Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 1 | /* |
| 2 | * fs/userfaultfd.c |
| 3 | * |
| 4 | * Copyright (C) 2007 Davide Libenzi <davidel@xmailserver.org> |
| 5 | * Copyright (C) 2008-2009 Red Hat, Inc. |
| 6 | * Copyright (C) 2015 Red Hat, Inc. |
| 7 | * |
| 8 | * This work is licensed under the terms of the GNU GPL, version 2. See |
| 9 | * the COPYING file in the top-level directory. |
| 10 | * |
| 11 | * Some part derived from fs/eventfd.c (anon inode setup) and |
| 12 | * mm/ksm.c (mm hashing). |
| 13 | */ |
| 14 | |
Pavel Emelyanov | 9cd75c3 | 2017-02-22 15:42:21 -0800 | [diff] [blame^] | 15 | #include <linux/list.h> |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 16 | #include <linux/hashtable.h> |
| 17 | #include <linux/sched.h> |
| 18 | #include <linux/mm.h> |
| 19 | #include <linux/poll.h> |
| 20 | #include <linux/slab.h> |
| 21 | #include <linux/seq_file.h> |
| 22 | #include <linux/file.h> |
| 23 | #include <linux/bug.h> |
| 24 | #include <linux/anon_inodes.h> |
| 25 | #include <linux/syscalls.h> |
| 26 | #include <linux/userfaultfd_k.h> |
| 27 | #include <linux/mempolicy.h> |
| 28 | #include <linux/ioctl.h> |
| 29 | #include <linux/security.h> |
| 30 | |
Andrea Arcangeli | 3004ec9 | 2015-09-04 15:46:48 -0700 | [diff] [blame] | 31 | static struct kmem_cache *userfaultfd_ctx_cachep __read_mostly; |
| 32 | |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 33 | enum userfaultfd_state { |
| 34 | UFFD_STATE_WAIT_API, |
| 35 | UFFD_STATE_RUNNING, |
| 36 | }; |
| 37 | |
Andrea Arcangeli | 3004ec9 | 2015-09-04 15:46:48 -0700 | [diff] [blame] | 38 | /* |
| 39 | * Start with fault_pending_wqh and fault_wqh so they're more likely |
| 40 | * to be in the same cacheline. |
| 41 | */ |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 42 | struct userfaultfd_ctx { |
Andrea Arcangeli | 15b726e | 2015-09-04 15:46:44 -0700 | [diff] [blame] | 43 | /* waitqueue head for the pending (i.e. not read) userfaults */ |
| 44 | wait_queue_head_t fault_pending_wqh; |
| 45 | /* waitqueue head for the userfaults */ |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 46 | wait_queue_head_t fault_wqh; |
| 47 | /* waitqueue head for the pseudo fd to wakeup poll/read */ |
| 48 | wait_queue_head_t fd_wqh; |
Pavel Emelyanov | 9cd75c3 | 2017-02-22 15:42:21 -0800 | [diff] [blame^] | 49 | /* waitqueue head for events */ |
| 50 | wait_queue_head_t event_wqh; |
Andrea Arcangeli | 2c5b7e1 | 2015-09-04 15:47:23 -0700 | [diff] [blame] | 51 | /* a refile sequence protected by fault_pending_wqh lock */ |
| 52 | struct seqcount refile_seq; |
Andrea Arcangeli | 3004ec9 | 2015-09-04 15:46:48 -0700 | [diff] [blame] | 53 | /* pseudo fd refcounting */ |
| 54 | atomic_t refcount; |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 55 | /* userfaultfd syscall flags */ |
| 56 | unsigned int flags; |
Pavel Emelyanov | 9cd75c3 | 2017-02-22 15:42:21 -0800 | [diff] [blame^] | 57 | /* features requested from the userspace */ |
| 58 | unsigned int features; |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 59 | /* state machine */ |
| 60 | enum userfaultfd_state state; |
| 61 | /* released */ |
| 62 | bool released; |
| 63 | /* mm with one ore more vmas attached to this userfaultfd_ctx */ |
| 64 | struct mm_struct *mm; |
| 65 | }; |
| 66 | |
| 67 | struct userfaultfd_wait_queue { |
Andrea Arcangeli | a9b85f9 | 2015-09-04 15:46:37 -0700 | [diff] [blame] | 68 | struct uffd_msg msg; |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 69 | wait_queue_t wq; |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 70 | struct userfaultfd_ctx *ctx; |
Andrea Arcangeli | 15a77c6 | 2017-01-24 15:17:59 -0800 | [diff] [blame] | 71 | bool waken; |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 72 | }; |
| 73 | |
| 74 | struct userfaultfd_wake_range { |
| 75 | unsigned long start; |
| 76 | unsigned long len; |
| 77 | }; |
| 78 | |
| 79 | static int userfaultfd_wake_function(wait_queue_t *wq, unsigned mode, |
| 80 | int wake_flags, void *key) |
| 81 | { |
| 82 | struct userfaultfd_wake_range *range = key; |
| 83 | int ret; |
| 84 | struct userfaultfd_wait_queue *uwq; |
| 85 | unsigned long start, len; |
| 86 | |
| 87 | uwq = container_of(wq, struct userfaultfd_wait_queue, wq); |
| 88 | ret = 0; |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 89 | /* len == 0 means wake all */ |
| 90 | start = range->start; |
| 91 | len = range->len; |
Andrea Arcangeli | a9b85f9 | 2015-09-04 15:46:37 -0700 | [diff] [blame] | 92 | if (len && (start > uwq->msg.arg.pagefault.address || |
| 93 | start + len <= uwq->msg.arg.pagefault.address)) |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 94 | goto out; |
Andrea Arcangeli | 15a77c6 | 2017-01-24 15:17:59 -0800 | [diff] [blame] | 95 | WRITE_ONCE(uwq->waken, true); |
| 96 | /* |
| 97 | * The implicit smp_mb__before_spinlock in try_to_wake_up() |
| 98 | * renders uwq->waken visible to other CPUs before the task is |
| 99 | * waken. |
| 100 | */ |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 101 | ret = wake_up_state(wq->private, mode); |
| 102 | if (ret) |
| 103 | /* |
| 104 | * Wake only once, autoremove behavior. |
| 105 | * |
| 106 | * After the effect of list_del_init is visible to the |
| 107 | * other CPUs, the waitqueue may disappear from under |
| 108 | * us, see the !list_empty_careful() in |
| 109 | * handle_userfault(). try_to_wake_up() has an |
| 110 | * implicit smp_mb__before_spinlock, and the |
| 111 | * wq->private is read before calling the extern |
| 112 | * function "wake_up_state" (which in turns calls |
| 113 | * try_to_wake_up). While the spin_lock;spin_unlock; |
| 114 | * wouldn't be enough, the smp_mb__before_spinlock is |
| 115 | * enough to avoid an explicit smp_mb() here. |
| 116 | */ |
| 117 | list_del_init(&wq->task_list); |
| 118 | out: |
| 119 | return ret; |
| 120 | } |
| 121 | |
| 122 | /** |
| 123 | * userfaultfd_ctx_get - Acquires a reference to the internal userfaultfd |
| 124 | * context. |
| 125 | * @ctx: [in] Pointer to the userfaultfd context. |
| 126 | * |
| 127 | * Returns: In case of success, returns not zero. |
| 128 | */ |
| 129 | static void userfaultfd_ctx_get(struct userfaultfd_ctx *ctx) |
| 130 | { |
| 131 | if (!atomic_inc_not_zero(&ctx->refcount)) |
| 132 | BUG(); |
| 133 | } |
| 134 | |
| 135 | /** |
| 136 | * userfaultfd_ctx_put - Releases a reference to the internal userfaultfd |
| 137 | * context. |
| 138 | * @ctx: [in] Pointer to userfaultfd context. |
| 139 | * |
| 140 | * The userfaultfd context reference must have been previously acquired either |
| 141 | * with userfaultfd_ctx_get() or userfaultfd_ctx_fdget(). |
| 142 | */ |
| 143 | static void userfaultfd_ctx_put(struct userfaultfd_ctx *ctx) |
| 144 | { |
| 145 | if (atomic_dec_and_test(&ctx->refcount)) { |
| 146 | VM_BUG_ON(spin_is_locked(&ctx->fault_pending_wqh.lock)); |
| 147 | VM_BUG_ON(waitqueue_active(&ctx->fault_pending_wqh)); |
| 148 | VM_BUG_ON(spin_is_locked(&ctx->fault_wqh.lock)); |
| 149 | VM_BUG_ON(waitqueue_active(&ctx->fault_wqh)); |
Pavel Emelyanov | 9cd75c3 | 2017-02-22 15:42:21 -0800 | [diff] [blame^] | 150 | VM_BUG_ON(spin_is_locked(&ctx->event_wqh.lock)); |
| 151 | VM_BUG_ON(waitqueue_active(&ctx->event_wqh)); |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 152 | VM_BUG_ON(spin_is_locked(&ctx->fd_wqh.lock)); |
| 153 | VM_BUG_ON(waitqueue_active(&ctx->fd_wqh)); |
Oleg Nesterov | d2005e3 | 2016-05-20 16:58:36 -0700 | [diff] [blame] | 154 | mmdrop(ctx->mm); |
Andrea Arcangeli | 3004ec9 | 2015-09-04 15:46:48 -0700 | [diff] [blame] | 155 | kmem_cache_free(userfaultfd_ctx_cachep, ctx); |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 156 | } |
| 157 | } |
| 158 | |
Andrea Arcangeli | a9b85f9 | 2015-09-04 15:46:37 -0700 | [diff] [blame] | 159 | static inline void msg_init(struct uffd_msg *msg) |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 160 | { |
Andrea Arcangeli | a9b85f9 | 2015-09-04 15:46:37 -0700 | [diff] [blame] | 161 | BUILD_BUG_ON(sizeof(struct uffd_msg) != 32); |
| 162 | /* |
| 163 | * Must use memset to zero out the paddings or kernel data is |
| 164 | * leaked to userland. |
| 165 | */ |
| 166 | memset(msg, 0, sizeof(struct uffd_msg)); |
| 167 | } |
| 168 | |
| 169 | static inline struct uffd_msg userfault_msg(unsigned long address, |
| 170 | unsigned int flags, |
| 171 | unsigned long reason) |
| 172 | { |
| 173 | struct uffd_msg msg; |
| 174 | msg_init(&msg); |
| 175 | msg.event = UFFD_EVENT_PAGEFAULT; |
| 176 | msg.arg.pagefault.address = address; |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 177 | if (flags & FAULT_FLAG_WRITE) |
| 178 | /* |
Andrea Arcangeli | a4605a6 | 2017-02-22 15:42:09 -0800 | [diff] [blame] | 179 | * If UFFD_FEATURE_PAGEFAULT_FLAG_WP was set in the |
Andrea Arcangeli | a9b85f9 | 2015-09-04 15:46:37 -0700 | [diff] [blame] | 180 | * uffdio_api.features and UFFD_PAGEFAULT_FLAG_WRITE |
| 181 | * was not set in a UFFD_EVENT_PAGEFAULT, it means it |
| 182 | * was a read fault, otherwise if set it means it's |
| 183 | * a write fault. |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 184 | */ |
Andrea Arcangeli | a9b85f9 | 2015-09-04 15:46:37 -0700 | [diff] [blame] | 185 | msg.arg.pagefault.flags |= UFFD_PAGEFAULT_FLAG_WRITE; |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 186 | if (reason & VM_UFFD_WP) |
| 187 | /* |
Andrea Arcangeli | a9b85f9 | 2015-09-04 15:46:37 -0700 | [diff] [blame] | 188 | * If UFFD_FEATURE_PAGEFAULT_FLAG_WP was set in the |
| 189 | * uffdio_api.features and UFFD_PAGEFAULT_FLAG_WP was |
| 190 | * not set in a UFFD_EVENT_PAGEFAULT, it means it was |
| 191 | * a missing fault, otherwise if set it means it's a |
| 192 | * write protect fault. |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 193 | */ |
Andrea Arcangeli | a9b85f9 | 2015-09-04 15:46:37 -0700 | [diff] [blame] | 194 | msg.arg.pagefault.flags |= UFFD_PAGEFAULT_FLAG_WP; |
| 195 | return msg; |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 196 | } |
| 197 | |
| 198 | /* |
Andrea Arcangeli | 8d2afd9 | 2015-09-04 15:46:51 -0700 | [diff] [blame] | 199 | * Verify the pagetables are still not ok after having reigstered into |
| 200 | * the fault_pending_wqh to avoid userland having to UFFDIO_WAKE any |
| 201 | * userfault that has already been resolved, if userfaultfd_read and |
| 202 | * UFFDIO_COPY|ZEROPAGE are being run simultaneously on two different |
| 203 | * threads. |
| 204 | */ |
| 205 | static inline bool userfaultfd_must_wait(struct userfaultfd_ctx *ctx, |
| 206 | unsigned long address, |
| 207 | unsigned long flags, |
| 208 | unsigned long reason) |
| 209 | { |
| 210 | struct mm_struct *mm = ctx->mm; |
| 211 | pgd_t *pgd; |
| 212 | pud_t *pud; |
| 213 | pmd_t *pmd, _pmd; |
| 214 | pte_t *pte; |
| 215 | bool ret = true; |
| 216 | |
| 217 | VM_BUG_ON(!rwsem_is_locked(&mm->mmap_sem)); |
| 218 | |
| 219 | pgd = pgd_offset(mm, address); |
| 220 | if (!pgd_present(*pgd)) |
| 221 | goto out; |
| 222 | pud = pud_offset(pgd, address); |
| 223 | if (!pud_present(*pud)) |
| 224 | goto out; |
| 225 | pmd = pmd_offset(pud, address); |
| 226 | /* |
| 227 | * READ_ONCE must function as a barrier with narrower scope |
| 228 | * and it must be equivalent to: |
| 229 | * _pmd = *pmd; barrier(); |
| 230 | * |
| 231 | * This is to deal with the instability (as in |
| 232 | * pmd_trans_unstable) of the pmd. |
| 233 | */ |
| 234 | _pmd = READ_ONCE(*pmd); |
| 235 | if (!pmd_present(_pmd)) |
| 236 | goto out; |
| 237 | |
| 238 | ret = false; |
| 239 | if (pmd_trans_huge(_pmd)) |
| 240 | goto out; |
| 241 | |
| 242 | /* |
| 243 | * the pmd is stable (as in !pmd_trans_unstable) so we can re-read it |
| 244 | * and use the standard pte_offset_map() instead of parsing _pmd. |
| 245 | */ |
| 246 | pte = pte_offset_map(pmd, address); |
| 247 | /* |
| 248 | * Lockless access: we're in a wait_event so it's ok if it |
| 249 | * changes under us. |
| 250 | */ |
| 251 | if (pte_none(*pte)) |
| 252 | ret = true; |
| 253 | pte_unmap(pte); |
| 254 | |
| 255 | out: |
| 256 | return ret; |
| 257 | } |
| 258 | |
| 259 | /* |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 260 | * The locking rules involved in returning VM_FAULT_RETRY depending on |
| 261 | * FAULT_FLAG_ALLOW_RETRY, FAULT_FLAG_RETRY_NOWAIT and |
| 262 | * FAULT_FLAG_KILLABLE are not straightforward. The "Caution" |
| 263 | * recommendation in __lock_page_or_retry is not an understatement. |
| 264 | * |
| 265 | * If FAULT_FLAG_ALLOW_RETRY is set, the mmap_sem must be released |
| 266 | * before returning VM_FAULT_RETRY only if FAULT_FLAG_RETRY_NOWAIT is |
| 267 | * not set. |
| 268 | * |
| 269 | * If FAULT_FLAG_ALLOW_RETRY is set but FAULT_FLAG_KILLABLE is not |
| 270 | * set, VM_FAULT_RETRY can still be returned if and only if there are |
| 271 | * fatal_signal_pending()s, and the mmap_sem must be released before |
| 272 | * returning it. |
| 273 | */ |
Jan Kara | 82b0f8c | 2016-12-14 15:06:58 -0800 | [diff] [blame] | 274 | int handle_userfault(struct vm_fault *vmf, unsigned long reason) |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 275 | { |
Jan Kara | 82b0f8c | 2016-12-14 15:06:58 -0800 | [diff] [blame] | 276 | struct mm_struct *mm = vmf->vma->vm_mm; |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 277 | struct userfaultfd_ctx *ctx; |
| 278 | struct userfaultfd_wait_queue uwq; |
Andrea Arcangeli | ba85c70 | 2015-09-04 15:46:41 -0700 | [diff] [blame] | 279 | int ret; |
Andrea Arcangeli | dfa37dc | 2015-09-04 15:47:18 -0700 | [diff] [blame] | 280 | bool must_wait, return_to_userland; |
Andrea Arcangeli | 15a77c6 | 2017-01-24 15:17:59 -0800 | [diff] [blame] | 281 | long blocking_state; |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 282 | |
| 283 | BUG_ON(!rwsem_is_locked(&mm->mmap_sem)); |
| 284 | |
Andrea Arcangeli | ba85c70 | 2015-09-04 15:46:41 -0700 | [diff] [blame] | 285 | ret = VM_FAULT_SIGBUS; |
Jan Kara | 82b0f8c | 2016-12-14 15:06:58 -0800 | [diff] [blame] | 286 | ctx = vmf->vma->vm_userfaultfd_ctx.ctx; |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 287 | if (!ctx) |
Andrea Arcangeli | ba85c70 | 2015-09-04 15:46:41 -0700 | [diff] [blame] | 288 | goto out; |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 289 | |
| 290 | BUG_ON(ctx->mm != mm); |
| 291 | |
| 292 | VM_BUG_ON(reason & ~(VM_UFFD_MISSING|VM_UFFD_WP)); |
| 293 | VM_BUG_ON(!(reason & VM_UFFD_MISSING) ^ !!(reason & VM_UFFD_WP)); |
| 294 | |
| 295 | /* |
| 296 | * If it's already released don't get it. This avoids to loop |
| 297 | * in __get_user_pages if userfaultfd_release waits on the |
| 298 | * caller of handle_userfault to release the mmap_sem. |
| 299 | */ |
| 300 | if (unlikely(ACCESS_ONCE(ctx->released))) |
Andrea Arcangeli | ba85c70 | 2015-09-04 15:46:41 -0700 | [diff] [blame] | 301 | goto out; |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 302 | |
| 303 | /* |
Linus Torvalds | 39680f5 | 2016-03-01 11:56:22 -0800 | [diff] [blame] | 304 | * We don't do userfault handling for the final child pid update. |
| 305 | */ |
| 306 | if (current->flags & PF_EXITING) |
| 307 | goto out; |
| 308 | |
| 309 | /* |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 310 | * Check that we can return VM_FAULT_RETRY. |
| 311 | * |
| 312 | * NOTE: it should become possible to return VM_FAULT_RETRY |
| 313 | * even if FAULT_FLAG_TRIED is set without leading to gup() |
| 314 | * -EBUSY failures, if the userfaultfd is to be extended for |
| 315 | * VM_UFFD_WP tracking and we intend to arm the userfault |
| 316 | * without first stopping userland access to the memory. For |
| 317 | * VM_UFFD_MISSING userfaults this is enough for now. |
| 318 | */ |
Jan Kara | 82b0f8c | 2016-12-14 15:06:58 -0800 | [diff] [blame] | 319 | if (unlikely(!(vmf->flags & FAULT_FLAG_ALLOW_RETRY))) { |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 320 | /* |
| 321 | * Validate the invariant that nowait must allow retry |
| 322 | * to be sure not to return SIGBUS erroneously on |
| 323 | * nowait invocations. |
| 324 | */ |
Jan Kara | 82b0f8c | 2016-12-14 15:06:58 -0800 | [diff] [blame] | 325 | BUG_ON(vmf->flags & FAULT_FLAG_RETRY_NOWAIT); |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 326 | #ifdef CONFIG_DEBUG_VM |
| 327 | if (printk_ratelimit()) { |
| 328 | printk(KERN_WARNING |
Jan Kara | 82b0f8c | 2016-12-14 15:06:58 -0800 | [diff] [blame] | 329 | "FAULT_FLAG_ALLOW_RETRY missing %x\n", |
| 330 | vmf->flags); |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 331 | dump_stack(); |
| 332 | } |
| 333 | #endif |
Andrea Arcangeli | ba85c70 | 2015-09-04 15:46:41 -0700 | [diff] [blame] | 334 | goto out; |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 335 | } |
| 336 | |
| 337 | /* |
| 338 | * Handle nowait, not much to do other than tell it to retry |
| 339 | * and wait. |
| 340 | */ |
Andrea Arcangeli | ba85c70 | 2015-09-04 15:46:41 -0700 | [diff] [blame] | 341 | ret = VM_FAULT_RETRY; |
Jan Kara | 82b0f8c | 2016-12-14 15:06:58 -0800 | [diff] [blame] | 342 | if (vmf->flags & FAULT_FLAG_RETRY_NOWAIT) |
Andrea Arcangeli | ba85c70 | 2015-09-04 15:46:41 -0700 | [diff] [blame] | 343 | goto out; |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 344 | |
| 345 | /* take the reference before dropping the mmap_sem */ |
| 346 | userfaultfd_ctx_get(ctx); |
| 347 | |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 348 | init_waitqueue_func_entry(&uwq.wq, userfaultfd_wake_function); |
| 349 | uwq.wq.private = current; |
Jan Kara | 82b0f8c | 2016-12-14 15:06:58 -0800 | [diff] [blame] | 350 | uwq.msg = userfault_msg(vmf->address, vmf->flags, reason); |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 351 | uwq.ctx = ctx; |
Andrea Arcangeli | 15a77c6 | 2017-01-24 15:17:59 -0800 | [diff] [blame] | 352 | uwq.waken = false; |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 353 | |
Kirill A. Shutemov | bae473a | 2016-07-26 15:25:20 -0700 | [diff] [blame] | 354 | return_to_userland = |
Jan Kara | 82b0f8c | 2016-12-14 15:06:58 -0800 | [diff] [blame] | 355 | (vmf->flags & (FAULT_FLAG_USER|FAULT_FLAG_KILLABLE)) == |
Andrea Arcangeli | dfa37dc | 2015-09-04 15:47:18 -0700 | [diff] [blame] | 356 | (FAULT_FLAG_USER|FAULT_FLAG_KILLABLE); |
Andrea Arcangeli | 15a77c6 | 2017-01-24 15:17:59 -0800 | [diff] [blame] | 357 | blocking_state = return_to_userland ? TASK_INTERRUPTIBLE : |
| 358 | TASK_KILLABLE; |
Andrea Arcangeli | dfa37dc | 2015-09-04 15:47:18 -0700 | [diff] [blame] | 359 | |
Andrea Arcangeli | 15b726e | 2015-09-04 15:46:44 -0700 | [diff] [blame] | 360 | spin_lock(&ctx->fault_pending_wqh.lock); |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 361 | /* |
| 362 | * After the __add_wait_queue the uwq is visible to userland |
| 363 | * through poll/read(). |
| 364 | */ |
Andrea Arcangeli | 15b726e | 2015-09-04 15:46:44 -0700 | [diff] [blame] | 365 | __add_wait_queue(&ctx->fault_pending_wqh, &uwq.wq); |
| 366 | /* |
| 367 | * The smp_mb() after __set_current_state prevents the reads |
| 368 | * following the spin_unlock to happen before the list_add in |
| 369 | * __add_wait_queue. |
| 370 | */ |
Andrea Arcangeli | 15a77c6 | 2017-01-24 15:17:59 -0800 | [diff] [blame] | 371 | set_current_state(blocking_state); |
Andrea Arcangeli | 15b726e | 2015-09-04 15:46:44 -0700 | [diff] [blame] | 372 | spin_unlock(&ctx->fault_pending_wqh.lock); |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 373 | |
Jan Kara | 82b0f8c | 2016-12-14 15:06:58 -0800 | [diff] [blame] | 374 | must_wait = userfaultfd_must_wait(ctx, vmf->address, vmf->flags, |
| 375 | reason); |
Andrea Arcangeli | 8d2afd9 | 2015-09-04 15:46:51 -0700 | [diff] [blame] | 376 | up_read(&mm->mmap_sem); |
| 377 | |
| 378 | if (likely(must_wait && !ACCESS_ONCE(ctx->released) && |
Andrea Arcangeli | dfa37dc | 2015-09-04 15:47:18 -0700 | [diff] [blame] | 379 | (return_to_userland ? !signal_pending(current) : |
| 380 | !fatal_signal_pending(current)))) { |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 381 | wake_up_poll(&ctx->fd_wqh, POLLIN); |
| 382 | schedule(); |
Andrea Arcangeli | ba85c70 | 2015-09-04 15:46:41 -0700 | [diff] [blame] | 383 | ret |= VM_FAULT_MAJOR; |
Andrea Arcangeli | 15a77c6 | 2017-01-24 15:17:59 -0800 | [diff] [blame] | 384 | |
| 385 | /* |
| 386 | * False wakeups can orginate even from rwsem before |
| 387 | * up_read() however userfaults will wait either for a |
| 388 | * targeted wakeup on the specific uwq waitqueue from |
| 389 | * wake_userfault() or for signals or for uffd |
| 390 | * release. |
| 391 | */ |
| 392 | while (!READ_ONCE(uwq.waken)) { |
| 393 | /* |
| 394 | * This needs the full smp_store_mb() |
| 395 | * guarantee as the state write must be |
| 396 | * visible to other CPUs before reading |
| 397 | * uwq.waken from other CPUs. |
| 398 | */ |
| 399 | set_current_state(blocking_state); |
| 400 | if (READ_ONCE(uwq.waken) || |
| 401 | READ_ONCE(ctx->released) || |
| 402 | (return_to_userland ? signal_pending(current) : |
| 403 | fatal_signal_pending(current))) |
| 404 | break; |
| 405 | schedule(); |
| 406 | } |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 407 | } |
Andrea Arcangeli | ba85c70 | 2015-09-04 15:46:41 -0700 | [diff] [blame] | 408 | |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 409 | __set_current_state(TASK_RUNNING); |
Andrea Arcangeli | 15b726e | 2015-09-04 15:46:44 -0700 | [diff] [blame] | 410 | |
Andrea Arcangeli | dfa37dc | 2015-09-04 15:47:18 -0700 | [diff] [blame] | 411 | if (return_to_userland) { |
| 412 | if (signal_pending(current) && |
| 413 | !fatal_signal_pending(current)) { |
| 414 | /* |
| 415 | * If we got a SIGSTOP or SIGCONT and this is |
| 416 | * a normal userland page fault, just let |
| 417 | * userland return so the signal will be |
| 418 | * handled and gdb debugging works. The page |
| 419 | * fault code immediately after we return from |
| 420 | * this function is going to release the |
| 421 | * mmap_sem and it's not depending on it |
| 422 | * (unlike gup would if we were not to return |
| 423 | * VM_FAULT_RETRY). |
| 424 | * |
| 425 | * If a fatal signal is pending we still take |
| 426 | * the streamlined VM_FAULT_RETRY failure path |
| 427 | * and there's no need to retake the mmap_sem |
| 428 | * in such case. |
| 429 | */ |
| 430 | down_read(&mm->mmap_sem); |
| 431 | ret = 0; |
| 432 | } |
| 433 | } |
| 434 | |
Andrea Arcangeli | 15b726e | 2015-09-04 15:46:44 -0700 | [diff] [blame] | 435 | /* |
| 436 | * Here we race with the list_del; list_add in |
| 437 | * userfaultfd_ctx_read(), however because we don't ever run |
| 438 | * list_del_init() to refile across the two lists, the prev |
| 439 | * and next pointers will never point to self. list_add also |
| 440 | * would never let any of the two pointers to point to |
| 441 | * self. So list_empty_careful won't risk to see both pointers |
| 442 | * pointing to self at any time during the list refile. The |
| 443 | * only case where list_del_init() is called is the full |
| 444 | * removal in the wake function and there we don't re-list_add |
| 445 | * and it's fine not to block on the spinlock. The uwq on this |
| 446 | * kernel stack can be released after the list_del_init. |
| 447 | */ |
Andrea Arcangeli | ba85c70 | 2015-09-04 15:46:41 -0700 | [diff] [blame] | 448 | if (!list_empty_careful(&uwq.wq.task_list)) { |
Andrea Arcangeli | 15b726e | 2015-09-04 15:46:44 -0700 | [diff] [blame] | 449 | spin_lock(&ctx->fault_pending_wqh.lock); |
| 450 | /* |
| 451 | * No need of list_del_init(), the uwq on the stack |
| 452 | * will be freed shortly anyway. |
| 453 | */ |
| 454 | list_del(&uwq.wq.task_list); |
| 455 | spin_unlock(&ctx->fault_pending_wqh.lock); |
Andrea Arcangeli | ba85c70 | 2015-09-04 15:46:41 -0700 | [diff] [blame] | 456 | } |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 457 | |
| 458 | /* |
| 459 | * ctx may go away after this if the userfault pseudo fd is |
| 460 | * already released. |
| 461 | */ |
| 462 | userfaultfd_ctx_put(ctx); |
| 463 | |
Andrea Arcangeli | ba85c70 | 2015-09-04 15:46:41 -0700 | [diff] [blame] | 464 | out: |
| 465 | return ret; |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 466 | } |
| 467 | |
Pavel Emelyanov | 9cd75c3 | 2017-02-22 15:42:21 -0800 | [diff] [blame^] | 468 | static int __maybe_unused userfaultfd_event_wait_completion( |
| 469 | struct userfaultfd_ctx *ctx, |
| 470 | struct userfaultfd_wait_queue *ewq) |
| 471 | { |
| 472 | int ret = 0; |
| 473 | |
| 474 | ewq->ctx = ctx; |
| 475 | init_waitqueue_entry(&ewq->wq, current); |
| 476 | |
| 477 | spin_lock(&ctx->event_wqh.lock); |
| 478 | /* |
| 479 | * After the __add_wait_queue the uwq is visible to userland |
| 480 | * through poll/read(). |
| 481 | */ |
| 482 | __add_wait_queue(&ctx->event_wqh, &ewq->wq); |
| 483 | for (;;) { |
| 484 | set_current_state(TASK_KILLABLE); |
| 485 | if (ewq->msg.event == 0) |
| 486 | break; |
| 487 | if (ACCESS_ONCE(ctx->released) || |
| 488 | fatal_signal_pending(current)) { |
| 489 | ret = -1; |
| 490 | __remove_wait_queue(&ctx->event_wqh, &ewq->wq); |
| 491 | break; |
| 492 | } |
| 493 | |
| 494 | spin_unlock(&ctx->event_wqh.lock); |
| 495 | |
| 496 | wake_up_poll(&ctx->fd_wqh, POLLIN); |
| 497 | schedule(); |
| 498 | |
| 499 | spin_lock(&ctx->event_wqh.lock); |
| 500 | } |
| 501 | __set_current_state(TASK_RUNNING); |
| 502 | spin_unlock(&ctx->event_wqh.lock); |
| 503 | |
| 504 | /* |
| 505 | * ctx may go away after this if the userfault pseudo fd is |
| 506 | * already released. |
| 507 | */ |
| 508 | |
| 509 | userfaultfd_ctx_put(ctx); |
| 510 | return ret; |
| 511 | } |
| 512 | |
| 513 | static void userfaultfd_event_complete(struct userfaultfd_ctx *ctx, |
| 514 | struct userfaultfd_wait_queue *ewq) |
| 515 | { |
| 516 | ewq->msg.event = 0; |
| 517 | wake_up_locked(&ctx->event_wqh); |
| 518 | __remove_wait_queue(&ctx->event_wqh, &ewq->wq); |
| 519 | } |
| 520 | |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 521 | static int userfaultfd_release(struct inode *inode, struct file *file) |
| 522 | { |
| 523 | struct userfaultfd_ctx *ctx = file->private_data; |
| 524 | struct mm_struct *mm = ctx->mm; |
| 525 | struct vm_area_struct *vma, *prev; |
| 526 | /* len == 0 means wake all */ |
| 527 | struct userfaultfd_wake_range range = { .len = 0, }; |
| 528 | unsigned long new_flags; |
| 529 | |
| 530 | ACCESS_ONCE(ctx->released) = true; |
| 531 | |
Oleg Nesterov | d2005e3 | 2016-05-20 16:58:36 -0700 | [diff] [blame] | 532 | if (!mmget_not_zero(mm)) |
| 533 | goto wakeup; |
| 534 | |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 535 | /* |
| 536 | * Flush page faults out of all CPUs. NOTE: all page faults |
| 537 | * must be retried without returning VM_FAULT_SIGBUS if |
| 538 | * userfaultfd_ctx_get() succeeds but vma->vma_userfault_ctx |
| 539 | * changes while handle_userfault released the mmap_sem. So |
| 540 | * it's critical that released is set to true (above), before |
| 541 | * taking the mmap_sem for writing. |
| 542 | */ |
| 543 | down_write(&mm->mmap_sem); |
| 544 | prev = NULL; |
| 545 | for (vma = mm->mmap; vma; vma = vma->vm_next) { |
| 546 | cond_resched(); |
| 547 | BUG_ON(!!vma->vm_userfaultfd_ctx.ctx ^ |
| 548 | !!(vma->vm_flags & (VM_UFFD_MISSING | VM_UFFD_WP))); |
| 549 | if (vma->vm_userfaultfd_ctx.ctx != ctx) { |
| 550 | prev = vma; |
| 551 | continue; |
| 552 | } |
| 553 | new_flags = vma->vm_flags & ~(VM_UFFD_MISSING | VM_UFFD_WP); |
| 554 | prev = vma_merge(mm, prev, vma->vm_start, vma->vm_end, |
| 555 | new_flags, vma->anon_vma, |
| 556 | vma->vm_file, vma->vm_pgoff, |
| 557 | vma_policy(vma), |
| 558 | NULL_VM_UFFD_CTX); |
| 559 | if (prev) |
| 560 | vma = prev; |
| 561 | else |
| 562 | prev = vma; |
| 563 | vma->vm_flags = new_flags; |
| 564 | vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX; |
| 565 | } |
| 566 | up_write(&mm->mmap_sem); |
Oleg Nesterov | d2005e3 | 2016-05-20 16:58:36 -0700 | [diff] [blame] | 567 | mmput(mm); |
| 568 | wakeup: |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 569 | /* |
Andrea Arcangeli | 15b726e | 2015-09-04 15:46:44 -0700 | [diff] [blame] | 570 | * After no new page faults can wait on this fault_*wqh, flush |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 571 | * the last page faults that may have been already waiting on |
Andrea Arcangeli | 15b726e | 2015-09-04 15:46:44 -0700 | [diff] [blame] | 572 | * the fault_*wqh. |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 573 | */ |
Andrea Arcangeli | 15b726e | 2015-09-04 15:46:44 -0700 | [diff] [blame] | 574 | spin_lock(&ctx->fault_pending_wqh.lock); |
Andrea Arcangeli | ac5be6b | 2015-09-22 14:58:49 -0700 | [diff] [blame] | 575 | __wake_up_locked_key(&ctx->fault_pending_wqh, TASK_NORMAL, &range); |
| 576 | __wake_up_locked_key(&ctx->fault_wqh, TASK_NORMAL, &range); |
Andrea Arcangeli | 15b726e | 2015-09-04 15:46:44 -0700 | [diff] [blame] | 577 | spin_unlock(&ctx->fault_pending_wqh.lock); |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 578 | |
| 579 | wake_up_poll(&ctx->fd_wqh, POLLHUP); |
| 580 | userfaultfd_ctx_put(ctx); |
| 581 | return 0; |
| 582 | } |
| 583 | |
Andrea Arcangeli | 15b726e | 2015-09-04 15:46:44 -0700 | [diff] [blame] | 584 | /* fault_pending_wqh.lock must be hold by the caller */ |
Pavel Emelyanov | 6dcc27f | 2017-02-22 15:42:18 -0800 | [diff] [blame] | 585 | static inline struct userfaultfd_wait_queue *find_userfault_in( |
| 586 | wait_queue_head_t *wqh) |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 587 | { |
| 588 | wait_queue_t *wq; |
Andrea Arcangeli | 15b726e | 2015-09-04 15:46:44 -0700 | [diff] [blame] | 589 | struct userfaultfd_wait_queue *uwq; |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 590 | |
Pavel Emelyanov | 6dcc27f | 2017-02-22 15:42:18 -0800 | [diff] [blame] | 591 | VM_BUG_ON(!spin_is_locked(&wqh->lock)); |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 592 | |
Andrea Arcangeli | 15b726e | 2015-09-04 15:46:44 -0700 | [diff] [blame] | 593 | uwq = NULL; |
Pavel Emelyanov | 6dcc27f | 2017-02-22 15:42:18 -0800 | [diff] [blame] | 594 | if (!waitqueue_active(wqh)) |
Andrea Arcangeli | 15b726e | 2015-09-04 15:46:44 -0700 | [diff] [blame] | 595 | goto out; |
| 596 | /* walk in reverse to provide FIFO behavior to read userfaults */ |
Pavel Emelyanov | 6dcc27f | 2017-02-22 15:42:18 -0800 | [diff] [blame] | 597 | wq = list_last_entry(&wqh->task_list, typeof(*wq), task_list); |
Andrea Arcangeli | 15b726e | 2015-09-04 15:46:44 -0700 | [diff] [blame] | 598 | uwq = container_of(wq, struct userfaultfd_wait_queue, wq); |
| 599 | out: |
| 600 | return uwq; |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 601 | } |
| 602 | |
Pavel Emelyanov | 6dcc27f | 2017-02-22 15:42:18 -0800 | [diff] [blame] | 603 | static inline struct userfaultfd_wait_queue *find_userfault( |
| 604 | struct userfaultfd_ctx *ctx) |
| 605 | { |
| 606 | return find_userfault_in(&ctx->fault_pending_wqh); |
| 607 | } |
| 608 | |
Pavel Emelyanov | 9cd75c3 | 2017-02-22 15:42:21 -0800 | [diff] [blame^] | 609 | static inline struct userfaultfd_wait_queue *find_userfault_evt( |
| 610 | struct userfaultfd_ctx *ctx) |
| 611 | { |
| 612 | return find_userfault_in(&ctx->event_wqh); |
| 613 | } |
| 614 | |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 615 | static unsigned int userfaultfd_poll(struct file *file, poll_table *wait) |
| 616 | { |
| 617 | struct userfaultfd_ctx *ctx = file->private_data; |
| 618 | unsigned int ret; |
| 619 | |
| 620 | poll_wait(file, &ctx->fd_wqh, wait); |
| 621 | |
| 622 | switch (ctx->state) { |
| 623 | case UFFD_STATE_WAIT_API: |
| 624 | return POLLERR; |
| 625 | case UFFD_STATE_RUNNING: |
Andrea Arcangeli | ba85c70 | 2015-09-04 15:46:41 -0700 | [diff] [blame] | 626 | /* |
| 627 | * poll() never guarantees that read won't block. |
| 628 | * userfaults can be waken before they're read(). |
| 629 | */ |
| 630 | if (unlikely(!(file->f_flags & O_NONBLOCK))) |
| 631 | return POLLERR; |
Andrea Arcangeli | 15b726e | 2015-09-04 15:46:44 -0700 | [diff] [blame] | 632 | /* |
| 633 | * lockless access to see if there are pending faults |
| 634 | * __pollwait last action is the add_wait_queue but |
| 635 | * the spin_unlock would allow the waitqueue_active to |
| 636 | * pass above the actual list_add inside |
| 637 | * add_wait_queue critical section. So use a full |
| 638 | * memory barrier to serialize the list_add write of |
| 639 | * add_wait_queue() with the waitqueue_active read |
| 640 | * below. |
| 641 | */ |
| 642 | ret = 0; |
| 643 | smp_mb(); |
| 644 | if (waitqueue_active(&ctx->fault_pending_wqh)) |
| 645 | ret = POLLIN; |
Pavel Emelyanov | 9cd75c3 | 2017-02-22 15:42:21 -0800 | [diff] [blame^] | 646 | else if (waitqueue_active(&ctx->event_wqh)) |
| 647 | ret = POLLIN; |
| 648 | |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 649 | return ret; |
| 650 | default: |
Andrea Arcangeli | 8474901 | 2017-02-22 15:42:12 -0800 | [diff] [blame] | 651 | WARN_ON_ONCE(1); |
| 652 | return POLLERR; |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 653 | } |
| 654 | } |
| 655 | |
| 656 | static ssize_t userfaultfd_ctx_read(struct userfaultfd_ctx *ctx, int no_wait, |
Andrea Arcangeli | a9b85f9 | 2015-09-04 15:46:37 -0700 | [diff] [blame] | 657 | struct uffd_msg *msg) |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 658 | { |
| 659 | ssize_t ret; |
| 660 | DECLARE_WAITQUEUE(wait, current); |
Andrea Arcangeli | 15b726e | 2015-09-04 15:46:44 -0700 | [diff] [blame] | 661 | struct userfaultfd_wait_queue *uwq; |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 662 | |
Andrea Arcangeli | 15b726e | 2015-09-04 15:46:44 -0700 | [diff] [blame] | 663 | /* always take the fd_wqh lock before the fault_pending_wqh lock */ |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 664 | spin_lock(&ctx->fd_wqh.lock); |
| 665 | __add_wait_queue(&ctx->fd_wqh, &wait); |
| 666 | for (;;) { |
| 667 | set_current_state(TASK_INTERRUPTIBLE); |
Andrea Arcangeli | 15b726e | 2015-09-04 15:46:44 -0700 | [diff] [blame] | 668 | spin_lock(&ctx->fault_pending_wqh.lock); |
| 669 | uwq = find_userfault(ctx); |
| 670 | if (uwq) { |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 671 | /* |
Andrea Arcangeli | 2c5b7e1 | 2015-09-04 15:47:23 -0700 | [diff] [blame] | 672 | * Use a seqcount to repeat the lockless check |
| 673 | * in wake_userfault() to avoid missing |
| 674 | * wakeups because during the refile both |
| 675 | * waitqueue could become empty if this is the |
| 676 | * only userfault. |
| 677 | */ |
| 678 | write_seqcount_begin(&ctx->refile_seq); |
| 679 | |
| 680 | /* |
Andrea Arcangeli | 15b726e | 2015-09-04 15:46:44 -0700 | [diff] [blame] | 681 | * The fault_pending_wqh.lock prevents the uwq |
| 682 | * to disappear from under us. |
| 683 | * |
| 684 | * Refile this userfault from |
| 685 | * fault_pending_wqh to fault_wqh, it's not |
| 686 | * pending anymore after we read it. |
| 687 | * |
| 688 | * Use list_del() by hand (as |
| 689 | * userfaultfd_wake_function also uses |
| 690 | * list_del_init() by hand) to be sure nobody |
| 691 | * changes __remove_wait_queue() to use |
| 692 | * list_del_init() in turn breaking the |
| 693 | * !list_empty_careful() check in |
| 694 | * handle_userfault(). The uwq->wq.task_list |
| 695 | * must never be empty at any time during the |
| 696 | * refile, or the waitqueue could disappear |
| 697 | * from under us. The "wait_queue_head_t" |
| 698 | * parameter of __remove_wait_queue() is unused |
| 699 | * anyway. |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 700 | */ |
Andrea Arcangeli | 15b726e | 2015-09-04 15:46:44 -0700 | [diff] [blame] | 701 | list_del(&uwq->wq.task_list); |
| 702 | __add_wait_queue(&ctx->fault_wqh, &uwq->wq); |
| 703 | |
Andrea Arcangeli | 2c5b7e1 | 2015-09-04 15:47:23 -0700 | [diff] [blame] | 704 | write_seqcount_end(&ctx->refile_seq); |
| 705 | |
Andrea Arcangeli | a9b85f9 | 2015-09-04 15:46:37 -0700 | [diff] [blame] | 706 | /* careful to always initialize msg if ret == 0 */ |
| 707 | *msg = uwq->msg; |
Andrea Arcangeli | 15b726e | 2015-09-04 15:46:44 -0700 | [diff] [blame] | 708 | spin_unlock(&ctx->fault_pending_wqh.lock); |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 709 | ret = 0; |
| 710 | break; |
| 711 | } |
Andrea Arcangeli | 15b726e | 2015-09-04 15:46:44 -0700 | [diff] [blame] | 712 | spin_unlock(&ctx->fault_pending_wqh.lock); |
Pavel Emelyanov | 9cd75c3 | 2017-02-22 15:42:21 -0800 | [diff] [blame^] | 713 | |
| 714 | spin_lock(&ctx->event_wqh.lock); |
| 715 | uwq = find_userfault_evt(ctx); |
| 716 | if (uwq) { |
| 717 | *msg = uwq->msg; |
| 718 | |
| 719 | userfaultfd_event_complete(ctx, uwq); |
| 720 | spin_unlock(&ctx->event_wqh.lock); |
| 721 | ret = 0; |
| 722 | break; |
| 723 | } |
| 724 | spin_unlock(&ctx->event_wqh.lock); |
| 725 | |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 726 | if (signal_pending(current)) { |
| 727 | ret = -ERESTARTSYS; |
| 728 | break; |
| 729 | } |
| 730 | if (no_wait) { |
| 731 | ret = -EAGAIN; |
| 732 | break; |
| 733 | } |
| 734 | spin_unlock(&ctx->fd_wqh.lock); |
| 735 | schedule(); |
| 736 | spin_lock(&ctx->fd_wqh.lock); |
| 737 | } |
| 738 | __remove_wait_queue(&ctx->fd_wqh, &wait); |
| 739 | __set_current_state(TASK_RUNNING); |
| 740 | spin_unlock(&ctx->fd_wqh.lock); |
| 741 | |
| 742 | return ret; |
| 743 | } |
| 744 | |
| 745 | static ssize_t userfaultfd_read(struct file *file, char __user *buf, |
| 746 | size_t count, loff_t *ppos) |
| 747 | { |
| 748 | struct userfaultfd_ctx *ctx = file->private_data; |
| 749 | ssize_t _ret, ret = 0; |
Andrea Arcangeli | a9b85f9 | 2015-09-04 15:46:37 -0700 | [diff] [blame] | 750 | struct uffd_msg msg; |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 751 | int no_wait = file->f_flags & O_NONBLOCK; |
| 752 | |
| 753 | if (ctx->state == UFFD_STATE_WAIT_API) |
| 754 | return -EINVAL; |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 755 | |
| 756 | for (;;) { |
Andrea Arcangeli | a9b85f9 | 2015-09-04 15:46:37 -0700 | [diff] [blame] | 757 | if (count < sizeof(msg)) |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 758 | return ret ? ret : -EINVAL; |
Andrea Arcangeli | a9b85f9 | 2015-09-04 15:46:37 -0700 | [diff] [blame] | 759 | _ret = userfaultfd_ctx_read(ctx, no_wait, &msg); |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 760 | if (_ret < 0) |
| 761 | return ret ? ret : _ret; |
Andrea Arcangeli | a9b85f9 | 2015-09-04 15:46:37 -0700 | [diff] [blame] | 762 | if (copy_to_user((__u64 __user *) buf, &msg, sizeof(msg))) |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 763 | return ret ? ret : -EFAULT; |
Andrea Arcangeli | a9b85f9 | 2015-09-04 15:46:37 -0700 | [diff] [blame] | 764 | ret += sizeof(msg); |
| 765 | buf += sizeof(msg); |
| 766 | count -= sizeof(msg); |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 767 | /* |
| 768 | * Allow to read more than one fault at time but only |
| 769 | * block if waiting for the very first one. |
| 770 | */ |
| 771 | no_wait = O_NONBLOCK; |
| 772 | } |
| 773 | } |
| 774 | |
| 775 | static void __wake_userfault(struct userfaultfd_ctx *ctx, |
| 776 | struct userfaultfd_wake_range *range) |
| 777 | { |
| 778 | unsigned long start, end; |
| 779 | |
| 780 | start = range->start; |
| 781 | end = range->start + range->len; |
| 782 | |
Andrea Arcangeli | 15b726e | 2015-09-04 15:46:44 -0700 | [diff] [blame] | 783 | spin_lock(&ctx->fault_pending_wqh.lock); |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 784 | /* wake all in the range and autoremove */ |
Andrea Arcangeli | 15b726e | 2015-09-04 15:46:44 -0700 | [diff] [blame] | 785 | if (waitqueue_active(&ctx->fault_pending_wqh)) |
Andrea Arcangeli | ac5be6b | 2015-09-22 14:58:49 -0700 | [diff] [blame] | 786 | __wake_up_locked_key(&ctx->fault_pending_wqh, TASK_NORMAL, |
Andrea Arcangeli | 15b726e | 2015-09-04 15:46:44 -0700 | [diff] [blame] | 787 | range); |
| 788 | if (waitqueue_active(&ctx->fault_wqh)) |
Andrea Arcangeli | ac5be6b | 2015-09-22 14:58:49 -0700 | [diff] [blame] | 789 | __wake_up_locked_key(&ctx->fault_wqh, TASK_NORMAL, range); |
Andrea Arcangeli | 15b726e | 2015-09-04 15:46:44 -0700 | [diff] [blame] | 790 | spin_unlock(&ctx->fault_pending_wqh.lock); |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 791 | } |
| 792 | |
| 793 | static __always_inline void wake_userfault(struct userfaultfd_ctx *ctx, |
| 794 | struct userfaultfd_wake_range *range) |
| 795 | { |
Andrea Arcangeli | 2c5b7e1 | 2015-09-04 15:47:23 -0700 | [diff] [blame] | 796 | unsigned seq; |
| 797 | bool need_wakeup; |
| 798 | |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 799 | /* |
| 800 | * To be sure waitqueue_active() is not reordered by the CPU |
| 801 | * before the pagetable update, use an explicit SMP memory |
| 802 | * barrier here. PT lock release or up_read(mmap_sem) still |
| 803 | * have release semantics that can allow the |
| 804 | * waitqueue_active() to be reordered before the pte update. |
| 805 | */ |
| 806 | smp_mb(); |
| 807 | |
| 808 | /* |
| 809 | * Use waitqueue_active because it's very frequent to |
| 810 | * change the address space atomically even if there are no |
| 811 | * userfaults yet. So we take the spinlock only when we're |
| 812 | * sure we've userfaults to wake. |
| 813 | */ |
Andrea Arcangeli | 2c5b7e1 | 2015-09-04 15:47:23 -0700 | [diff] [blame] | 814 | do { |
| 815 | seq = read_seqcount_begin(&ctx->refile_seq); |
| 816 | need_wakeup = waitqueue_active(&ctx->fault_pending_wqh) || |
| 817 | waitqueue_active(&ctx->fault_wqh); |
| 818 | cond_resched(); |
| 819 | } while (read_seqcount_retry(&ctx->refile_seq, seq)); |
| 820 | if (need_wakeup) |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 821 | __wake_userfault(ctx, range); |
| 822 | } |
| 823 | |
| 824 | static __always_inline int validate_range(struct mm_struct *mm, |
| 825 | __u64 start, __u64 len) |
| 826 | { |
| 827 | __u64 task_size = mm->task_size; |
| 828 | |
| 829 | if (start & ~PAGE_MASK) |
| 830 | return -EINVAL; |
| 831 | if (len & ~PAGE_MASK) |
| 832 | return -EINVAL; |
| 833 | if (!len) |
| 834 | return -EINVAL; |
| 835 | if (start < mmap_min_addr) |
| 836 | return -EINVAL; |
| 837 | if (start >= task_size) |
| 838 | return -EINVAL; |
| 839 | if (len > task_size - start) |
| 840 | return -EINVAL; |
| 841 | return 0; |
| 842 | } |
| 843 | |
| 844 | static int userfaultfd_register(struct userfaultfd_ctx *ctx, |
| 845 | unsigned long arg) |
| 846 | { |
| 847 | struct mm_struct *mm = ctx->mm; |
| 848 | struct vm_area_struct *vma, *prev, *cur; |
| 849 | int ret; |
| 850 | struct uffdio_register uffdio_register; |
| 851 | struct uffdio_register __user *user_uffdio_register; |
| 852 | unsigned long vm_flags, new_flags; |
| 853 | bool found; |
| 854 | unsigned long start, end, vma_end; |
| 855 | |
| 856 | user_uffdio_register = (struct uffdio_register __user *) arg; |
| 857 | |
| 858 | ret = -EFAULT; |
| 859 | if (copy_from_user(&uffdio_register, user_uffdio_register, |
| 860 | sizeof(uffdio_register)-sizeof(__u64))) |
| 861 | goto out; |
| 862 | |
| 863 | ret = -EINVAL; |
| 864 | if (!uffdio_register.mode) |
| 865 | goto out; |
| 866 | if (uffdio_register.mode & ~(UFFDIO_REGISTER_MODE_MISSING| |
| 867 | UFFDIO_REGISTER_MODE_WP)) |
| 868 | goto out; |
| 869 | vm_flags = 0; |
| 870 | if (uffdio_register.mode & UFFDIO_REGISTER_MODE_MISSING) |
| 871 | vm_flags |= VM_UFFD_MISSING; |
| 872 | if (uffdio_register.mode & UFFDIO_REGISTER_MODE_WP) { |
| 873 | vm_flags |= VM_UFFD_WP; |
| 874 | /* |
| 875 | * FIXME: remove the below error constraint by |
| 876 | * implementing the wprotect tracking mode. |
| 877 | */ |
| 878 | ret = -EINVAL; |
| 879 | goto out; |
| 880 | } |
| 881 | |
| 882 | ret = validate_range(mm, uffdio_register.range.start, |
| 883 | uffdio_register.range.len); |
| 884 | if (ret) |
| 885 | goto out; |
| 886 | |
| 887 | start = uffdio_register.range.start; |
| 888 | end = start + uffdio_register.range.len; |
| 889 | |
Oleg Nesterov | d2005e3 | 2016-05-20 16:58:36 -0700 | [diff] [blame] | 890 | ret = -ENOMEM; |
| 891 | if (!mmget_not_zero(mm)) |
| 892 | goto out; |
| 893 | |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 894 | down_write(&mm->mmap_sem); |
| 895 | vma = find_vma_prev(mm, start, &prev); |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 896 | if (!vma) |
| 897 | goto out_unlock; |
| 898 | |
| 899 | /* check that there's at least one vma in the range */ |
| 900 | ret = -EINVAL; |
| 901 | if (vma->vm_start >= end) |
| 902 | goto out_unlock; |
| 903 | |
| 904 | /* |
| 905 | * Search for not compatible vmas. |
| 906 | * |
| 907 | * FIXME: this shall be relaxed later so that it doesn't fail |
| 908 | * on tmpfs backed vmas (in addition to the current allowance |
| 909 | * on anonymous vmas). |
| 910 | */ |
| 911 | found = false; |
| 912 | for (cur = vma; cur && cur->vm_start < end; cur = cur->vm_next) { |
| 913 | cond_resched(); |
| 914 | |
| 915 | BUG_ON(!!cur->vm_userfaultfd_ctx.ctx ^ |
| 916 | !!(cur->vm_flags & (VM_UFFD_MISSING | VM_UFFD_WP))); |
| 917 | |
| 918 | /* check not compatible vmas */ |
| 919 | ret = -EINVAL; |
Andrea Arcangeli | a94720bf | 2017-02-22 15:42:15 -0800 | [diff] [blame] | 920 | if (!vma_is_anonymous(cur)) |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 921 | goto out_unlock; |
| 922 | |
| 923 | /* |
| 924 | * Check that this vma isn't already owned by a |
| 925 | * different userfaultfd. We can't allow more than one |
| 926 | * userfaultfd to own a single vma simultaneously or we |
| 927 | * wouldn't know which one to deliver the userfaults to. |
| 928 | */ |
| 929 | ret = -EBUSY; |
| 930 | if (cur->vm_userfaultfd_ctx.ctx && |
| 931 | cur->vm_userfaultfd_ctx.ctx != ctx) |
| 932 | goto out_unlock; |
| 933 | |
| 934 | found = true; |
| 935 | } |
| 936 | BUG_ON(!found); |
| 937 | |
| 938 | if (vma->vm_start < start) |
| 939 | prev = vma; |
| 940 | |
| 941 | ret = 0; |
| 942 | do { |
| 943 | cond_resched(); |
| 944 | |
Andrea Arcangeli | a94720bf | 2017-02-22 15:42:15 -0800 | [diff] [blame] | 945 | BUG_ON(!vma_is_anonymous(vma)); |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 946 | BUG_ON(vma->vm_userfaultfd_ctx.ctx && |
| 947 | vma->vm_userfaultfd_ctx.ctx != ctx); |
| 948 | |
| 949 | /* |
| 950 | * Nothing to do: this vma is already registered into this |
| 951 | * userfaultfd and with the right tracking mode too. |
| 952 | */ |
| 953 | if (vma->vm_userfaultfd_ctx.ctx == ctx && |
| 954 | (vma->vm_flags & vm_flags) == vm_flags) |
| 955 | goto skip; |
| 956 | |
| 957 | if (vma->vm_start > start) |
| 958 | start = vma->vm_start; |
| 959 | vma_end = min(end, vma->vm_end); |
| 960 | |
| 961 | new_flags = (vma->vm_flags & ~vm_flags) | vm_flags; |
| 962 | prev = vma_merge(mm, prev, start, vma_end, new_flags, |
| 963 | vma->anon_vma, vma->vm_file, vma->vm_pgoff, |
| 964 | vma_policy(vma), |
| 965 | ((struct vm_userfaultfd_ctx){ ctx })); |
| 966 | if (prev) { |
| 967 | vma = prev; |
| 968 | goto next; |
| 969 | } |
| 970 | if (vma->vm_start < start) { |
| 971 | ret = split_vma(mm, vma, start, 1); |
| 972 | if (ret) |
| 973 | break; |
| 974 | } |
| 975 | if (vma->vm_end > end) { |
| 976 | ret = split_vma(mm, vma, end, 0); |
| 977 | if (ret) |
| 978 | break; |
| 979 | } |
| 980 | next: |
| 981 | /* |
| 982 | * In the vma_merge() successful mprotect-like case 8: |
| 983 | * the next vma was merged into the current one and |
| 984 | * the current one has not been updated yet. |
| 985 | */ |
| 986 | vma->vm_flags = new_flags; |
| 987 | vma->vm_userfaultfd_ctx.ctx = ctx; |
| 988 | |
| 989 | skip: |
| 990 | prev = vma; |
| 991 | start = vma->vm_end; |
| 992 | vma = vma->vm_next; |
| 993 | } while (vma && vma->vm_start < end); |
| 994 | out_unlock: |
| 995 | up_write(&mm->mmap_sem); |
Oleg Nesterov | d2005e3 | 2016-05-20 16:58:36 -0700 | [diff] [blame] | 996 | mmput(mm); |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 997 | if (!ret) { |
| 998 | /* |
| 999 | * Now that we scanned all vmas we can already tell |
| 1000 | * userland which ioctls methods are guaranteed to |
| 1001 | * succeed on this range. |
| 1002 | */ |
| 1003 | if (put_user(UFFD_API_RANGE_IOCTLS, |
| 1004 | &user_uffdio_register->ioctls)) |
| 1005 | ret = -EFAULT; |
| 1006 | } |
| 1007 | out: |
| 1008 | return ret; |
| 1009 | } |
| 1010 | |
| 1011 | static int userfaultfd_unregister(struct userfaultfd_ctx *ctx, |
| 1012 | unsigned long arg) |
| 1013 | { |
| 1014 | struct mm_struct *mm = ctx->mm; |
| 1015 | struct vm_area_struct *vma, *prev, *cur; |
| 1016 | int ret; |
| 1017 | struct uffdio_range uffdio_unregister; |
| 1018 | unsigned long new_flags; |
| 1019 | bool found; |
| 1020 | unsigned long start, end, vma_end; |
| 1021 | const void __user *buf = (void __user *)arg; |
| 1022 | |
| 1023 | ret = -EFAULT; |
| 1024 | if (copy_from_user(&uffdio_unregister, buf, sizeof(uffdio_unregister))) |
| 1025 | goto out; |
| 1026 | |
| 1027 | ret = validate_range(mm, uffdio_unregister.start, |
| 1028 | uffdio_unregister.len); |
| 1029 | if (ret) |
| 1030 | goto out; |
| 1031 | |
| 1032 | start = uffdio_unregister.start; |
| 1033 | end = start + uffdio_unregister.len; |
| 1034 | |
Oleg Nesterov | d2005e3 | 2016-05-20 16:58:36 -0700 | [diff] [blame] | 1035 | ret = -ENOMEM; |
| 1036 | if (!mmget_not_zero(mm)) |
| 1037 | goto out; |
| 1038 | |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 1039 | down_write(&mm->mmap_sem); |
| 1040 | vma = find_vma_prev(mm, start, &prev); |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 1041 | if (!vma) |
| 1042 | goto out_unlock; |
| 1043 | |
| 1044 | /* check that there's at least one vma in the range */ |
| 1045 | ret = -EINVAL; |
| 1046 | if (vma->vm_start >= end) |
| 1047 | goto out_unlock; |
| 1048 | |
| 1049 | /* |
| 1050 | * Search for not compatible vmas. |
| 1051 | * |
| 1052 | * FIXME: this shall be relaxed later so that it doesn't fail |
| 1053 | * on tmpfs backed vmas (in addition to the current allowance |
| 1054 | * on anonymous vmas). |
| 1055 | */ |
| 1056 | found = false; |
| 1057 | ret = -EINVAL; |
| 1058 | for (cur = vma; cur && cur->vm_start < end; cur = cur->vm_next) { |
| 1059 | cond_resched(); |
| 1060 | |
| 1061 | BUG_ON(!!cur->vm_userfaultfd_ctx.ctx ^ |
| 1062 | !!(cur->vm_flags & (VM_UFFD_MISSING | VM_UFFD_WP))); |
| 1063 | |
| 1064 | /* |
| 1065 | * Check not compatible vmas, not strictly required |
| 1066 | * here as not compatible vmas cannot have an |
| 1067 | * userfaultfd_ctx registered on them, but this |
| 1068 | * provides for more strict behavior to notice |
| 1069 | * unregistration errors. |
| 1070 | */ |
Andrea Arcangeli | a94720bf | 2017-02-22 15:42:15 -0800 | [diff] [blame] | 1071 | if (!vma_is_anonymous(cur)) |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 1072 | goto out_unlock; |
| 1073 | |
| 1074 | found = true; |
| 1075 | } |
| 1076 | BUG_ON(!found); |
| 1077 | |
| 1078 | if (vma->vm_start < start) |
| 1079 | prev = vma; |
| 1080 | |
| 1081 | ret = 0; |
| 1082 | do { |
| 1083 | cond_resched(); |
| 1084 | |
Andrea Arcangeli | a94720bf | 2017-02-22 15:42:15 -0800 | [diff] [blame] | 1085 | BUG_ON(!vma_is_anonymous(vma)); |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 1086 | |
| 1087 | /* |
| 1088 | * Nothing to do: this vma is already registered into this |
| 1089 | * userfaultfd and with the right tracking mode too. |
| 1090 | */ |
| 1091 | if (!vma->vm_userfaultfd_ctx.ctx) |
| 1092 | goto skip; |
| 1093 | |
| 1094 | if (vma->vm_start > start) |
| 1095 | start = vma->vm_start; |
| 1096 | vma_end = min(end, vma->vm_end); |
| 1097 | |
| 1098 | new_flags = vma->vm_flags & ~(VM_UFFD_MISSING | VM_UFFD_WP); |
| 1099 | prev = vma_merge(mm, prev, start, vma_end, new_flags, |
| 1100 | vma->anon_vma, vma->vm_file, vma->vm_pgoff, |
| 1101 | vma_policy(vma), |
| 1102 | NULL_VM_UFFD_CTX); |
| 1103 | if (prev) { |
| 1104 | vma = prev; |
| 1105 | goto next; |
| 1106 | } |
| 1107 | if (vma->vm_start < start) { |
| 1108 | ret = split_vma(mm, vma, start, 1); |
| 1109 | if (ret) |
| 1110 | break; |
| 1111 | } |
| 1112 | if (vma->vm_end > end) { |
| 1113 | ret = split_vma(mm, vma, end, 0); |
| 1114 | if (ret) |
| 1115 | break; |
| 1116 | } |
| 1117 | next: |
| 1118 | /* |
| 1119 | * In the vma_merge() successful mprotect-like case 8: |
| 1120 | * the next vma was merged into the current one and |
| 1121 | * the current one has not been updated yet. |
| 1122 | */ |
| 1123 | vma->vm_flags = new_flags; |
| 1124 | vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX; |
| 1125 | |
| 1126 | skip: |
| 1127 | prev = vma; |
| 1128 | start = vma->vm_end; |
| 1129 | vma = vma->vm_next; |
| 1130 | } while (vma && vma->vm_start < end); |
| 1131 | out_unlock: |
| 1132 | up_write(&mm->mmap_sem); |
Oleg Nesterov | d2005e3 | 2016-05-20 16:58:36 -0700 | [diff] [blame] | 1133 | mmput(mm); |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 1134 | out: |
| 1135 | return ret; |
| 1136 | } |
| 1137 | |
| 1138 | /* |
Andrea Arcangeli | ba85c70 | 2015-09-04 15:46:41 -0700 | [diff] [blame] | 1139 | * userfaultfd_wake may be used in combination with the |
| 1140 | * UFFDIO_*_MODE_DONTWAKE to wakeup userfaults in batches. |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 1141 | */ |
| 1142 | static int userfaultfd_wake(struct userfaultfd_ctx *ctx, |
| 1143 | unsigned long arg) |
| 1144 | { |
| 1145 | int ret; |
| 1146 | struct uffdio_range uffdio_wake; |
| 1147 | struct userfaultfd_wake_range range; |
| 1148 | const void __user *buf = (void __user *)arg; |
| 1149 | |
| 1150 | ret = -EFAULT; |
| 1151 | if (copy_from_user(&uffdio_wake, buf, sizeof(uffdio_wake))) |
| 1152 | goto out; |
| 1153 | |
| 1154 | ret = validate_range(ctx->mm, uffdio_wake.start, uffdio_wake.len); |
| 1155 | if (ret) |
| 1156 | goto out; |
| 1157 | |
| 1158 | range.start = uffdio_wake.start; |
| 1159 | range.len = uffdio_wake.len; |
| 1160 | |
| 1161 | /* |
| 1162 | * len == 0 means wake all and we don't want to wake all here, |
| 1163 | * so check it again to be sure. |
| 1164 | */ |
| 1165 | VM_BUG_ON(!range.len); |
| 1166 | |
| 1167 | wake_userfault(ctx, &range); |
| 1168 | ret = 0; |
| 1169 | |
| 1170 | out: |
| 1171 | return ret; |
| 1172 | } |
| 1173 | |
Andrea Arcangeli | ad465cae | 2015-09-04 15:47:11 -0700 | [diff] [blame] | 1174 | static int userfaultfd_copy(struct userfaultfd_ctx *ctx, |
| 1175 | unsigned long arg) |
| 1176 | { |
| 1177 | __s64 ret; |
| 1178 | struct uffdio_copy uffdio_copy; |
| 1179 | struct uffdio_copy __user *user_uffdio_copy; |
| 1180 | struct userfaultfd_wake_range range; |
| 1181 | |
| 1182 | user_uffdio_copy = (struct uffdio_copy __user *) arg; |
| 1183 | |
| 1184 | ret = -EFAULT; |
| 1185 | if (copy_from_user(&uffdio_copy, user_uffdio_copy, |
| 1186 | /* don't copy "copy" last field */ |
| 1187 | sizeof(uffdio_copy)-sizeof(__s64))) |
| 1188 | goto out; |
| 1189 | |
| 1190 | ret = validate_range(ctx->mm, uffdio_copy.dst, uffdio_copy.len); |
| 1191 | if (ret) |
| 1192 | goto out; |
| 1193 | /* |
| 1194 | * double check for wraparound just in case. copy_from_user() |
| 1195 | * will later check uffdio_copy.src + uffdio_copy.len to fit |
| 1196 | * in the userland range. |
| 1197 | */ |
| 1198 | ret = -EINVAL; |
| 1199 | if (uffdio_copy.src + uffdio_copy.len <= uffdio_copy.src) |
| 1200 | goto out; |
| 1201 | if (uffdio_copy.mode & ~UFFDIO_COPY_MODE_DONTWAKE) |
| 1202 | goto out; |
Oleg Nesterov | d2005e3 | 2016-05-20 16:58:36 -0700 | [diff] [blame] | 1203 | if (mmget_not_zero(ctx->mm)) { |
| 1204 | ret = mcopy_atomic(ctx->mm, uffdio_copy.dst, uffdio_copy.src, |
| 1205 | uffdio_copy.len); |
| 1206 | mmput(ctx->mm); |
| 1207 | } |
Andrea Arcangeli | ad465cae | 2015-09-04 15:47:11 -0700 | [diff] [blame] | 1208 | if (unlikely(put_user(ret, &user_uffdio_copy->copy))) |
| 1209 | return -EFAULT; |
| 1210 | if (ret < 0) |
| 1211 | goto out; |
| 1212 | BUG_ON(!ret); |
| 1213 | /* len == 0 would wake all */ |
| 1214 | range.len = ret; |
| 1215 | if (!(uffdio_copy.mode & UFFDIO_COPY_MODE_DONTWAKE)) { |
| 1216 | range.start = uffdio_copy.dst; |
| 1217 | wake_userfault(ctx, &range); |
| 1218 | } |
| 1219 | ret = range.len == uffdio_copy.len ? 0 : -EAGAIN; |
| 1220 | out: |
| 1221 | return ret; |
| 1222 | } |
| 1223 | |
| 1224 | static int userfaultfd_zeropage(struct userfaultfd_ctx *ctx, |
| 1225 | unsigned long arg) |
| 1226 | { |
| 1227 | __s64 ret; |
| 1228 | struct uffdio_zeropage uffdio_zeropage; |
| 1229 | struct uffdio_zeropage __user *user_uffdio_zeropage; |
| 1230 | struct userfaultfd_wake_range range; |
| 1231 | |
| 1232 | user_uffdio_zeropage = (struct uffdio_zeropage __user *) arg; |
| 1233 | |
| 1234 | ret = -EFAULT; |
| 1235 | if (copy_from_user(&uffdio_zeropage, user_uffdio_zeropage, |
| 1236 | /* don't copy "zeropage" last field */ |
| 1237 | sizeof(uffdio_zeropage)-sizeof(__s64))) |
| 1238 | goto out; |
| 1239 | |
| 1240 | ret = validate_range(ctx->mm, uffdio_zeropage.range.start, |
| 1241 | uffdio_zeropage.range.len); |
| 1242 | if (ret) |
| 1243 | goto out; |
| 1244 | ret = -EINVAL; |
| 1245 | if (uffdio_zeropage.mode & ~UFFDIO_ZEROPAGE_MODE_DONTWAKE) |
| 1246 | goto out; |
| 1247 | |
Oleg Nesterov | d2005e3 | 2016-05-20 16:58:36 -0700 | [diff] [blame] | 1248 | if (mmget_not_zero(ctx->mm)) { |
| 1249 | ret = mfill_zeropage(ctx->mm, uffdio_zeropage.range.start, |
| 1250 | uffdio_zeropage.range.len); |
| 1251 | mmput(ctx->mm); |
| 1252 | } |
Andrea Arcangeli | ad465cae | 2015-09-04 15:47:11 -0700 | [diff] [blame] | 1253 | if (unlikely(put_user(ret, &user_uffdio_zeropage->zeropage))) |
| 1254 | return -EFAULT; |
| 1255 | if (ret < 0) |
| 1256 | goto out; |
| 1257 | /* len == 0 would wake all */ |
| 1258 | BUG_ON(!ret); |
| 1259 | range.len = ret; |
| 1260 | if (!(uffdio_zeropage.mode & UFFDIO_ZEROPAGE_MODE_DONTWAKE)) { |
| 1261 | range.start = uffdio_zeropage.range.start; |
| 1262 | wake_userfault(ctx, &range); |
| 1263 | } |
| 1264 | ret = range.len == uffdio_zeropage.range.len ? 0 : -EAGAIN; |
| 1265 | out: |
| 1266 | return ret; |
| 1267 | } |
| 1268 | |
Pavel Emelyanov | 9cd75c3 | 2017-02-22 15:42:21 -0800 | [diff] [blame^] | 1269 | static inline unsigned int uffd_ctx_features(__u64 user_features) |
| 1270 | { |
| 1271 | /* |
| 1272 | * For the current set of features the bits just coincide |
| 1273 | */ |
| 1274 | return (unsigned int)user_features; |
| 1275 | } |
| 1276 | |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 1277 | /* |
| 1278 | * userland asks for a certain API version and we return which bits |
| 1279 | * and ioctl commands are implemented in this kernel for such API |
| 1280 | * version or -EINVAL if unknown. |
| 1281 | */ |
| 1282 | static int userfaultfd_api(struct userfaultfd_ctx *ctx, |
| 1283 | unsigned long arg) |
| 1284 | { |
| 1285 | struct uffdio_api uffdio_api; |
| 1286 | void __user *buf = (void __user *)arg; |
| 1287 | int ret; |
| 1288 | |
| 1289 | ret = -EINVAL; |
| 1290 | if (ctx->state != UFFD_STATE_WAIT_API) |
| 1291 | goto out; |
| 1292 | ret = -EFAULT; |
Andrea Arcangeli | a9b85f9 | 2015-09-04 15:46:37 -0700 | [diff] [blame] | 1293 | if (copy_from_user(&uffdio_api, buf, sizeof(uffdio_api))) |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 1294 | goto out; |
Pavel Emelyanov | 9cd75c3 | 2017-02-22 15:42:21 -0800 | [diff] [blame^] | 1295 | if (uffdio_api.api != UFFD_API || |
| 1296 | (uffdio_api.features & ~UFFD_API_FEATURES)) { |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 1297 | memset(&uffdio_api, 0, sizeof(uffdio_api)); |
| 1298 | if (copy_to_user(buf, &uffdio_api, sizeof(uffdio_api))) |
| 1299 | goto out; |
| 1300 | ret = -EINVAL; |
| 1301 | goto out; |
| 1302 | } |
Pavel Emelyanov | 9cd75c3 | 2017-02-22 15:42:21 -0800 | [diff] [blame^] | 1303 | uffdio_api.features &= UFFD_API_FEATURES; |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 1304 | uffdio_api.ioctls = UFFD_API_IOCTLS; |
| 1305 | ret = -EFAULT; |
| 1306 | if (copy_to_user(buf, &uffdio_api, sizeof(uffdio_api))) |
| 1307 | goto out; |
| 1308 | ctx->state = UFFD_STATE_RUNNING; |
Pavel Emelyanov | 9cd75c3 | 2017-02-22 15:42:21 -0800 | [diff] [blame^] | 1309 | ctx->features = uffd_ctx_features(uffdio_api.features); |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 1310 | ret = 0; |
| 1311 | out: |
| 1312 | return ret; |
| 1313 | } |
| 1314 | |
| 1315 | static long userfaultfd_ioctl(struct file *file, unsigned cmd, |
| 1316 | unsigned long arg) |
| 1317 | { |
| 1318 | int ret = -EINVAL; |
| 1319 | struct userfaultfd_ctx *ctx = file->private_data; |
| 1320 | |
Andrea Arcangeli | e6485a4 | 2015-09-04 15:47:15 -0700 | [diff] [blame] | 1321 | if (cmd != UFFDIO_API && ctx->state == UFFD_STATE_WAIT_API) |
| 1322 | return -EINVAL; |
| 1323 | |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 1324 | switch(cmd) { |
| 1325 | case UFFDIO_API: |
| 1326 | ret = userfaultfd_api(ctx, arg); |
| 1327 | break; |
| 1328 | case UFFDIO_REGISTER: |
| 1329 | ret = userfaultfd_register(ctx, arg); |
| 1330 | break; |
| 1331 | case UFFDIO_UNREGISTER: |
| 1332 | ret = userfaultfd_unregister(ctx, arg); |
| 1333 | break; |
| 1334 | case UFFDIO_WAKE: |
| 1335 | ret = userfaultfd_wake(ctx, arg); |
| 1336 | break; |
Andrea Arcangeli | ad465cae | 2015-09-04 15:47:11 -0700 | [diff] [blame] | 1337 | case UFFDIO_COPY: |
| 1338 | ret = userfaultfd_copy(ctx, arg); |
| 1339 | break; |
| 1340 | case UFFDIO_ZEROPAGE: |
| 1341 | ret = userfaultfd_zeropage(ctx, arg); |
| 1342 | break; |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 1343 | } |
| 1344 | return ret; |
| 1345 | } |
| 1346 | |
| 1347 | #ifdef CONFIG_PROC_FS |
| 1348 | static void userfaultfd_show_fdinfo(struct seq_file *m, struct file *f) |
| 1349 | { |
| 1350 | struct userfaultfd_ctx *ctx = f->private_data; |
| 1351 | wait_queue_t *wq; |
| 1352 | struct userfaultfd_wait_queue *uwq; |
| 1353 | unsigned long pending = 0, total = 0; |
| 1354 | |
Andrea Arcangeli | 15b726e | 2015-09-04 15:46:44 -0700 | [diff] [blame] | 1355 | spin_lock(&ctx->fault_pending_wqh.lock); |
| 1356 | list_for_each_entry(wq, &ctx->fault_pending_wqh.task_list, task_list) { |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 1357 | uwq = container_of(wq, struct userfaultfd_wait_queue, wq); |
Andrea Arcangeli | 15b726e | 2015-09-04 15:46:44 -0700 | [diff] [blame] | 1358 | pending++; |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 1359 | total++; |
| 1360 | } |
Andrea Arcangeli | 15b726e | 2015-09-04 15:46:44 -0700 | [diff] [blame] | 1361 | list_for_each_entry(wq, &ctx->fault_wqh.task_list, task_list) { |
| 1362 | uwq = container_of(wq, struct userfaultfd_wait_queue, wq); |
| 1363 | total++; |
| 1364 | } |
| 1365 | spin_unlock(&ctx->fault_pending_wqh.lock); |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 1366 | |
| 1367 | /* |
| 1368 | * If more protocols will be added, there will be all shown |
| 1369 | * separated by a space. Like this: |
| 1370 | * protocols: aa:... bb:... |
| 1371 | */ |
| 1372 | seq_printf(m, "pending:\t%lu\ntotal:\t%lu\nAPI:\t%Lx:%x:%Lx\n", |
Pavel Emelyanov | 3f602d2 | 2015-09-04 15:46:34 -0700 | [diff] [blame] | 1373 | pending, total, UFFD_API, UFFD_API_FEATURES, |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 1374 | UFFD_API_IOCTLS|UFFD_API_RANGE_IOCTLS); |
| 1375 | } |
| 1376 | #endif |
| 1377 | |
| 1378 | static const struct file_operations userfaultfd_fops = { |
| 1379 | #ifdef CONFIG_PROC_FS |
| 1380 | .show_fdinfo = userfaultfd_show_fdinfo, |
| 1381 | #endif |
| 1382 | .release = userfaultfd_release, |
| 1383 | .poll = userfaultfd_poll, |
| 1384 | .read = userfaultfd_read, |
| 1385 | .unlocked_ioctl = userfaultfd_ioctl, |
| 1386 | .compat_ioctl = userfaultfd_ioctl, |
| 1387 | .llseek = noop_llseek, |
| 1388 | }; |
| 1389 | |
Andrea Arcangeli | 3004ec9 | 2015-09-04 15:46:48 -0700 | [diff] [blame] | 1390 | static void init_once_userfaultfd_ctx(void *mem) |
| 1391 | { |
| 1392 | struct userfaultfd_ctx *ctx = (struct userfaultfd_ctx *) mem; |
| 1393 | |
| 1394 | init_waitqueue_head(&ctx->fault_pending_wqh); |
| 1395 | init_waitqueue_head(&ctx->fault_wqh); |
Pavel Emelyanov | 9cd75c3 | 2017-02-22 15:42:21 -0800 | [diff] [blame^] | 1396 | init_waitqueue_head(&ctx->event_wqh); |
Andrea Arcangeli | 3004ec9 | 2015-09-04 15:46:48 -0700 | [diff] [blame] | 1397 | init_waitqueue_head(&ctx->fd_wqh); |
Andrea Arcangeli | 2c5b7e1 | 2015-09-04 15:47:23 -0700 | [diff] [blame] | 1398 | seqcount_init(&ctx->refile_seq); |
Andrea Arcangeli | 3004ec9 | 2015-09-04 15:46:48 -0700 | [diff] [blame] | 1399 | } |
| 1400 | |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 1401 | /** |
| 1402 | * userfaultfd_file_create - Creates an userfaultfd file pointer. |
| 1403 | * @flags: Flags for the userfaultfd file. |
| 1404 | * |
| 1405 | * This function creates an userfaultfd file pointer, w/out installing |
| 1406 | * it into the fd table. This is useful when the userfaultfd file is |
| 1407 | * used during the initialization of data structures that require |
| 1408 | * extra setup after the userfaultfd creation. So the userfaultfd |
| 1409 | * creation is split into the file pointer creation phase, and the |
| 1410 | * file descriptor installation phase. In this way races with |
| 1411 | * userspace closing the newly installed file descriptor can be |
| 1412 | * avoided. Returns an userfaultfd file pointer, or a proper error |
| 1413 | * pointer. |
| 1414 | */ |
| 1415 | static struct file *userfaultfd_file_create(int flags) |
| 1416 | { |
| 1417 | struct file *file; |
| 1418 | struct userfaultfd_ctx *ctx; |
| 1419 | |
| 1420 | BUG_ON(!current->mm); |
| 1421 | |
| 1422 | /* Check the UFFD_* constants for consistency. */ |
| 1423 | BUILD_BUG_ON(UFFD_CLOEXEC != O_CLOEXEC); |
| 1424 | BUILD_BUG_ON(UFFD_NONBLOCK != O_NONBLOCK); |
| 1425 | |
| 1426 | file = ERR_PTR(-EINVAL); |
| 1427 | if (flags & ~UFFD_SHARED_FCNTL_FLAGS) |
| 1428 | goto out; |
| 1429 | |
| 1430 | file = ERR_PTR(-ENOMEM); |
Andrea Arcangeli | 3004ec9 | 2015-09-04 15:46:48 -0700 | [diff] [blame] | 1431 | ctx = kmem_cache_alloc(userfaultfd_ctx_cachep, GFP_KERNEL); |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 1432 | if (!ctx) |
| 1433 | goto out; |
| 1434 | |
| 1435 | atomic_set(&ctx->refcount, 1); |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 1436 | ctx->flags = flags; |
Pavel Emelyanov | 9cd75c3 | 2017-02-22 15:42:21 -0800 | [diff] [blame^] | 1437 | ctx->features = 0; |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 1438 | ctx->state = UFFD_STATE_WAIT_API; |
| 1439 | ctx->released = false; |
| 1440 | ctx->mm = current->mm; |
| 1441 | /* prevent the mm struct to be freed */ |
Oleg Nesterov | d2005e3 | 2016-05-20 16:58:36 -0700 | [diff] [blame] | 1442 | atomic_inc(&ctx->mm->mm_count); |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 1443 | |
| 1444 | file = anon_inode_getfile("[userfaultfd]", &userfaultfd_fops, ctx, |
| 1445 | O_RDWR | (flags & UFFD_SHARED_FCNTL_FLAGS)); |
Eric Biggers | c03e946f | 2015-09-17 16:01:54 -0700 | [diff] [blame] | 1446 | if (IS_ERR(file)) { |
Oleg Nesterov | d2005e3 | 2016-05-20 16:58:36 -0700 | [diff] [blame] | 1447 | mmdrop(ctx->mm); |
Andrea Arcangeli | 3004ec9 | 2015-09-04 15:46:48 -0700 | [diff] [blame] | 1448 | kmem_cache_free(userfaultfd_ctx_cachep, ctx); |
Eric Biggers | c03e946f | 2015-09-17 16:01:54 -0700 | [diff] [blame] | 1449 | } |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 1450 | out: |
| 1451 | return file; |
| 1452 | } |
| 1453 | |
| 1454 | SYSCALL_DEFINE1(userfaultfd, int, flags) |
| 1455 | { |
| 1456 | int fd, error; |
| 1457 | struct file *file; |
| 1458 | |
| 1459 | error = get_unused_fd_flags(flags & UFFD_SHARED_FCNTL_FLAGS); |
| 1460 | if (error < 0) |
| 1461 | return error; |
| 1462 | fd = error; |
| 1463 | |
| 1464 | file = userfaultfd_file_create(flags); |
| 1465 | if (IS_ERR(file)) { |
| 1466 | error = PTR_ERR(file); |
| 1467 | goto err_put_unused_fd; |
| 1468 | } |
| 1469 | fd_install(fd, file); |
| 1470 | |
| 1471 | return fd; |
| 1472 | |
| 1473 | err_put_unused_fd: |
| 1474 | put_unused_fd(fd); |
| 1475 | |
| 1476 | return error; |
| 1477 | } |
Andrea Arcangeli | 3004ec9 | 2015-09-04 15:46:48 -0700 | [diff] [blame] | 1478 | |
| 1479 | static int __init userfaultfd_init(void) |
| 1480 | { |
| 1481 | userfaultfd_ctx_cachep = kmem_cache_create("userfaultfd_ctx_cache", |
| 1482 | sizeof(struct userfaultfd_ctx), |
| 1483 | 0, |
| 1484 | SLAB_HWCACHE_ALIGN|SLAB_PANIC, |
| 1485 | init_once_userfaultfd_ctx); |
| 1486 | return 0; |
| 1487 | } |
| 1488 | __initcall(userfaultfd_init); |