | prev = vma_merge(mm, prev, start, vma_end, new_flags, | |
1437 | vma->anon_vma, vma->vm_file, vma->vm_pgoff, | |
1438 | vma_policy(vma), | |
1439 | ((struct vm_userfaultfd_ctx){ ctx })); | |
1440 | if (prev) { | |
1441 | vma = prev; | |
1442 | goto next; | |
1443 | } | |
1444 | if (vma->vm_start < start) { | |
1445 | ret = split_vma(mm, vma, start, 1); | |
1446 | if (ret) | |
1447 | break; | |
1448 | } | |
1449 | if (vma->vm_end > end) { | |
1450 | ret = split_vma(mm, vma, end, 0); | |
1451 | if (ret) | |
1452 | break; | |
1453 | } | |
1454 | next: | |
1455 | /* | |
1456 | * In the vma_merge() successful mprotect-like case 8: | |
1457 | * the next vma was merged into the current one and | |
1458 | * the current one has not been updated yet. | |
1459 | */ | |
1460 | vma->vm_flags = new_flags; | |
1461 | vma->vm_userfaultfd_ctx.ctx = ctx; | |
1462 | ||
1463 | skip: | |
1464 | prev = vma; | |
1465 | start = vma->vm_end; | |
1466 | vma = vma->vm_next; | |
1467 | } while (vma && vma->vm_start < end); | |
1468 | out_unlock: | |
1469 | up_write(&mm->mmap_sem); | |
d2005e3f | 1470 | mmput(mm); |
86039bd3 AA |
1471 | if (!ret) { |
1472 | /* | |
1473 | * Now that we scanned all vmas we can already tell | |
1474 | * userland which ioctls methods are guaranteed to | |
1475 | * succeed on this range. | |
1476 | */ | |
ce53e8e6 | 1477 | if (put_user(basic_ioctls ? UFFD_API_RANGE_IOCTLS_BASIC : |
cab350af | 1478 | UFFD_API_RANGE_IOCTLS, |
86039bd3 AA |
1479 | &user_uffdio_register->ioctls)) |
1480 | ret = -EFAULT; | |
1481 | } | |
1482 | out: | |
1483 | return ret; | |
1484 | } | |
1485 | ||
1486 | static int userfaultfd_unregister(struct userfaultfd_ctx *ctx, | |
1487 | unsigned long arg) | |
1488 | { | |
1489 | struct mm_struct *mm = ctx->mm; | |
1490 | struct vm_area_struct *vma, *prev, *cur; | |
1491 | int ret; | |
1492 | struct uffdio_range uffdio_unregister; | |
1493 | unsigned long new_flags; | |
1494 | bool found; | |
1495 | unsigned long start, end, vma_end; | |
1496 | const void __user *buf = (void __user *)arg; | |
1497 | ||
1498 | ret = -EFAULT; | |
1499 | if (copy_from_user(&uffdio_unregister, buf, sizeof(uffdio_unregister))) | |
1500 | goto out; | |
1501 | ||
1502 | ret = validate_range(mm, uffdio_unregister.start, | |
1503 | uffdio_unregister.len); | |
1504 | if (ret) | |
1505 | goto out; | |
1506 | ||
1507 | start = uffdio_unregister.start; | |
1508 | end = start + uffdio_unregister.len; | |
1509 | ||
d2005e3f ON |
1510 | ret = -ENOMEM; |
1511 | if (!mmget_not_zero(mm)) | |
1512 | goto out; | |
1513 | ||
86039bd3 AA |
1514 | down_write(&mm->mmap_sem); |
1515 | vma = find_vma_prev(mm, start, &prev); | |
86039bd3 AA |
1516 | if (!vma) |
1517 | goto out_unlock; | |
1518 | ||
1519 | /* check that there's at least one vma in the range */ | |
1520 | ret = -EINVAL; | |
1521 | if (vma->vm_start >= end) | |
1522 | goto out_unlock; | |
1523 | ||
cab350af MK |
1524 | /* |
1525 | * If the first vma contains huge pages, make sure start address | |
1526 | * is aligned to huge page size. | |
1527 | */ | |
1528 | if (is_vm_hugetlb_page(vma)) { | |
1529 | unsigned long vma_hpagesize = vma_kernel_pagesize(vma); | |
1530 | ||
1531 | if (start & (vma_hpagesize - 1)) | |
1532 | goto out_unlock; | |
1533 | } | |
1534 | ||
86039bd3 AA |
1535 | /* |
1536 | * Search for not compatible vmas. | |
86039bd3 AA |
1537 | */ |
1538 | found = false; | |
1539 | ret = -EINVAL; | |
1540 | for (cur = vma; cur && cur->vm_start < end; cur = cur->vm_next) { | |
1541 | cond_resched(); | |
1542 | ||
1543 | BUG_ON(!!cur->vm_userfaultfd_ctx.ctx ^ | |
1544 | !!(cur->vm_flags & (VM_UFFD_MISSING | VM_UFFD_WP))); | |
1545 | ||
1546 | /* | |
1547 | * Check not compatible vmas, not strictly required | |
1548 | * here as not compatible vmas cannot have an | |
1549 | * userfaultfd_ctx registered on them, but this | |
1550 | * provides for more strict behavior to notice | |
1551 | * unregistration errors. | |
1552 | */ | |
ba6907db | 1553 | if (!vma_can_userfault(cur)) |
86039bd3 AA |
1554 | goto out_unlock; |
1555 | ||
1556 | found = true; | |
1557 | } | |
1558 | BUG_ON(!found); | |
1559 | ||
1560 | if (vma->vm_start < start) | |
1561 | prev = vma; | |
1562 | ||
1563 | ret = 0; | |
1564 | do { | |
1565 | cond_resched(); | |
1566 | ||
ba6907db | 1567 | BUG_ON(!vma_can_userfault(vma)); |
86039bd3 AA |
1568 | |
1569 | /* | |
1570 | * Nothing to do: this vma is already registered into this | |
1571 | * userfaultfd and with the right tracking mode too. | |
1572 | */ | |
1573 | if (!vma->vm_userfaultfd_ctx.ctx) | |
1574 | goto skip; | |
1575 | ||
01e881f5 AA |
1576 | WARN_ON(!(vma->vm_flags & VM_MAYWRITE)); |
1577 | ||
86039bd3 AA |
1578 | if (vma->vm_start > start) |
1579 | start = vma->vm_start; | |
1580 | vma_end = min(end, vma->vm_end); | |
1581 | ||
09fa5296 AA |
1582 | if (userfaultfd_missing(vma)) { |
1583 | /* | |
1584 | * Wake any concurrent pending userfault while | |
1585 | * we unregister, so they will not hang | |
1586 | * permanently and it avoids userland to call | |
1587 | * UFFDIO_WAKE explicitly. | |
1588 | */ | |
1589 | struct userfaultfd_wake_range range; | |
1590 | range.start = start; | |
1591 | range.len = vma_end - start; | |
1592 | wake_userfault(vma->vm_userfaultfd_ctx.ctx, &range); | |
1593 | } | |
1594 | ||
86039bd3 AA |
1595 | new_flags = vma->vm_flags & ~(VM_UFFD_MISSING | VM_UFFD_WP); |
1596 | prev = vma_merge(mm, prev, start, vma_end, new_flags, | |
1597 | vma->anon_vma, vma->vm_file, vma->vm_pgoff, | |
1598 | vma_policy(vma), | |
1599 | NULL_VM_UFFD_CTX); | |
1600 | if (prev) { | |
1601 | vma = prev; | |
1602 | goto next; | |
1603 | } | |
1604 | if (vma->vm_start < start) { | |
1605 | ret = split_vma(mm, vma, start, 1); | |
1606 | if (ret) | |
1607 | break; | |
1608 | } | |
1609 | if (vma->vm_end > end) { | |
1610 | ret = split_vma(mm, vma, end, 0); | |
1611 | if (ret) | |
1612 | break; | |
1613 | } | |
1614 | next: | |
1615 | /* | |
1616 | * In the vma_merge() successful mprotect-like case 8: | |
1617 | * the next vma was merged into the current one and | |
1618 | * the current one has not been updated yet. | |
1619 | */ | |
1620 | vma->vm_flags = new_flags; | |
1621 | vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX; | |
1622 | ||
1623 | skip: | |
1624 | prev = vma; | |
1625 | start = vma->vm_end; | |
1626 | vma = vma->vm_next; | |
1627 | } while (vma && vma->vm_start < end); | |
1628 | out_unlock: | |
1629 | up_write(&mm->mmap_sem); | |
d2005e3f | 1630 | mmput(mm); |
86039bd3 AA |
1631 | out: |
1632 | return ret; | |
1633 | } | |
1634 | ||
1635 | /* | |
ba85c702 AA |
1636 | * userfaultfd_wake may be used in combination with the |
1637 | * UFFDIO_*_MODE_DONTWAKE to wakeup userfaults in batches. | |
86039bd3 AA |
1638 | */ |
1639 | static int userfaultfd_wake(struct userfaultfd_ctx *ctx, | |
1640 | unsigned long arg) | |
1641 | { | |
1642 | int ret; | |
1643 | struct uffdio_range uffdio_wake; | |
1644 | struct userfaultfd_wake_range range; | |
1645 | const void __user *buf = (void __user *)arg; | |
1646 | ||
1647 | ret = -EFAULT; | |
1648 | if (copy_from_user(&uffdio_wake, buf, sizeof(uffdio_wake))) | |
1649 | goto out; | |
1650 | ||
1651 | ret = validate_range(ctx->mm, uffdio_wake.start, uffdio_wake.len); | |
1652 | if (ret) | |
1653 | goto out; | |
1654 | ||
1655 | range.start = uffdio_wake.start; | |
1656 | range.len = uffdio_wake.len; | |
1657 | ||
1658 | /* | |
1659 | * len == 0 means wake all and we don't want to wake all here, | |
1660 | * so check it again to be sure. | |
1661 | */ | |
1662 | VM_BUG_ON(!range.len); | |
1663 | ||
1664 | wake_userfault(ctx, &range); | |
1665 | ret = 0; | |
1666 | ||
1667 | out: | |
1668 | return ret; | |
1669 | } | |
1670 | ||
ad465cae AA |
1671 | static int userfaultfd_copy(struct userfaultfd_ctx *ctx, |
1672 | unsigned long arg) | |
1673 | { | |
1674 | __s64 ret; | |
1675 | struct uffdio_copy uffdio_copy; | |
1676 | struct uffdio_copy __user *user_uffdio_copy; | |
1677 | struct userfaultfd_wake_range range; | |
1678 | ||
1679 | user_uffdio_copy = (struct uffdio_copy __user *) arg; | |
1680 | ||
df2cc96e MR |
1681 | ret = -EAGAIN; |
1682 | if (READ_ONCE(ctx->mmap_changing)) | |
1683 | goto out; | |
1684 | ||
ad465cae AA |
1685 | ret = -EFAULT; |
1686 | if (copy_from_user(&uffdio_copy, user_uffdio_copy, | |
1687 | /* don't copy "copy" last field */ | |
1688 | sizeof(uffdio_copy)-sizeof(__s64))) | |
1689 | goto out; | |
1690 | ||
1691 | ret = validate_range(ctx->mm, uffdio_copy.dst, uffdio_copy.len); | |
1692 | if (ret) | |
1693 | goto out; | |
1694 | /* | |
1695 | * double check for wraparound just in case. copy_from_user() | |
1696 | * will later check uffdio_copy.src + uffdio_copy.len to fit | |
1697 | * in the userland range. | |
1698 | */ | |
1699 | ret = -EINVAL; | |
1700 | if (uffdio_copy.src + uffdio_copy.len <= uffdio_copy.src) | |
1701 | goto out; | |
1702 | if (uffdio_copy.mode & ~UFFDIO_COPY_MODE_DONTWAKE) | |
1703 | goto out; | |
d2005e3f ON |
1704 | if (mmget_not_zero(ctx->mm)) { |
1705 | ret = mcopy_atomic(ctx->mm, uffdio_copy.dst, uffdio_copy.src, | |
df2cc96e | 1706 | uffdio_copy.len, &ctx->mmap_changing); |
d2005e3f | 1707 | mmput(ctx->mm); |
96333187 | 1708 | } else { |
e86b298b | 1709 | return -ESRCH; |
d2005e3f | 1710 | } |
ad465cae AA |
1711 | if (unlikely(put_user(ret, &user_uffdio_copy->copy))) |
1712 | return -EFAULT; | |
1713 | if (ret < 0) | |
1714 | goto out; | |
1715 | BUG_ON(!ret); | |
1716 | /* len == 0 would wake all */ | |
1717 | range.len = ret; | |
1718 | if (!(uffdio_copy.mode & UFFDIO_COPY_MODE_DONTWAKE)) { | |
1719 | range.start = uffdio_copy.dst; | |
1720 | wake_userfault(ctx, &range); | |
1721 | } | |
1722 | ret = range.len == uffdio_copy.len ? 0 : -EAGAIN; | |
1723 | out: | |
1724 | return ret; | |
1725 | } | |
1726 | ||
1727 | static int userfaultfd_zeropage(struct userfaultfd_ctx *ctx, | |
1728 | unsigned long arg) | |
1729 | { | |
1730 | __s64 ret; | |
1731 | struct uffdio_zeropage uffdio_zeropage; | |
1732 | struct uffdio_zeropage __user *user_uffdio_zeropage; | |
1733 | struct userfaultfd_wake_range range; | |
1734 | ||
1735 | user_uffdio_zeropage = (struct uffdio_zeropage __user *) arg; | |
1736 | ||
df2cc96e MR |
1737 | ret = -EAGAIN; |
1738 | if (READ_ONCE(ctx->mmap_changing)) | |
1739 | goto out; | |
1740 | ||
ad465cae AA |
1741 | ret = -EFAULT; |
1742 | if (copy_from_user(&uffdio_zeropage, user_uffdio_zeropage, | |
1743 | /* don't copy "zeropage" last field */ | |
1744 | sizeof(uffdio_zeropage)-sizeof(__s64))) | |
1745 | goto out; | |
1746 | ||
1747 | ret = validate_range(ctx->mm, uffdio_zeropage.range.start, | |
1748 | uffdio_zeropage.range.len); | |
1749 | if (ret) | |
1750 | goto out; | |
1751 | ret = -EINVAL; | |
1752 | if (uffdio_zeropage.mode & ~UFFDIO_ZEROPAGE_MODE_DONTWAKE) | |
1753 | goto out; | |
1754 | ||
d2005e3f ON |
1755 | if (mmget_not_zero(ctx->mm)) { |
1756 | ret = mfill_zeropage(ctx->mm, uffdio_zeropage.range.start, | |
df2cc96e MR |
1757 | uffdio_zeropage.range.len, |
1758 | &ctx->mmap_changing); | |
d2005e3f | 1759 | mmput(ctx->mm); |
9d95aa4b | 1760 | } else { |
e86b298b | 1761 | return -ESRCH; |
d2005e3f | 1762 | } |
ad465cae AA |
1763 | if (unlikely(put_user(ret, &user_uffdio_zeropage->zeropage))) |
1764 | return -EFAULT; | |
1765 | if (ret < 0) | |
1766 | goto out; | |
1767 | /* len == 0 would wake all */ | |
1768 | BUG_ON(!ret); | |
1769 | range.len = ret; | |
1770 | if (!(uffdio_zeropage.mode & UFFDIO_ZEROPAGE_MODE_DONTWAKE)) { | |
1771 | range.start = uffdio_zeropage.range.start; | |
1772 | wake_userfault(ctx, &range); | |
1773 | } | |
1774 | ret = range.len == uffdio_zeropage.range.len ? 0 : -EAGAIN; | |
1775 | out: | |
1776 | return ret; | |
1777 | } | |
1778 | ||
9cd75c3c PE |
1779 | static inline unsigned int uffd_ctx_features(__u64 user_features) |
1780 | { | |
1781 | /* | |
1782 | * For the current set of features the bits just coincide | |
1783 | */ | |
1784 | return (unsigned int)user_features; | |
1785 | } | |
1786 | ||
86039bd3 AA |
1787 | /* |
1788 | * userland asks for a certain API version and we return which bits | |
1789 | * and ioctl commands are implemented in this kernel for such API | |
1790 | * version or -EINVAL if unknown. | |
1791 | */ | |
1792 | static int userfaultfd_api(struct userfaultfd_ctx *ctx, | |
1793 | unsigned long arg) | |
1794 | { | |
1795 | struct uffdio_api uffdio_api; | |
1796 | void __user *buf = (void __user *)arg; | |
1797 | int ret; | |
65603144 | 1798 | __u64 features; |
86039bd3 AA |
1799 | |
1800 | ret = -EINVAL; | |
1801 | if (ctx->state != UFFD_STATE_WAIT_API) | |
1802 | goto out; | |
1803 | ret = -EFAULT; | |
a9b85f94 | 1804 | if (copy_from_user(&uffdio_api, buf, sizeof(uffdio_api))) |
86039bd3 | 1805 | goto out; |
65603144 AA |
1806 | features = uffdio_api.features; |
1807 | if (uffdio_api.api != UFFD_API || (features & ~UFFD_API_FEATURES)) { | |
86039bd3 AA |
1808 | memset(&uffdio_api, 0, sizeof(uffdio_api)); |
1809 | if (copy_to_user(buf, &uffdio_api, sizeof(uffdio_api))) | |
1810 | goto out; | |
1811 | ret = -EINVAL; | |
1812 | goto out; | |
1813 | } | |
65603144 AA |
1814 | /* report all available features and ioctls to userland */ |
1815 | uffdio_api.features = UFFD_API_FEATURES; | |
86039bd3 AA |
1816 | uffdio_api.ioctls = UFFD_API_IOCTLS; |
1817 | ret = -EFAULT; | |
1818 | if (copy_to_user(buf, &uffdio_api, sizeof(uffdio_api))) | |
1819 | goto out; | |
1820 | ctx->state = UFFD_STATE_RUNNING; | |
65603144 AA |
1821 | /* only enable the requested features for this uffd context */ |
1822 | ctx->features = uffd_ctx_features(features); | |
86039bd3 AA |
1823 | ret = 0; |
1824 | out: | |
1825 | return ret; | |
1826 | } | |
1827 | ||
1828 | static long userfaultfd_ioctl(struct file *file, unsigned cmd, | |
1829 | unsigned long arg) | |
1830 | { | |
1831 | int ret = -EINVAL; | |
1832 | struct userfaultfd_ctx *ctx = file->private_data; | |
1833 | ||
e6485a47 AA |
1834 | if (cmd != UFFDIO_API && ctx->state == UFFD_STATE_WAIT_API) |
1835 | return -EINVAL; | |
1836 | ||
86039bd3 AA |
1837 | switch(cmd) { |
1838 | case UFFDIO_API: | |
1839 | ret = userfaultfd_api(ctx, arg); | |
1840 | break; | |
1841 | case UFFDIO_REGISTER: | |
1842 | ret = userfaultfd_register(ctx, arg); | |
1843 | break; | |
1844 | case UFFDIO_UNREGISTER: | |
1845 | ret = userfaultfd_unregister(ctx, arg); | |
1846 | break; | |
1847 | case UFFDIO_WAKE: | |
1848 | ret = userfaultfd_wake(ctx, arg); | |
1849 | break; | |
ad465cae AA |
1850 | case UFFDIO_COPY: |
1851 | ret = userfaultfd_copy(ctx, arg); | |
1852 | break; | |
1853 | case UFFDIO_ZEROPAGE: | |
1854 | ret = userfaultfd_zeropage(ctx, arg); | |
1855 | break; | |
86039bd3 AA |
1856 | } |
1857 | return ret; | |
1858 | } | |
1859 | ||
1860 | #ifdef CONFIG_PROC_FS | |
1861 | static void userfaultfd_show_fdinfo(struct seq_file *m, struct file *f) | |
1862 | { | |
1863 | struct userfaultfd_ctx *ctx = f->private_data; | |
ac6424b9 | 1864 | wait_queue_entry_t *wq; |
86039bd3 AA |
1865 | unsigned long pending = 0, total = 0; |
1866 | ||
15b726ef | 1867 | spin_lock(&ctx->fault_pending_wqh.lock); |
2055da97 | 1868 | list_for_each_entry(wq, &ctx->fault_pending_wqh.head, entry) { |
15b726ef AA |
1869 | pending++; |
1870 | total++; | |
1871 | } | |
2055da97 | 1872 | list_for_each_entry(wq, &ctx->fault_wqh.head, entry) { |
86039bd3 AA |
1873 | total++; |
1874 | } | |
15b726ef | 1875 | spin_unlock(&ctx->fault_pending_wqh.lock); |
86039bd3 AA |
1876 | |
1877 | /* | |
1878 | * If more protocols will be added, there will be all shown | |
1879 | * separated by a space. Like this: | |
1880 | * protocols: aa:... bb:... | |
1881 | */ | |
1882 | seq_printf(m, "pending:\t%lu\ntotal:\t%lu\nAPI:\t%Lx:%x:%Lx\n", | |
045098e9 | 1883 | pending, total, UFFD_API, ctx->features, |
86039bd3 AA |
1884 | UFFD_API_IOCTLS|UFFD_API_RANGE_IOCTLS); |
1885 | } | |
1886 | #endif | |
1887 | ||
1888 | static const struct file_operations userfaultfd_fops = { | |
1889 | #ifdef CONFIG_PROC_FS | |
1890 | .show_fdinfo = userfaultfd_show_fdinfo, | |
1891 | #endif | |
1892 | .release = userfaultfd_release, | |
1893 | .poll = userfaultfd_poll, | |
1894 | .read = userfaultfd_read, | |
1895 | .unlocked_ioctl = userfaultfd_ioctl, | |
1896 | .compat_ioctl = userfaultfd_ioctl, | |
1897 | .llseek = noop_llseek, | |
1898 | }; | |
1899 | ||
3004ec9c AA |
1900 | static void init_once_userfaultfd_ctx(void *mem) |
1901 | { | |
1902 | struct userfaultfd_ctx *ctx = (struct userfaultfd_ctx *) mem; | |
1903 | ||
1904 | init_waitqueue_head(&ctx->fault_pending_wqh); | |
1905 | init_waitqueue_head(&ctx->fault_wqh); | |
9cd75c3c | 1906 | init_waitqueue_head(&ctx->event_wqh); |
3004ec9c | 1907 | init_waitqueue_head(&ctx->fd_wqh); |
2c5b7e1b | 1908 | seqcount_init(&ctx->refile_seq); |
3004ec9c AA |
1909 | } |
1910 | ||
284cd241 | 1911 | SYSCALL_DEFINE1(userfaultfd, int, flags) |
86039bd3 | 1912 | { |
86039bd3 | 1913 | struct userfaultfd_ctx *ctx; |
284cd241 | 1914 | int fd; |
86039bd3 AA |
1915 | |
1916 | BUG_ON(!current->mm); | |
1917 | ||
1918 | /* Check the UFFD_* constants for consistency. */ | |
1919 | BUILD_BUG_ON(UFFD_CLOEXEC != O_CLOEXEC); | |
1920 | BUILD_BUG_ON(UFFD_NONBLOCK != O_NONBLOCK); | |
1921 | ||
86039bd3 | 1922 | if (flags & ~UFFD_SHARED_FCNTL_FLAGS) |
284cd241 | 1923 | return -EINVAL; |
86039bd3 | 1924 | |
3004ec9c | 1925 | ctx = kmem_cache_alloc(userfaultfd_ctx_cachep, GFP_KERNEL); |
86039bd3 | 1926 | if (!ctx) |
284cd241 | 1927 | return -ENOMEM; |
86039bd3 | 1928 | |
ca880420 | 1929 | refcount_set(&ctx->refcount, 1); |
86039bd3 | 1930 | ctx->flags = flags; |
9cd75c3c | 1931 | ctx->features = 0; |
86039bd3 AA |
1932 | ctx->state = UFFD_STATE_WAIT_API; |
1933 | ctx->released = false; | |
df2cc96e | 1934 | ctx->mmap_changing = false; |
86039bd3 AA |
1935 | ctx->mm = current->mm; |
1936 | /* prevent the mm struct to be freed */ | |
f1f10076 | 1937 | mmgrab(ctx->mm); |
86039bd3 | 1938 | |
284cd241 EB |
1939 | fd = anon_inode_getfd("[userfaultfd]", &userfaultfd_fops, ctx, |
1940 | O_RDWR | (flags & UFFD_SHARED_FCNTL_FLAGS)); | |
1941 | if (fd < 0) { | |
d2005e3f | 1942 | mmdrop(ctx->mm); |
3004ec9c | 1943 | kmem_cache_free(userfaultfd_ctx_cachep, ctx); |
c03e946f | 1944 | } |
86039bd3 | 1945 | return fd; |
86039bd3 | 1946 | } |
3004ec9c AA |
1947 | |
1948 | static int __init userfaultfd_init(void) | |
1949 | { | |
1950 | userfaultfd_ctx_cachep = kmem_cache_create("userfaultfd_ctx_cache", | |
1951 | sizeof(struct userfaultfd_ctx), | |
1952 | 0, | |
1953 | SLAB_HWCACHE_ALIGN|SLAB_PANIC, | |
1954 | init_once_userfaultfd_ctx); | |
1955 | return 0; | |
1956 | } | |
1957 | __initcall(userfaultfd_init); |