| 1 | // SPDX-License-Identifier: GPL-2.0 |
| 2 | /* |
| 3 | * linux/fs/file.c |
| 4 | * |
| 5 | * Copyright (C) 1998-1999, Stephen Tweedie and Bill Hawes |
| 6 | * |
| 7 | * Manage the dynamic fd arrays in the process files_struct. |
| 8 | */ |
| 9 | |
| 10 | #include <linux/syscalls.h> |
| 11 | #include <linux/export.h> |
| 12 | #include <linux/fs.h> |
| 13 | #include <linux/kernel.h> |
| 14 | #include <linux/mm.h> |
| 15 | #include <linux/sched/signal.h> |
| 16 | #include <linux/slab.h> |
| 17 | #include <linux/file.h> |
| 18 | #include <linux/fdtable.h> |
| 19 | #include <linux/bitops.h> |
| 20 | #include <linux/spinlock.h> |
| 21 | #include <linux/rcupdate.h> |
| 22 | #include <linux/close_range.h> |
| 23 | #include <net/sock.h> |
| 24 | |
| 25 | #include "internal.h" |
| 26 | |
| 27 | unsigned int sysctl_nr_open __read_mostly = 1024*1024; |
| 28 | unsigned int sysctl_nr_open_min = BITS_PER_LONG; |
| 29 | /* our min() is unusable in constant expressions ;-/ */ |
| 30 | #define __const_min(x, y) ((x) < (y) ? (x) : (y)) |
| 31 | unsigned int sysctl_nr_open_max = |
| 32 | __const_min(INT_MAX, ~(size_t)0/sizeof(void *)) & -BITS_PER_LONG; |
| 33 | |
| 34 | static void __free_fdtable(struct fdtable *fdt) |
| 35 | { |
| 36 | kvfree(fdt->fd); |
| 37 | kvfree(fdt->open_fds); |
| 38 | kfree(fdt); |
| 39 | } |
| 40 | |
| 41 | static void free_fdtable_rcu(struct rcu_head *rcu) |
| 42 | { |
| 43 | __free_fdtable(container_of(rcu, struct fdtable, rcu)); |
| 44 | } |
| 45 | |
| 46 | #define BITBIT_NR(nr) BITS_TO_LONGS(BITS_TO_LONGS(nr)) |
| 47 | #define BITBIT_SIZE(nr) (BITBIT_NR(nr) * sizeof(long)) |
| 48 | |
| 49 | #define fdt_words(fdt) ((fdt)->max_fds / BITS_PER_LONG) // words in ->open_fds |
| 50 | /* |
| 51 | * Copy 'count' fd bits from the old table to the new table and clear the extra |
| 52 | * space if any. This does not copy the file pointers. Called with the files |
| 53 | * spinlock held for write. |
| 54 | */ |
| 55 | static inline void copy_fd_bitmaps(struct fdtable *nfdt, struct fdtable *ofdt, |
| 56 | unsigned int copy_words) |
| 57 | { |
| 58 | unsigned int nwords = fdt_words(nfdt); |
| 59 | |
| 60 | bitmap_copy_and_extend(nfdt->open_fds, ofdt->open_fds, |
| 61 | copy_words * BITS_PER_LONG, nwords * BITS_PER_LONG); |
| 62 | bitmap_copy_and_extend(nfdt->close_on_exec, ofdt->close_on_exec, |
| 63 | copy_words * BITS_PER_LONG, nwords * BITS_PER_LONG); |
| 64 | bitmap_copy_and_extend(nfdt->full_fds_bits, ofdt->full_fds_bits, |
| 65 | copy_words, nwords); |
| 66 | } |
| 67 | |
| 68 | /* |
| 69 | * Copy all file descriptors from the old table to the new, expanded table and |
| 70 | * clear the extra space. Called with the files spinlock held for write. |
| 71 | */ |
| 72 | static void copy_fdtable(struct fdtable *nfdt, struct fdtable *ofdt) |
| 73 | { |
| 74 | size_t cpy, set; |
| 75 | |
| 76 | BUG_ON(nfdt->max_fds < ofdt->max_fds); |
| 77 | |
| 78 | cpy = ofdt->max_fds * sizeof(struct file *); |
| 79 | set = (nfdt->max_fds - ofdt->max_fds) * sizeof(struct file *); |
| 80 | memcpy(nfdt->fd, ofdt->fd, cpy); |
| 81 | memset((char *)nfdt->fd + cpy, 0, set); |
| 82 | |
| 83 | copy_fd_bitmaps(nfdt, ofdt, fdt_words(ofdt)); |
| 84 | } |
| 85 | |
| 86 | /* |
| 87 | * Note how the fdtable bitmap allocations very much have to be a multiple of |
| 88 | * BITS_PER_LONG. This is not only because we walk those things in chunks of |
| 89 | * 'unsigned long' in some places, but simply because that is how the Linux |
| 90 | * kernel bitmaps are defined to work: they are not "bits in an array of bytes", |
| 91 | * they are very much "bits in an array of unsigned long". |
| 92 | * |
| 93 | * The ALIGN(nr, BITS_PER_LONG) here is for clarity: since we just multiplied |
| 94 | * by that "1024/sizeof(ptr)" before, we already know there are sufficient |
| 95 | * clear low bits. Clang seems to realize that, gcc ends up being confused. |
| 96 | * |
| 97 | * On a 128-bit machine, the ALIGN() would actually matter. In the meantime, |
| 98 | * let's consider it documentation (and maybe a test-case for gcc to improve |
| 99 | * its code generation ;) |
| 100 | */ |
| 101 | static struct fdtable * alloc_fdtable(unsigned int nr) |
| 102 | { |
| 103 | struct fdtable *fdt; |
| 104 | void *data; |
| 105 | |
| 106 | /* |
| 107 | * Figure out how many fds we actually want to support in this fdtable. |
| 108 | * Allocation steps are keyed to the size of the fdarray, since it |
| 109 | * grows far faster than any of the other dynamic data. We try to fit |
| 110 | * the fdarray into comfortable page-tuned chunks: starting at 1024B |
| 111 | * and growing in powers of two from there on. |
| 112 | */ |
| 113 | nr /= (1024 / sizeof(struct file *)); |
| 114 | nr = roundup_pow_of_two(nr + 1); |
| 115 | nr *= (1024 / sizeof(struct file *)); |
| 116 | nr = ALIGN(nr, BITS_PER_LONG); |
| 117 | /* |
| 118 | * Note that this can drive nr *below* what we had passed if sysctl_nr_open |
| 119 | * had been set lower between the check in expand_files() and here. Deal |
| 120 | * with that in caller, it's cheaper that way. |
| 121 | * |
| 122 | * We make sure that nr remains a multiple of BITS_PER_LONG - otherwise |
| 123 | * bitmaps handling below becomes unpleasant, to put it mildly... |
| 124 | */ |
| 125 | if (unlikely(nr > sysctl_nr_open)) |
| 126 | nr = ((sysctl_nr_open - 1) | (BITS_PER_LONG - 1)) + 1; |
| 127 | |
| 128 | fdt = kmalloc(sizeof(struct fdtable), GFP_KERNEL_ACCOUNT); |
| 129 | if (!fdt) |
| 130 | goto out; |
| 131 | fdt->max_fds = nr; |
| 132 | data = kvmalloc_array(nr, sizeof(struct file *), GFP_KERNEL_ACCOUNT); |
| 133 | if (!data) |
| 134 | goto out_fdt; |
| 135 | fdt->fd = data; |
| 136 | |
| 137 | data = kvmalloc(max_t(size_t, |
| 138 | 2 * nr / BITS_PER_BYTE + BITBIT_SIZE(nr), L1_CACHE_BYTES), |
| 139 | GFP_KERNEL_ACCOUNT); |
| 140 | if (!data) |
| 141 | goto out_arr; |
| 142 | fdt->open_fds = data; |
| 143 | data += nr / BITS_PER_BYTE; |
| 144 | fdt->close_on_exec = data; |
| 145 | data += nr / BITS_PER_BYTE; |
| 146 | fdt->full_fds_bits = data; |
| 147 | |
| 148 | return fdt; |
| 149 | |
| 150 | out_arr: |
| 151 | kvfree(fdt->fd); |
| 152 | out_fdt: |
| 153 | kfree(fdt); |
| 154 | out: |
| 155 | return NULL; |
| 156 | } |
| 157 | |
| 158 | /* |
| 159 | * Expand the file descriptor table. |
| 160 | * This function will allocate a new fdtable and both fd array and fdset, of |
| 161 | * the given size. |
| 162 | * Return <0 error code on error; 1 on successful completion. |
| 163 | * The files->file_lock should be held on entry, and will be held on exit. |
| 164 | */ |
| 165 | static int expand_fdtable(struct files_struct *files, unsigned int nr) |
| 166 | __releases(files->file_lock) |
| 167 | __acquires(files->file_lock) |
| 168 | { |
| 169 | struct fdtable *new_fdt, *cur_fdt; |
| 170 | |
| 171 | spin_unlock(&files->file_lock); |
| 172 | new_fdt = alloc_fdtable(nr); |
| 173 | |
| 174 | /* make sure all fd_install() have seen resize_in_progress |
| 175 | * or have finished their rcu_read_lock_sched() section. |
| 176 | */ |
| 177 | if (atomic_read(&files->count) > 1) |
| 178 | synchronize_rcu(); |
| 179 | |
| 180 | spin_lock(&files->file_lock); |
| 181 | if (!new_fdt) |
| 182 | return -ENOMEM; |
| 183 | /* |
| 184 | * extremely unlikely race - sysctl_nr_open decreased between the check in |
| 185 | * caller and alloc_fdtable(). Cheaper to catch it here... |
| 186 | */ |
| 187 | if (unlikely(new_fdt->max_fds <= nr)) { |
| 188 | __free_fdtable(new_fdt); |
| 189 | return -EMFILE; |
| 190 | } |
| 191 | cur_fdt = files_fdtable(files); |
| 192 | BUG_ON(nr < cur_fdt->max_fds); |
| 193 | copy_fdtable(new_fdt, cur_fdt); |
| 194 | rcu_assign_pointer(files->fdt, new_fdt); |
| 195 | if (cur_fdt != &files->fdtab) |
| 196 | call_rcu(&cur_fdt->rcu, free_fdtable_rcu); |
| 197 | /* coupled with smp_rmb() in fd_install() */ |
| 198 | smp_wmb(); |
| 199 | return 1; |
| 200 | } |
| 201 | |
| 202 | /* |
| 203 | * Expand files. |
| 204 | * This function will expand the file structures, if the requested size exceeds |
| 205 | * the current capacity and there is room for expansion. |
| 206 | * Return <0 error code on error; 0 when nothing done; 1 when files were |
| 207 | * expanded and execution may have blocked. |
| 208 | * The files->file_lock should be held on entry, and will be held on exit. |
| 209 | */ |
| 210 | static int expand_files(struct files_struct *files, unsigned int nr) |
| 211 | __releases(files->file_lock) |
| 212 | __acquires(files->file_lock) |
| 213 | { |
| 214 | struct fdtable *fdt; |
| 215 | int expanded = 0; |
| 216 | |
| 217 | repeat: |
| 218 | fdt = files_fdtable(files); |
| 219 | |
| 220 | /* Do we need to expand? */ |
| 221 | if (nr < fdt->max_fds) |
| 222 | return expanded; |
| 223 | |
| 224 | /* Can we expand? */ |
| 225 | if (nr >= sysctl_nr_open) |
| 226 | return -EMFILE; |
| 227 | |
| 228 | if (unlikely(files->resize_in_progress)) { |
| 229 | spin_unlock(&files->file_lock); |
| 230 | expanded = 1; |
| 231 | wait_event(files->resize_wait, !files->resize_in_progress); |
| 232 | spin_lock(&files->file_lock); |
| 233 | goto repeat; |
| 234 | } |
| 235 | |
| 236 | /* All good, so we try */ |
| 237 | files->resize_in_progress = true; |
| 238 | expanded = expand_fdtable(files, nr); |
| 239 | files->resize_in_progress = false; |
| 240 | |
| 241 | wake_up_all(&files->resize_wait); |
| 242 | return expanded; |
| 243 | } |
| 244 | |
| 245 | static inline void __set_close_on_exec(unsigned int fd, struct fdtable *fdt) |
| 246 | { |
| 247 | __set_bit(fd, fdt->close_on_exec); |
| 248 | } |
| 249 | |
| 250 | static inline void __clear_close_on_exec(unsigned int fd, struct fdtable *fdt) |
| 251 | { |
| 252 | if (test_bit(fd, fdt->close_on_exec)) |
| 253 | __clear_bit(fd, fdt->close_on_exec); |
| 254 | } |
| 255 | |
| 256 | static inline void __set_open_fd(unsigned int fd, struct fdtable *fdt) |
| 257 | { |
| 258 | __set_bit(fd, fdt->open_fds); |
| 259 | fd /= BITS_PER_LONG; |
| 260 | if (!~fdt->open_fds[fd]) |
| 261 | __set_bit(fd, fdt->full_fds_bits); |
| 262 | } |
| 263 | |
| 264 | static inline void __clear_open_fd(unsigned int fd, struct fdtable *fdt) |
| 265 | { |
| 266 | __clear_bit(fd, fdt->open_fds); |
| 267 | __clear_bit(fd / BITS_PER_LONG, fdt->full_fds_bits); |
| 268 | } |
| 269 | |
| 270 | static inline bool fd_is_open(unsigned int fd, const struct fdtable *fdt) |
| 271 | { |
| 272 | return test_bit(fd, fdt->open_fds); |
| 273 | } |
| 274 | |
| 275 | static unsigned int count_open_files(struct fdtable *fdt) |
| 276 | { |
| 277 | unsigned int size = fdt->max_fds; |
| 278 | unsigned int i; |
| 279 | |
| 280 | /* Find the last open fd */ |
| 281 | for (i = size / BITS_PER_LONG; i > 0; ) { |
| 282 | if (fdt->open_fds[--i]) |
| 283 | break; |
| 284 | } |
| 285 | i = (i + 1) * BITS_PER_LONG; |
| 286 | return i; |
| 287 | } |
| 288 | |
| 289 | /* |
| 290 | * Note that a sane fdtable size always has to be a multiple of |
| 291 | * BITS_PER_LONG, since we have bitmaps that are sized by this. |
| 292 | * |
| 293 | * 'max_fds' will normally already be properly aligned, but it |
| 294 | * turns out that in the close_range() -> __close_range() -> |
| 295 | * unshare_fd() -> dup_fd() -> sane_fdtable_size() we can end |
| 296 | * up having a 'max_fds' value that isn't already aligned. |
| 297 | * |
| 298 | * Rather than make close_range() have to worry about this, |
| 299 | * just make that BITS_PER_LONG alignment be part of a sane |
| 300 | * fdtable size. Becuase that's really what it is. |
| 301 | */ |
| 302 | static unsigned int sane_fdtable_size(struct fdtable *fdt, unsigned int max_fds) |
| 303 | { |
| 304 | unsigned int count; |
| 305 | |
| 306 | count = count_open_files(fdt); |
| 307 | if (max_fds < NR_OPEN_DEFAULT) |
| 308 | max_fds = NR_OPEN_DEFAULT; |
| 309 | return ALIGN(min(count, max_fds), BITS_PER_LONG); |
| 310 | } |
| 311 | |
| 312 | /* |
| 313 | * Allocate a new files structure and copy contents from the |
| 314 | * passed in files structure. |
| 315 | * errorp will be valid only when the returned files_struct is NULL. |
| 316 | */ |
| 317 | struct files_struct *dup_fd(struct files_struct *oldf, unsigned int max_fds, int *errorp) |
| 318 | { |
| 319 | struct files_struct *newf; |
| 320 | struct file **old_fds, **new_fds; |
| 321 | unsigned int open_files, i; |
| 322 | struct fdtable *old_fdt, *new_fdt; |
| 323 | |
| 324 | *errorp = -ENOMEM; |
| 325 | newf = kmem_cache_alloc(files_cachep, GFP_KERNEL); |
| 326 | if (!newf) |
| 327 | goto out; |
| 328 | |
| 329 | atomic_set(&newf->count, 1); |
| 330 | |
| 331 | spin_lock_init(&newf->file_lock); |
| 332 | newf->resize_in_progress = false; |
| 333 | init_waitqueue_head(&newf->resize_wait); |
| 334 | newf->next_fd = 0; |
| 335 | new_fdt = &newf->fdtab; |
| 336 | new_fdt->max_fds = NR_OPEN_DEFAULT; |
| 337 | new_fdt->close_on_exec = newf->close_on_exec_init; |
| 338 | new_fdt->open_fds = newf->open_fds_init; |
| 339 | new_fdt->full_fds_bits = newf->full_fds_bits_init; |
| 340 | new_fdt->fd = &newf->fd_array[0]; |
| 341 | |
| 342 | spin_lock(&oldf->file_lock); |
| 343 | old_fdt = files_fdtable(oldf); |
| 344 | open_files = sane_fdtable_size(old_fdt, max_fds); |
| 345 | |
| 346 | /* |
| 347 | * Check whether we need to allocate a larger fd array and fd set. |
| 348 | */ |
| 349 | while (unlikely(open_files > new_fdt->max_fds)) { |
| 350 | spin_unlock(&oldf->file_lock); |
| 351 | |
| 352 | if (new_fdt != &newf->fdtab) |
| 353 | __free_fdtable(new_fdt); |
| 354 | |
| 355 | new_fdt = alloc_fdtable(open_files - 1); |
| 356 | if (!new_fdt) { |
| 357 | *errorp = -ENOMEM; |
| 358 | goto out_release; |
| 359 | } |
| 360 | |
| 361 | /* beyond sysctl_nr_open; nothing to do */ |
| 362 | if (unlikely(new_fdt->max_fds < open_files)) { |
| 363 | __free_fdtable(new_fdt); |
| 364 | *errorp = -EMFILE; |
| 365 | goto out_release; |
| 366 | } |
| 367 | |
| 368 | /* |
| 369 | * Reacquire the oldf lock and a pointer to its fd table |
| 370 | * who knows it may have a new bigger fd table. We need |
| 371 | * the latest pointer. |
| 372 | */ |
| 373 | spin_lock(&oldf->file_lock); |
| 374 | old_fdt = files_fdtable(oldf); |
| 375 | open_files = sane_fdtable_size(old_fdt, max_fds); |
| 376 | } |
| 377 | |
| 378 | copy_fd_bitmaps(new_fdt, old_fdt, open_files / BITS_PER_LONG); |
| 379 | |
| 380 | old_fds = old_fdt->fd; |
| 381 | new_fds = new_fdt->fd; |
| 382 | |
| 383 | for (i = open_files; i != 0; i--) { |
| 384 | struct file *f = *old_fds++; |
| 385 | if (f) { |
| 386 | get_file(f); |
| 387 | } else { |
| 388 | /* |
| 389 | * The fd may be claimed in the fd bitmap but not yet |
| 390 | * instantiated in the files array if a sibling thread |
| 391 | * is partway through open(). So make sure that this |
| 392 | * fd is available to the new process. |
| 393 | */ |
| 394 | __clear_open_fd(open_files - i, new_fdt); |
| 395 | } |
| 396 | rcu_assign_pointer(*new_fds++, f); |
| 397 | } |
| 398 | spin_unlock(&oldf->file_lock); |
| 399 | |
| 400 | /* clear the remainder */ |
| 401 | memset(new_fds, 0, (new_fdt->max_fds - open_files) * sizeof(struct file *)); |
| 402 | |
| 403 | rcu_assign_pointer(newf->fdt, new_fdt); |
| 404 | |
| 405 | return newf; |
| 406 | |
| 407 | out_release: |
| 408 | kmem_cache_free(files_cachep, newf); |
| 409 | out: |
| 410 | return NULL; |
| 411 | } |
| 412 | |
| 413 | static struct fdtable *close_files(struct files_struct * files) |
| 414 | { |
| 415 | /* |
| 416 | * It is safe to dereference the fd table without RCU or |
| 417 | * ->file_lock because this is the last reference to the |
| 418 | * files structure. |
| 419 | */ |
| 420 | struct fdtable *fdt = rcu_dereference_raw(files->fdt); |
| 421 | unsigned int i, j = 0; |
| 422 | |
| 423 | for (;;) { |
| 424 | unsigned long set; |
| 425 | i = j * BITS_PER_LONG; |
| 426 | if (i >= fdt->max_fds) |
| 427 | break; |
| 428 | set = fdt->open_fds[j++]; |
| 429 | while (set) { |
| 430 | if (set & 1) { |
| 431 | struct file * file = xchg(&fdt->fd[i], NULL); |
| 432 | if (file) { |
| 433 | filp_close(file, files); |
| 434 | cond_resched(); |
| 435 | } |
| 436 | } |
| 437 | i++; |
| 438 | set >>= 1; |
| 439 | } |
| 440 | } |
| 441 | |
| 442 | return fdt; |
| 443 | } |
| 444 | |
| 445 | void put_files_struct(struct files_struct *files) |
| 446 | { |
| 447 | if (atomic_dec_and_test(&files->count)) { |
| 448 | struct fdtable *fdt = close_files(files); |
| 449 | |
| 450 | /* free the arrays if they are not embedded */ |
| 451 | if (fdt != &files->fdtab) |
| 452 | __free_fdtable(fdt); |
| 453 | kmem_cache_free(files_cachep, files); |
| 454 | } |
| 455 | } |
| 456 | |
| 457 | void exit_files(struct task_struct *tsk) |
| 458 | { |
| 459 | struct files_struct * files = tsk->files; |
| 460 | |
| 461 | if (files) { |
| 462 | task_lock(tsk); |
| 463 | tsk->files = NULL; |
| 464 | task_unlock(tsk); |
| 465 | put_files_struct(files); |
| 466 | } |
| 467 | } |
| 468 | |
| 469 | struct files_struct init_files = { |
| 470 | .count = ATOMIC_INIT(1), |
| 471 | .fdt = &init_files.fdtab, |
| 472 | .fdtab = { |
| 473 | .max_fds = NR_OPEN_DEFAULT, |
| 474 | .fd = &init_files.fd_array[0], |
| 475 | .close_on_exec = init_files.close_on_exec_init, |
| 476 | .open_fds = init_files.open_fds_init, |
| 477 | .full_fds_bits = init_files.full_fds_bits_init, |
| 478 | }, |
| 479 | .file_lock = __SPIN_LOCK_UNLOCKED(init_files.file_lock), |
| 480 | .resize_wait = __WAIT_QUEUE_HEAD_INITIALIZER(init_files.resize_wait), |
| 481 | }; |
| 482 | |
| 483 | static unsigned int find_next_fd(struct fdtable *fdt, unsigned int start) |
| 484 | { |
| 485 | unsigned int maxfd = fdt->max_fds; /* always multiple of BITS_PER_LONG */ |
| 486 | unsigned int maxbit = maxfd / BITS_PER_LONG; |
| 487 | unsigned int bitbit = start / BITS_PER_LONG; |
| 488 | |
| 489 | bitbit = find_next_zero_bit(fdt->full_fds_bits, maxbit, bitbit) * BITS_PER_LONG; |
| 490 | if (bitbit >= maxfd) |
| 491 | return maxfd; |
| 492 | if (bitbit > start) |
| 493 | start = bitbit; |
| 494 | return find_next_zero_bit(fdt->open_fds, maxfd, start); |
| 495 | } |
| 496 | |
| 497 | /* |
| 498 | * allocate a file descriptor, mark it busy. |
| 499 | */ |
| 500 | static int alloc_fd(unsigned start, unsigned end, unsigned flags) |
| 501 | { |
| 502 | struct files_struct *files = current->files; |
| 503 | unsigned int fd; |
| 504 | int error; |
| 505 | struct fdtable *fdt; |
| 506 | |
| 507 | spin_lock(&files->file_lock); |
| 508 | repeat: |
| 509 | fdt = files_fdtable(files); |
| 510 | fd = start; |
| 511 | if (fd < files->next_fd) |
| 512 | fd = files->next_fd; |
| 513 | |
| 514 | if (fd < fdt->max_fds) |
| 515 | fd = find_next_fd(fdt, fd); |
| 516 | |
| 517 | /* |
| 518 | * N.B. For clone tasks sharing a files structure, this test |
| 519 | * will limit the total number of files that can be opened. |
| 520 | */ |
| 521 | error = -EMFILE; |
| 522 | if (fd >= end) |
| 523 | goto out; |
| 524 | |
| 525 | error = expand_files(files, fd); |
| 526 | if (error < 0) |
| 527 | goto out; |
| 528 | |
| 529 | /* |
| 530 | * If we needed to expand the fs array we |
| 531 | * might have blocked - try again. |
| 532 | */ |
| 533 | if (error) |
| 534 | goto repeat; |
| 535 | |
| 536 | if (start <= files->next_fd) |
| 537 | files->next_fd = fd + 1; |
| 538 | |
| 539 | __set_open_fd(fd, fdt); |
| 540 | if (flags & O_CLOEXEC) |
| 541 | __set_close_on_exec(fd, fdt); |
| 542 | else |
| 543 | __clear_close_on_exec(fd, fdt); |
| 544 | error = fd; |
| 545 | #if 1 |
| 546 | /* Sanity check */ |
| 547 | if (rcu_access_pointer(fdt->fd[fd]) != NULL) { |
| 548 | printk(KERN_WARNING "alloc_fd: slot %d not NULL!\n", fd); |
| 549 | rcu_assign_pointer(fdt->fd[fd], NULL); |
| 550 | } |
| 551 | #endif |
| 552 | |
| 553 | out: |
| 554 | spin_unlock(&files->file_lock); |
| 555 | return error; |
| 556 | } |
| 557 | |
| 558 | int __get_unused_fd_flags(unsigned flags, unsigned long nofile) |
| 559 | { |
| 560 | return alloc_fd(0, nofile, flags); |
| 561 | } |
| 562 | |
| 563 | int get_unused_fd_flags(unsigned flags) |
| 564 | { |
| 565 | return __get_unused_fd_flags(flags, rlimit(RLIMIT_NOFILE)); |
| 566 | } |
| 567 | EXPORT_SYMBOL(get_unused_fd_flags); |
| 568 | |
| 569 | static void __put_unused_fd(struct files_struct *files, unsigned int fd) |
| 570 | { |
| 571 | struct fdtable *fdt = files_fdtable(files); |
| 572 | __clear_open_fd(fd, fdt); |
| 573 | if (fd < files->next_fd) |
| 574 | files->next_fd = fd; |
| 575 | } |
| 576 | |
| 577 | void put_unused_fd(unsigned int fd) |
| 578 | { |
| 579 | struct files_struct *files = current->files; |
| 580 | spin_lock(&files->file_lock); |
| 581 | __put_unused_fd(files, fd); |
| 582 | spin_unlock(&files->file_lock); |
| 583 | } |
| 584 | |
| 585 | EXPORT_SYMBOL(put_unused_fd); |
| 586 | |
| 587 | /* |
| 588 | * Install a file pointer in the fd array. |
| 589 | * |
| 590 | * The VFS is full of places where we drop the files lock between |
| 591 | * setting the open_fds bitmap and installing the file in the file |
| 592 | * array. At any such point, we are vulnerable to a dup2() race |
| 593 | * installing a file in the array before us. We need to detect this and |
| 594 | * fput() the struct file we are about to overwrite in this case. |
| 595 | * |
| 596 | * It should never happen - if we allow dup2() do it, _really_ bad things |
| 597 | * will follow. |
| 598 | * |
| 599 | * This consumes the "file" refcount, so callers should treat it |
| 600 | * as if they had called fput(file). |
| 601 | */ |
| 602 | |
| 603 | void fd_install(unsigned int fd, struct file *file) |
| 604 | { |
| 605 | struct files_struct *files = current->files; |
| 606 | struct fdtable *fdt; |
| 607 | |
| 608 | if (WARN_ON_ONCE(unlikely(file->f_mode & FMODE_BACKING))) |
| 609 | return; |
| 610 | |
| 611 | rcu_read_lock_sched(); |
| 612 | |
| 613 | if (unlikely(files->resize_in_progress)) { |
| 614 | rcu_read_unlock_sched(); |
| 615 | spin_lock(&files->file_lock); |
| 616 | fdt = files_fdtable(files); |
| 617 | BUG_ON(fdt->fd[fd] != NULL); |
| 618 | rcu_assign_pointer(fdt->fd[fd], file); |
| 619 | spin_unlock(&files->file_lock); |
| 620 | return; |
| 621 | } |
| 622 | /* coupled with smp_wmb() in expand_fdtable() */ |
| 623 | smp_rmb(); |
| 624 | fdt = rcu_dereference_sched(files->fdt); |
| 625 | BUG_ON(fdt->fd[fd] != NULL); |
| 626 | rcu_assign_pointer(fdt->fd[fd], file); |
| 627 | rcu_read_unlock_sched(); |
| 628 | } |
| 629 | |
| 630 | EXPORT_SYMBOL(fd_install); |
| 631 | |
| 632 | /** |
| 633 | * file_close_fd_locked - return file associated with fd |
| 634 | * @files: file struct to retrieve file from |
| 635 | * @fd: file descriptor to retrieve file for |
| 636 | * |
| 637 | * Doesn't take a separate reference count. |
| 638 | * |
| 639 | * Context: files_lock must be held. |
| 640 | * |
| 641 | * Returns: The file associated with @fd (NULL if @fd is not open) |
| 642 | */ |
| 643 | struct file *file_close_fd_locked(struct files_struct *files, unsigned fd) |
| 644 | { |
| 645 | struct fdtable *fdt = files_fdtable(files); |
| 646 | struct file *file; |
| 647 | |
| 648 | lockdep_assert_held(&files->file_lock); |
| 649 | |
| 650 | if (fd >= fdt->max_fds) |
| 651 | return NULL; |
| 652 | |
| 653 | fd = array_index_nospec(fd, fdt->max_fds); |
| 654 | file = fdt->fd[fd]; |
| 655 | if (file) { |
| 656 | rcu_assign_pointer(fdt->fd[fd], NULL); |
| 657 | __put_unused_fd(files, fd); |
| 658 | } |
| 659 | return file; |
| 660 | } |
| 661 | |
| 662 | int close_fd(unsigned fd) |
| 663 | { |
| 664 | struct files_struct *files = current->files; |
| 665 | struct file *file; |
| 666 | |
| 667 | spin_lock(&files->file_lock); |
| 668 | file = file_close_fd_locked(files, fd); |
| 669 | spin_unlock(&files->file_lock); |
| 670 | if (!file) |
| 671 | return -EBADF; |
| 672 | |
| 673 | return filp_close(file, files); |
| 674 | } |
| 675 | EXPORT_SYMBOL(close_fd); |
| 676 | |
| 677 | /** |
| 678 | * last_fd - return last valid index into fd table |
| 679 | * @fdt: File descriptor table. |
| 680 | * |
| 681 | * Context: Either rcu read lock or files_lock must be held. |
| 682 | * |
| 683 | * Returns: Last valid index into fdtable. |
| 684 | */ |
| 685 | static inline unsigned last_fd(struct fdtable *fdt) |
| 686 | { |
| 687 | return fdt->max_fds - 1; |
| 688 | } |
| 689 | |
| 690 | static inline void __range_cloexec(struct files_struct *cur_fds, |
| 691 | unsigned int fd, unsigned int max_fd) |
| 692 | { |
| 693 | struct fdtable *fdt; |
| 694 | |
| 695 | /* make sure we're using the correct maximum value */ |
| 696 | spin_lock(&cur_fds->file_lock); |
| 697 | fdt = files_fdtable(cur_fds); |
| 698 | max_fd = min(last_fd(fdt), max_fd); |
| 699 | if (fd <= max_fd) |
| 700 | bitmap_set(fdt->close_on_exec, fd, max_fd - fd + 1); |
| 701 | spin_unlock(&cur_fds->file_lock); |
| 702 | } |
| 703 | |
| 704 | static inline void __range_close(struct files_struct *files, unsigned int fd, |
| 705 | unsigned int max_fd) |
| 706 | { |
| 707 | struct file *file; |
| 708 | unsigned n; |
| 709 | |
| 710 | spin_lock(&files->file_lock); |
| 711 | n = last_fd(files_fdtable(files)); |
| 712 | max_fd = min(max_fd, n); |
| 713 | |
| 714 | for (; fd <= max_fd; fd++) { |
| 715 | file = file_close_fd_locked(files, fd); |
| 716 | if (file) { |
| 717 | spin_unlock(&files->file_lock); |
| 718 | filp_close(file, files); |
| 719 | cond_resched(); |
| 720 | spin_lock(&files->file_lock); |
| 721 | } else if (need_resched()) { |
| 722 | spin_unlock(&files->file_lock); |
| 723 | cond_resched(); |
| 724 | spin_lock(&files->file_lock); |
| 725 | } |
| 726 | } |
| 727 | spin_unlock(&files->file_lock); |
| 728 | } |
| 729 | |
| 730 | /** |
| 731 | * __close_range() - Close all file descriptors in a given range. |
| 732 | * |
| 733 | * @fd: starting file descriptor to close |
| 734 | * @max_fd: last file descriptor to close |
| 735 | * @flags: CLOSE_RANGE flags. |
| 736 | * |
| 737 | * This closes a range of file descriptors. All file descriptors |
| 738 | * from @fd up to and including @max_fd are closed. |
| 739 | */ |
| 740 | int __close_range(unsigned fd, unsigned max_fd, unsigned int flags) |
| 741 | { |
| 742 | struct task_struct *me = current; |
| 743 | struct files_struct *cur_fds = me->files, *fds = NULL; |
| 744 | |
| 745 | if (flags & ~(CLOSE_RANGE_UNSHARE | CLOSE_RANGE_CLOEXEC)) |
| 746 | return -EINVAL; |
| 747 | |
| 748 | if (fd > max_fd) |
| 749 | return -EINVAL; |
| 750 | |
| 751 | if (flags & CLOSE_RANGE_UNSHARE) { |
| 752 | int ret; |
| 753 | unsigned int max_unshare_fds = NR_OPEN_MAX; |
| 754 | |
| 755 | /* |
| 756 | * If the caller requested all fds to be made cloexec we always |
| 757 | * copy all of the file descriptors since they still want to |
| 758 | * use them. |
| 759 | */ |
| 760 | if (!(flags & CLOSE_RANGE_CLOEXEC)) { |
| 761 | /* |
| 762 | * If the requested range is greater than the current |
| 763 | * maximum, we're closing everything so only copy all |
| 764 | * file descriptors beneath the lowest file descriptor. |
| 765 | */ |
| 766 | rcu_read_lock(); |
| 767 | if (max_fd >= last_fd(files_fdtable(cur_fds))) |
| 768 | max_unshare_fds = fd; |
| 769 | rcu_read_unlock(); |
| 770 | } |
| 771 | |
| 772 | ret = unshare_fd(CLONE_FILES, max_unshare_fds, &fds); |
| 773 | if (ret) |
| 774 | return ret; |
| 775 | |
| 776 | /* |
| 777 | * We used to share our file descriptor table, and have now |
| 778 | * created a private one, make sure we're using it below. |
| 779 | */ |
| 780 | if (fds) |
| 781 | swap(cur_fds, fds); |
| 782 | } |
| 783 | |
| 784 | if (flags & CLOSE_RANGE_CLOEXEC) |
| 785 | __range_cloexec(cur_fds, fd, max_fd); |
| 786 | else |
| 787 | __range_close(cur_fds, fd, max_fd); |
| 788 | |
| 789 | if (fds) { |
| 790 | /* |
| 791 | * We're done closing the files we were supposed to. Time to install |
| 792 | * the new file descriptor table and drop the old one. |
| 793 | */ |
| 794 | task_lock(me); |
| 795 | me->files = cur_fds; |
| 796 | task_unlock(me); |
| 797 | put_files_struct(fds); |
| 798 | } |
| 799 | |
| 800 | return 0; |
| 801 | } |
| 802 | |
| 803 | /** |
| 804 | * file_close_fd - return file associated with fd |
| 805 | * @fd: file descriptor to retrieve file for |
| 806 | * |
| 807 | * Doesn't take a separate reference count. |
| 808 | * |
| 809 | * Returns: The file associated with @fd (NULL if @fd is not open) |
| 810 | */ |
| 811 | struct file *file_close_fd(unsigned int fd) |
| 812 | { |
| 813 | struct files_struct *files = current->files; |
| 814 | struct file *file; |
| 815 | |
| 816 | spin_lock(&files->file_lock); |
| 817 | file = file_close_fd_locked(files, fd); |
| 818 | spin_unlock(&files->file_lock); |
| 819 | |
| 820 | return file; |
| 821 | } |
| 822 | |
| 823 | void do_close_on_exec(struct files_struct *files) |
| 824 | { |
| 825 | unsigned i; |
| 826 | struct fdtable *fdt; |
| 827 | |
| 828 | /* exec unshares first */ |
| 829 | spin_lock(&files->file_lock); |
| 830 | for (i = 0; ; i++) { |
| 831 | unsigned long set; |
| 832 | unsigned fd = i * BITS_PER_LONG; |
| 833 | fdt = files_fdtable(files); |
| 834 | if (fd >= fdt->max_fds) |
| 835 | break; |
| 836 | set = fdt->close_on_exec[i]; |
| 837 | if (!set) |
| 838 | continue; |
| 839 | fdt->close_on_exec[i] = 0; |
| 840 | for ( ; set ; fd++, set >>= 1) { |
| 841 | struct file *file; |
| 842 | if (!(set & 1)) |
| 843 | continue; |
| 844 | file = fdt->fd[fd]; |
| 845 | if (!file) |
| 846 | continue; |
| 847 | rcu_assign_pointer(fdt->fd[fd], NULL); |
| 848 | __put_unused_fd(files, fd); |
| 849 | spin_unlock(&files->file_lock); |
| 850 | filp_close(file, files); |
| 851 | cond_resched(); |
| 852 | spin_lock(&files->file_lock); |
| 853 | } |
| 854 | |
| 855 | } |
| 856 | spin_unlock(&files->file_lock); |
| 857 | } |
| 858 | |
| 859 | static struct file *__get_file_rcu(struct file __rcu **f) |
| 860 | { |
| 861 | struct file __rcu *file; |
| 862 | struct file __rcu *file_reloaded; |
| 863 | struct file __rcu *file_reloaded_cmp; |
| 864 | |
| 865 | file = rcu_dereference_raw(*f); |
| 866 | if (!file) |
| 867 | return NULL; |
| 868 | |
| 869 | if (unlikely(!atomic_long_inc_not_zero(&file->f_count))) |
| 870 | return ERR_PTR(-EAGAIN); |
| 871 | |
| 872 | file_reloaded = rcu_dereference_raw(*f); |
| 873 | |
| 874 | /* |
| 875 | * Ensure that all accesses have a dependency on the load from |
| 876 | * rcu_dereference_raw() above so we get correct ordering |
| 877 | * between reuse/allocation and the pointer check below. |
| 878 | */ |
| 879 | file_reloaded_cmp = file_reloaded; |
| 880 | OPTIMIZER_HIDE_VAR(file_reloaded_cmp); |
| 881 | |
| 882 | /* |
| 883 | * atomic_long_inc_not_zero() above provided a full memory |
| 884 | * barrier when we acquired a reference. |
| 885 | * |
| 886 | * This is paired with the write barrier from assigning to the |
| 887 | * __rcu protected file pointer so that if that pointer still |
| 888 | * matches the current file, we know we have successfully |
| 889 | * acquired a reference to the right file. |
| 890 | * |
| 891 | * If the pointers don't match the file has been reallocated by |
| 892 | * SLAB_TYPESAFE_BY_RCU. |
| 893 | */ |
| 894 | if (file == file_reloaded_cmp) |
| 895 | return file_reloaded; |
| 896 | |
| 897 | fput(file); |
| 898 | return ERR_PTR(-EAGAIN); |
| 899 | } |
| 900 | |
| 901 | /** |
| 902 | * get_file_rcu - try go get a reference to a file under rcu |
| 903 | * @f: the file to get a reference on |
| 904 | * |
| 905 | * This function tries to get a reference on @f carefully verifying that |
| 906 | * @f hasn't been reused. |
| 907 | * |
| 908 | * This function should rarely have to be used and only by users who |
| 909 | * understand the implications of SLAB_TYPESAFE_BY_RCU. Try to avoid it. |
| 910 | * |
| 911 | * Return: Returns @f with the reference count increased or NULL. |
| 912 | */ |
| 913 | struct file *get_file_rcu(struct file __rcu **f) |
| 914 | { |
| 915 | for (;;) { |
| 916 | struct file __rcu *file; |
| 917 | |
| 918 | file = __get_file_rcu(f); |
| 919 | if (!IS_ERR(file)) |
| 920 | return file; |
| 921 | } |
| 922 | } |
| 923 | EXPORT_SYMBOL_GPL(get_file_rcu); |
| 924 | |
| 925 | /** |
| 926 | * get_file_active - try go get a reference to a file |
| 927 | * @f: the file to get a reference on |
| 928 | * |
| 929 | * In contast to get_file_rcu() the pointer itself isn't part of the |
| 930 | * reference counting. |
| 931 | * |
| 932 | * This function should rarely have to be used and only by users who |
| 933 | * understand the implications of SLAB_TYPESAFE_BY_RCU. Try to avoid it. |
| 934 | * |
| 935 | * Return: Returns @f with the reference count increased or NULL. |
| 936 | */ |
| 937 | struct file *get_file_active(struct file **f) |
| 938 | { |
| 939 | struct file __rcu *file; |
| 940 | |
| 941 | rcu_read_lock(); |
| 942 | file = __get_file_rcu(f); |
| 943 | rcu_read_unlock(); |
| 944 | if (IS_ERR(file)) |
| 945 | file = NULL; |
| 946 | return file; |
| 947 | } |
| 948 | EXPORT_SYMBOL_GPL(get_file_active); |
| 949 | |
| 950 | static inline struct file *__fget_files_rcu(struct files_struct *files, |
| 951 | unsigned int fd, fmode_t mask) |
| 952 | { |
| 953 | for (;;) { |
| 954 | struct file *file; |
| 955 | struct fdtable *fdt = rcu_dereference_raw(files->fdt); |
| 956 | struct file __rcu **fdentry; |
| 957 | unsigned long nospec_mask; |
| 958 | |
| 959 | /* Mask is a 0 for invalid fd's, ~0 for valid ones */ |
| 960 | nospec_mask = array_index_mask_nospec(fd, fdt->max_fds); |
| 961 | |
| 962 | /* |
| 963 | * fdentry points to the 'fd' offset, or fdt->fd[0]. |
| 964 | * Loading from fdt->fd[0] is always safe, because the |
| 965 | * array always exists. |
| 966 | */ |
| 967 | fdentry = fdt->fd + (fd & nospec_mask); |
| 968 | |
| 969 | /* Do the load, then mask any invalid result */ |
| 970 | file = rcu_dereference_raw(*fdentry); |
| 971 | file = (void *)(nospec_mask & (unsigned long)file); |
| 972 | if (unlikely(!file)) |
| 973 | return NULL; |
| 974 | |
| 975 | /* |
| 976 | * Ok, we have a file pointer that was valid at |
| 977 | * some point, but it might have become stale since. |
| 978 | * |
| 979 | * We need to confirm it by incrementing the refcount |
| 980 | * and then check the lookup again. |
| 981 | * |
| 982 | * atomic_long_inc_not_zero() gives us a full memory |
| 983 | * barrier. We only really need an 'acquire' one to |
| 984 | * protect the loads below, but we don't have that. |
| 985 | */ |
| 986 | if (unlikely(!atomic_long_inc_not_zero(&file->f_count))) |
| 987 | continue; |
| 988 | |
| 989 | /* |
| 990 | * Such a race can take two forms: |
| 991 | * |
| 992 | * (a) the file ref already went down to zero and the |
| 993 | * file hasn't been reused yet or the file count |
| 994 | * isn't zero but the file has already been reused. |
| 995 | * |
| 996 | * (b) the file table entry has changed under us. |
| 997 | * Note that we don't need to re-check the 'fdt->fd' |
| 998 | * pointer having changed, because it always goes |
| 999 | * hand-in-hand with 'fdt'. |
| 1000 | * |
| 1001 | * If so, we need to put our ref and try again. |
| 1002 | */ |
| 1003 | if (unlikely(file != rcu_dereference_raw(*fdentry)) || |
| 1004 | unlikely(rcu_dereference_raw(files->fdt) != fdt)) { |
| 1005 | fput(file); |
| 1006 | continue; |
| 1007 | } |
| 1008 | |
| 1009 | /* |
| 1010 | * This isn't the file we're looking for or we're not |
| 1011 | * allowed to get a reference to it. |
| 1012 | */ |
| 1013 | if (unlikely(file->f_mode & mask)) { |
| 1014 | fput(file); |
| 1015 | return NULL; |
| 1016 | } |
| 1017 | |
| 1018 | /* |
| 1019 | * Ok, we have a ref to the file, and checked that it |
| 1020 | * still exists. |
| 1021 | */ |
| 1022 | return file; |
| 1023 | } |
| 1024 | } |
| 1025 | |
| 1026 | static struct file *__fget_files(struct files_struct *files, unsigned int fd, |
| 1027 | fmode_t mask) |
| 1028 | { |
| 1029 | struct file *file; |
| 1030 | |
| 1031 | rcu_read_lock(); |
| 1032 | file = __fget_files_rcu(files, fd, mask); |
| 1033 | rcu_read_unlock(); |
| 1034 | |
| 1035 | return file; |
| 1036 | } |
| 1037 | |
| 1038 | static inline struct file *__fget(unsigned int fd, fmode_t mask) |
| 1039 | { |
| 1040 | return __fget_files(current->files, fd, mask); |
| 1041 | } |
| 1042 | |
| 1043 | struct file *fget(unsigned int fd) |
| 1044 | { |
| 1045 | return __fget(fd, FMODE_PATH); |
| 1046 | } |
| 1047 | EXPORT_SYMBOL(fget); |
| 1048 | |
| 1049 | struct file *fget_raw(unsigned int fd) |
| 1050 | { |
| 1051 | return __fget(fd, 0); |
| 1052 | } |
| 1053 | EXPORT_SYMBOL(fget_raw); |
| 1054 | |
| 1055 | struct file *fget_task(struct task_struct *task, unsigned int fd) |
| 1056 | { |
| 1057 | struct file *file = NULL; |
| 1058 | |
| 1059 | task_lock(task); |
| 1060 | if (task->files) |
| 1061 | file = __fget_files(task->files, fd, 0); |
| 1062 | task_unlock(task); |
| 1063 | |
| 1064 | return file; |
| 1065 | } |
| 1066 | |
| 1067 | struct file *lookup_fdget_rcu(unsigned int fd) |
| 1068 | { |
| 1069 | return __fget_files_rcu(current->files, fd, 0); |
| 1070 | |
| 1071 | } |
| 1072 | EXPORT_SYMBOL_GPL(lookup_fdget_rcu); |
| 1073 | |
| 1074 | struct file *task_lookup_fdget_rcu(struct task_struct *task, unsigned int fd) |
| 1075 | { |
| 1076 | /* Must be called with rcu_read_lock held */ |
| 1077 | struct files_struct *files; |
| 1078 | struct file *file = NULL; |
| 1079 | |
| 1080 | task_lock(task); |
| 1081 | files = task->files; |
| 1082 | if (files) |
| 1083 | file = __fget_files_rcu(files, fd, 0); |
| 1084 | task_unlock(task); |
| 1085 | |
| 1086 | return file; |
| 1087 | } |
| 1088 | |
| 1089 | struct file *task_lookup_next_fdget_rcu(struct task_struct *task, unsigned int *ret_fd) |
| 1090 | { |
| 1091 | /* Must be called with rcu_read_lock held */ |
| 1092 | struct files_struct *files; |
| 1093 | unsigned int fd = *ret_fd; |
| 1094 | struct file *file = NULL; |
| 1095 | |
| 1096 | task_lock(task); |
| 1097 | files = task->files; |
| 1098 | if (files) { |
| 1099 | for (; fd < files_fdtable(files)->max_fds; fd++) { |
| 1100 | file = __fget_files_rcu(files, fd, 0); |
| 1101 | if (file) |
| 1102 | break; |
| 1103 | } |
| 1104 | } |
| 1105 | task_unlock(task); |
| 1106 | *ret_fd = fd; |
| 1107 | return file; |
| 1108 | } |
| 1109 | EXPORT_SYMBOL(task_lookup_next_fdget_rcu); |
| 1110 | |
| 1111 | /* |
| 1112 | * Lightweight file lookup - no refcnt increment if fd table isn't shared. |
| 1113 | * |
| 1114 | * You can use this instead of fget if you satisfy all of the following |
| 1115 | * conditions: |
| 1116 | * 1) You must call fput_light before exiting the syscall and returning control |
| 1117 | * to userspace (i.e. you cannot remember the returned struct file * after |
| 1118 | * returning to userspace). |
| 1119 | * 2) You must not call filp_close on the returned struct file * in between |
| 1120 | * calls to fget_light and fput_light. |
| 1121 | * 3) You must not clone the current task in between the calls to fget_light |
| 1122 | * and fput_light. |
| 1123 | * |
| 1124 | * The fput_needed flag returned by fget_light should be passed to the |
| 1125 | * corresponding fput_light. |
| 1126 | */ |
| 1127 | static inline struct fd __fget_light(unsigned int fd, fmode_t mask) |
| 1128 | { |
| 1129 | struct files_struct *files = current->files; |
| 1130 | struct file *file; |
| 1131 | |
| 1132 | /* |
| 1133 | * If another thread is concurrently calling close_fd() followed |
| 1134 | * by put_files_struct(), we must not observe the old table |
| 1135 | * entry combined with the new refcount - otherwise we could |
| 1136 | * return a file that is concurrently being freed. |
| 1137 | * |
| 1138 | * atomic_read_acquire() pairs with atomic_dec_and_test() in |
| 1139 | * put_files_struct(). |
| 1140 | */ |
| 1141 | if (likely(atomic_read_acquire(&files->count) == 1)) { |
| 1142 | file = files_lookup_fd_raw(files, fd); |
| 1143 | if (!file || unlikely(file->f_mode & mask)) |
| 1144 | return EMPTY_FD; |
| 1145 | return BORROWED_FD(file); |
| 1146 | } else { |
| 1147 | file = __fget_files(files, fd, mask); |
| 1148 | if (!file) |
| 1149 | return EMPTY_FD; |
| 1150 | return CLONED_FD(file); |
| 1151 | } |
| 1152 | } |
| 1153 | struct fd fdget(unsigned int fd) |
| 1154 | { |
| 1155 | return __fget_light(fd, FMODE_PATH); |
| 1156 | } |
| 1157 | EXPORT_SYMBOL(fdget); |
| 1158 | |
| 1159 | struct fd fdget_raw(unsigned int fd) |
| 1160 | { |
| 1161 | return __fget_light(fd, 0); |
| 1162 | } |
| 1163 | |
| 1164 | /* |
| 1165 | * Try to avoid f_pos locking. We only need it if the |
| 1166 | * file is marked for FMODE_ATOMIC_POS, and it can be |
| 1167 | * accessed multiple ways. |
| 1168 | * |
| 1169 | * Always do it for directories, because pidfd_getfd() |
| 1170 | * can make a file accessible even if it otherwise would |
| 1171 | * not be, and for directories this is a correctness |
| 1172 | * issue, not a "POSIX requirement". |
| 1173 | */ |
| 1174 | static inline bool file_needs_f_pos_lock(struct file *file) |
| 1175 | { |
| 1176 | return (file->f_mode & FMODE_ATOMIC_POS) && |
| 1177 | (file_count(file) > 1 || file->f_op->iterate_shared); |
| 1178 | } |
| 1179 | |
| 1180 | struct fd fdget_pos(unsigned int fd) |
| 1181 | { |
| 1182 | struct fd f = fdget(fd); |
| 1183 | struct file *file = fd_file(f); |
| 1184 | |
| 1185 | if (file && file_needs_f_pos_lock(file)) { |
| 1186 | f.word |= FDPUT_POS_UNLOCK; |
| 1187 | mutex_lock(&file->f_pos_lock); |
| 1188 | } |
| 1189 | return f; |
| 1190 | } |
| 1191 | |
| 1192 | void __f_unlock_pos(struct file *f) |
| 1193 | { |
| 1194 | mutex_unlock(&f->f_pos_lock); |
| 1195 | } |
| 1196 | |
| 1197 | /* |
| 1198 | * We only lock f_pos if we have threads or if the file might be |
| 1199 | * shared with another process. In both cases we'll have an elevated |
| 1200 | * file count (done either by fdget() or by fork()). |
| 1201 | */ |
| 1202 | |
| 1203 | void set_close_on_exec(unsigned int fd, int flag) |
| 1204 | { |
| 1205 | struct files_struct *files = current->files; |
| 1206 | struct fdtable *fdt; |
| 1207 | spin_lock(&files->file_lock); |
| 1208 | fdt = files_fdtable(files); |
| 1209 | if (flag) |
| 1210 | __set_close_on_exec(fd, fdt); |
| 1211 | else |
| 1212 | __clear_close_on_exec(fd, fdt); |
| 1213 | spin_unlock(&files->file_lock); |
| 1214 | } |
| 1215 | |
| 1216 | bool get_close_on_exec(unsigned int fd) |
| 1217 | { |
| 1218 | bool res; |
| 1219 | rcu_read_lock(); |
| 1220 | res = close_on_exec(fd, current->files); |
| 1221 | rcu_read_unlock(); |
| 1222 | return res; |
| 1223 | } |
| 1224 | |
| 1225 | static int do_dup2(struct files_struct *files, |
| 1226 | struct file *file, unsigned fd, unsigned flags) |
| 1227 | __releases(&files->file_lock) |
| 1228 | { |
| 1229 | struct file *tofree; |
| 1230 | struct fdtable *fdt; |
| 1231 | |
| 1232 | /* |
| 1233 | * We need to detect attempts to do dup2() over allocated but still |
| 1234 | * not finished descriptor. NB: OpenBSD avoids that at the price of |
| 1235 | * extra work in their equivalent of fget() - they insert struct |
| 1236 | * file immediately after grabbing descriptor, mark it larval if |
| 1237 | * more work (e.g. actual opening) is needed and make sure that |
| 1238 | * fget() treats larval files as absent. Potentially interesting, |
| 1239 | * but while extra work in fget() is trivial, locking implications |
| 1240 | * and amount of surgery on open()-related paths in VFS are not. |
| 1241 | * FreeBSD fails with -EBADF in the same situation, NetBSD "solution" |
| 1242 | * deadlocks in rather amusing ways, AFAICS. All of that is out of |
| 1243 | * scope of POSIX or SUS, since neither considers shared descriptor |
| 1244 | * tables and this condition does not arise without those. |
| 1245 | */ |
| 1246 | fdt = files_fdtable(files); |
| 1247 | fd = array_index_nospec(fd, fdt->max_fds); |
| 1248 | tofree = fdt->fd[fd]; |
| 1249 | if (!tofree && fd_is_open(fd, fdt)) |
| 1250 | goto Ebusy; |
| 1251 | get_file(file); |
| 1252 | rcu_assign_pointer(fdt->fd[fd], file); |
| 1253 | __set_open_fd(fd, fdt); |
| 1254 | if (flags & O_CLOEXEC) |
| 1255 | __set_close_on_exec(fd, fdt); |
| 1256 | else |
| 1257 | __clear_close_on_exec(fd, fdt); |
| 1258 | spin_unlock(&files->file_lock); |
| 1259 | |
| 1260 | if (tofree) |
| 1261 | filp_close(tofree, files); |
| 1262 | |
| 1263 | return fd; |
| 1264 | |
| 1265 | Ebusy: |
| 1266 | spin_unlock(&files->file_lock); |
| 1267 | return -EBUSY; |
| 1268 | } |
| 1269 | |
| 1270 | int replace_fd(unsigned fd, struct file *file, unsigned flags) |
| 1271 | { |
| 1272 | int err; |
| 1273 | struct files_struct *files = current->files; |
| 1274 | |
| 1275 | if (!file) |
| 1276 | return close_fd(fd); |
| 1277 | |
| 1278 | if (fd >= rlimit(RLIMIT_NOFILE)) |
| 1279 | return -EBADF; |
| 1280 | |
| 1281 | spin_lock(&files->file_lock); |
| 1282 | err = expand_files(files, fd); |
| 1283 | if (unlikely(err < 0)) |
| 1284 | goto out_unlock; |
| 1285 | return do_dup2(files, file, fd, flags); |
| 1286 | |
| 1287 | out_unlock: |
| 1288 | spin_unlock(&files->file_lock); |
| 1289 | return err; |
| 1290 | } |
| 1291 | |
| 1292 | /** |
| 1293 | * receive_fd() - Install received file into file descriptor table |
| 1294 | * @file: struct file that was received from another process |
| 1295 | * @ufd: __user pointer to write new fd number to |
| 1296 | * @o_flags: the O_* flags to apply to the new fd entry |
| 1297 | * |
| 1298 | * Installs a received file into the file descriptor table, with appropriate |
| 1299 | * checks and count updates. Optionally writes the fd number to userspace, if |
| 1300 | * @ufd is non-NULL. |
| 1301 | * |
| 1302 | * This helper handles its own reference counting of the incoming |
| 1303 | * struct file. |
| 1304 | * |
| 1305 | * Returns newly install fd or -ve on error. |
| 1306 | */ |
| 1307 | int receive_fd(struct file *file, int __user *ufd, unsigned int o_flags) |
| 1308 | { |
| 1309 | int new_fd; |
| 1310 | int error; |
| 1311 | |
| 1312 | error = security_file_receive(file); |
| 1313 | if (error) |
| 1314 | return error; |
| 1315 | |
| 1316 | new_fd = get_unused_fd_flags(o_flags); |
| 1317 | if (new_fd < 0) |
| 1318 | return new_fd; |
| 1319 | |
| 1320 | if (ufd) { |
| 1321 | error = put_user(new_fd, ufd); |
| 1322 | if (error) { |
| 1323 | put_unused_fd(new_fd); |
| 1324 | return error; |
| 1325 | } |
| 1326 | } |
| 1327 | |
| 1328 | fd_install(new_fd, get_file(file)); |
| 1329 | __receive_sock(file); |
| 1330 | return new_fd; |
| 1331 | } |
| 1332 | EXPORT_SYMBOL_GPL(receive_fd); |
| 1333 | |
| 1334 | int receive_fd_replace(int new_fd, struct file *file, unsigned int o_flags) |
| 1335 | { |
| 1336 | int error; |
| 1337 | |
| 1338 | error = security_file_receive(file); |
| 1339 | if (error) |
| 1340 | return error; |
| 1341 | error = replace_fd(new_fd, file, o_flags); |
| 1342 | if (error) |
| 1343 | return error; |
| 1344 | __receive_sock(file); |
| 1345 | return new_fd; |
| 1346 | } |
| 1347 | |
| 1348 | static int ksys_dup3(unsigned int oldfd, unsigned int newfd, int flags) |
| 1349 | { |
| 1350 | int err = -EBADF; |
| 1351 | struct file *file; |
| 1352 | struct files_struct *files = current->files; |
| 1353 | |
| 1354 | if ((flags & ~O_CLOEXEC) != 0) |
| 1355 | return -EINVAL; |
| 1356 | |
| 1357 | if (unlikely(oldfd == newfd)) |
| 1358 | return -EINVAL; |
| 1359 | |
| 1360 | if (newfd >= rlimit(RLIMIT_NOFILE)) |
| 1361 | return -EBADF; |
| 1362 | |
| 1363 | spin_lock(&files->file_lock); |
| 1364 | err = expand_files(files, newfd); |
| 1365 | file = files_lookup_fd_locked(files, oldfd); |
| 1366 | if (unlikely(!file)) |
| 1367 | goto Ebadf; |
| 1368 | if (unlikely(err < 0)) { |
| 1369 | if (err == -EMFILE) |
| 1370 | goto Ebadf; |
| 1371 | goto out_unlock; |
| 1372 | } |
| 1373 | return do_dup2(files, file, newfd, flags); |
| 1374 | |
| 1375 | Ebadf: |
| 1376 | err = -EBADF; |
| 1377 | out_unlock: |
| 1378 | spin_unlock(&files->file_lock); |
| 1379 | return err; |
| 1380 | } |
| 1381 | |
| 1382 | SYSCALL_DEFINE3(dup3, unsigned int, oldfd, unsigned int, newfd, int, flags) |
| 1383 | { |
| 1384 | return ksys_dup3(oldfd, newfd, flags); |
| 1385 | } |
| 1386 | |
| 1387 | SYSCALL_DEFINE2(dup2, unsigned int, oldfd, unsigned int, newfd) |
| 1388 | { |
| 1389 | if (unlikely(newfd == oldfd)) { /* corner case */ |
| 1390 | struct files_struct *files = current->files; |
| 1391 | struct file *f; |
| 1392 | int retval = oldfd; |
| 1393 | |
| 1394 | rcu_read_lock(); |
| 1395 | f = __fget_files_rcu(files, oldfd, 0); |
| 1396 | if (!f) |
| 1397 | retval = -EBADF; |
| 1398 | rcu_read_unlock(); |
| 1399 | if (f) |
| 1400 | fput(f); |
| 1401 | return retval; |
| 1402 | } |
| 1403 | return ksys_dup3(oldfd, newfd, 0); |
| 1404 | } |
| 1405 | |
| 1406 | SYSCALL_DEFINE1(dup, unsigned int, fildes) |
| 1407 | { |
| 1408 | int ret = -EBADF; |
| 1409 | struct file *file = fget_raw(fildes); |
| 1410 | |
| 1411 | if (file) { |
| 1412 | ret = get_unused_fd_flags(0); |
| 1413 | if (ret >= 0) |
| 1414 | fd_install(ret, file); |
| 1415 | else |
| 1416 | fput(file); |
| 1417 | } |
| 1418 | return ret; |
| 1419 | } |
| 1420 | |
| 1421 | int f_dupfd(unsigned int from, struct file *file, unsigned flags) |
| 1422 | { |
| 1423 | unsigned long nofile = rlimit(RLIMIT_NOFILE); |
| 1424 | int err; |
| 1425 | if (from >= nofile) |
| 1426 | return -EINVAL; |
| 1427 | err = alloc_fd(from, nofile, flags); |
| 1428 | if (err >= 0) { |
| 1429 | get_file(file); |
| 1430 | fd_install(err, file); |
| 1431 | } |
| 1432 | return err; |
| 1433 | } |
| 1434 | |
| 1435 | int iterate_fd(struct files_struct *files, unsigned n, |
| 1436 | int (*f)(const void *, struct file *, unsigned), |
| 1437 | const void *p) |
| 1438 | { |
| 1439 | struct fdtable *fdt; |
| 1440 | int res = 0; |
| 1441 | if (!files) |
| 1442 | return 0; |
| 1443 | spin_lock(&files->file_lock); |
| 1444 | for (fdt = files_fdtable(files); n < fdt->max_fds; n++) { |
| 1445 | struct file *file; |
| 1446 | file = rcu_dereference_check_fdtable(files, fdt->fd[n]); |
| 1447 | if (!file) |
| 1448 | continue; |
| 1449 | res = f(p, file, n); |
| 1450 | if (res) |
| 1451 | break; |
| 1452 | } |
| 1453 | spin_unlock(&files->file_lock); |
| 1454 | return res; |
| 1455 | } |
| 1456 | EXPORT_SYMBOL(iterate_fd); |