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1 | /* |
2 | * linux/fs/fcntl.c |
3 | * |
4 | * Copyright (C) 1991, 1992 Linus Torvalds |
5 | */ |
6 | |
7 | #include <linux/syscalls.h> |
8 | #include <linux/init.h> |
9 | #include <linux/mm.h> |
10 | #include <linux/fs.h> |
11 | #include <linux/file.h> |
12 | #include <linux/fdtable.h> |
13 | #include <linux/capability.h> |
14 | #include <linux/dnotify.h> |
15 | #include <linux/slab.h> |
16 | #include <linux/module.h> |
17 | #include <linux/pipe_fs_i.h> |
18 | #include <linux/security.h> |
19 | #include <linux/ptrace.h> |
20 | #include <linux/signal.h> |
21 | #include <linux/rcupdate.h> |
22 | #include <linux/pid_namespace.h> |
23 | #include <linux/user_namespace.h> |
24 | |
25 | #include <asm/poll.h> |
26 | #include <asm/siginfo.h> |
27 | #include <asm/uaccess.h> |
28 | |
29 | void set_close_on_exec(unsigned int fd, int flag) |
30 | { |
31 | struct files_struct *files = current->files; |
32 | struct fdtable *fdt; |
33 | spin_lock(&files->file_lock); |
34 | fdt = files_fdtable(files); |
35 | if (flag) |
36 | __set_close_on_exec(fd, fdt); |
37 | else |
38 | __clear_close_on_exec(fd, fdt); |
39 | spin_unlock(&files->file_lock); |
40 | } |
41 | |
42 | static bool get_close_on_exec(unsigned int fd) |
43 | { |
44 | struct files_struct *files = current->files; |
45 | struct fdtable *fdt; |
46 | bool res; |
47 | rcu_read_lock(); |
48 | fdt = files_fdtable(files); |
49 | res = close_on_exec(fd, fdt); |
50 | rcu_read_unlock(); |
51 | return res; |
52 | } |
53 | |
54 | SYSCALL_DEFINE3(dup3, unsigned int, oldfd, unsigned int, newfd, int, flags) |
55 | { |
56 | int err = -EBADF; |
57 | struct file * file, *tofree; |
58 | struct files_struct * files = current->files; |
59 | struct fdtable *fdt; |
60 | |
61 | if ((flags & ~O_CLOEXEC) != 0) |
62 | return -EINVAL; |
63 | |
64 | if (unlikely(oldfd == newfd)) |
65 | return -EINVAL; |
66 | |
67 | spin_lock(&files->file_lock); |
68 | err = expand_files(files, newfd); |
69 | file = fcheck(oldfd); |
70 | if (unlikely(!file)) |
71 | goto Ebadf; |
72 | if (unlikely(err < 0)) { |
73 | if (err == -EMFILE) |
74 | goto Ebadf; |
75 | goto out_unlock; |
76 | } |
77 | /* |
78 | * We need to detect attempts to do dup2() over allocated but still |
79 | * not finished descriptor. NB: OpenBSD avoids that at the price of |
80 | * extra work in their equivalent of fget() - they insert struct |
81 | * file immediately after grabbing descriptor, mark it larval if |
82 | * more work (e.g. actual opening) is needed and make sure that |
83 | * fget() treats larval files as absent. Potentially interesting, |
84 | * but while extra work in fget() is trivial, locking implications |
85 | * and amount of surgery on open()-related paths in VFS are not. |
86 | * FreeBSD fails with -EBADF in the same situation, NetBSD "solution" |
87 | * deadlocks in rather amusing ways, AFAICS. All of that is out of |
88 | * scope of POSIX or SUS, since neither considers shared descriptor |
89 | * tables and this condition does not arise without those. |
90 | */ |
91 | err = -EBUSY; |
92 | fdt = files_fdtable(files); |
93 | tofree = fdt->fd[newfd]; |
94 | if (!tofree && fd_is_open(newfd, fdt)) |
95 | goto out_unlock; |
96 | get_file(file); |
97 | rcu_assign_pointer(fdt->fd[newfd], file); |
98 | __set_open_fd(newfd, fdt); |
99 | if (flags & O_CLOEXEC) |
100 | __set_close_on_exec(newfd, fdt); |
101 | else |
102 | __clear_close_on_exec(newfd, fdt); |
103 | spin_unlock(&files->file_lock); |
104 | |
105 | if (tofree) |
106 | filp_close(tofree, files); |
107 | |
108 | return newfd; |
109 | |
110 | Ebadf: |
111 | err = -EBADF; |
112 | out_unlock: |
113 | spin_unlock(&files->file_lock); |
114 | return err; |
115 | } |
116 | |
117 | SYSCALL_DEFINE2(dup2, unsigned int, oldfd, unsigned int, newfd) |
118 | { |
119 | if (unlikely(newfd == oldfd)) { /* corner case */ |
120 | struct files_struct *files = current->files; |
121 | int retval = oldfd; |
122 | |
123 | rcu_read_lock(); |
124 | if (!fcheck_files(files, oldfd)) |
125 | retval = -EBADF; |
126 | rcu_read_unlock(); |
127 | return retval; |
128 | } |
129 | return sys_dup3(oldfd, newfd, 0); |
130 | } |
131 | |
132 | SYSCALL_DEFINE1(dup, unsigned int, fildes) |
133 | { |
134 | int ret = -EBADF; |
135 | struct file *file = fget_raw(fildes); |
136 | |
137 | if (file) { |
138 | ret = get_unused_fd(); |
139 | if (ret >= 0) |
140 | fd_install(ret, file); |
141 | else |
142 | fput(file); |
143 | } |
144 | return ret; |
145 | } |
146 | |
147 | #define SETFL_MASK (O_APPEND | O_NONBLOCK | O_NDELAY | O_DIRECT | O_NOATIME) |
148 | |
149 | static int setfl(int fd, struct file * filp, unsigned long arg) |
150 | { |
151 | struct inode * inode = filp->f_path.dentry->d_inode; |
152 | int error = 0; |
153 | |
154 | /* |
155 | * O_APPEND cannot be cleared if the file is marked as append-only |
156 | * and the file is open for write. |
157 | */ |
158 | if (((arg ^ filp->f_flags) & O_APPEND) && IS_APPEND(inode)) |
159 | return -EPERM; |
160 | |
161 | /* O_NOATIME can only be set by the owner or superuser */ |
162 | if ((arg & O_NOATIME) && !(filp->f_flags & O_NOATIME)) |
163 | if (!inode_owner_or_capable(inode)) |
164 | return -EPERM; |
165 | |
166 | /* required for strict SunOS emulation */ |
167 | if (O_NONBLOCK != O_NDELAY) |
168 | if (arg & O_NDELAY) |
169 | arg |= O_NONBLOCK; |
170 | |
171 | if (arg & O_DIRECT) { |
172 | if (!filp->f_mapping || !filp->f_mapping->a_ops || |
173 | !filp->f_mapping->a_ops->direct_IO) |
174 | return -EINVAL; |
175 | } |
176 | |
177 | if (filp->f_op && filp->f_op->check_flags) |
178 | error = filp->f_op->check_flags(arg); |
179 | if (error) |
180 | return error; |
181 | |
182 | /* |
183 | * ->fasync() is responsible for setting the FASYNC bit. |
184 | */ |
185 | if (((arg ^ filp->f_flags) & FASYNC) && filp->f_op && |
186 | filp->f_op->fasync) { |
187 | error = filp->f_op->fasync(fd, filp, (arg & FASYNC) != 0); |
188 | if (error < 0) |
189 | goto out; |
190 | if (error > 0) |
191 | error = 0; |
192 | } |
193 | spin_lock(&filp->f_lock); |
194 | filp->f_flags = (arg & SETFL_MASK) | (filp->f_flags & ~SETFL_MASK); |
195 | spin_unlock(&filp->f_lock); |
196 | |
197 | out: |
198 | return error; |
199 | } |
200 | |
201 | static void f_modown(struct file *filp, struct pid *pid, enum pid_type type, |
202 | int force) |
203 | { |
204 | write_lock_irq(&filp->f_owner.lock); |
205 | if (force || !filp->f_owner.pid) { |
206 | put_pid(filp->f_owner.pid); |
207 | filp->f_owner.pid = get_pid(pid); |
208 | filp->f_owner.pid_type = type; |
209 | |
210 | if (pid) { |
211 | const struct cred *cred = current_cred(); |
212 | filp->f_owner.uid = cred->uid; |
213 | filp->f_owner.euid = cred->euid; |
214 | } |
215 | } |
216 | write_unlock_irq(&filp->f_owner.lock); |
217 | } |
218 | |
219 | int __f_setown(struct file *filp, struct pid *pid, enum pid_type type, |
220 | int force) |
221 | { |
222 | int err; |
223 | |
224 | err = security_file_set_fowner(filp); |
225 | if (err) |
226 | return err; |
227 | |
228 | f_modown(filp, pid, type, force); |
229 | return 0; |
230 | } |
231 | EXPORT_SYMBOL(__f_setown); |
232 | |
233 | int f_setown(struct file *filp, unsigned long arg, int force) |
234 | { |
235 | enum pid_type type; |
236 | struct pid *pid; |
237 | int who = arg; |
238 | int result; |
239 | type = PIDTYPE_PID; |
240 | if (who < 0) { |
241 | type = PIDTYPE_PGID; |
242 | who = -who; |
243 | } |
244 | rcu_read_lock(); |
245 | pid = find_vpid(who); |
246 | result = __f_setown(filp, pid, type, force); |
247 | rcu_read_unlock(); |
248 | return result; |
249 | } |
250 | EXPORT_SYMBOL(f_setown); |
251 | |
252 | void f_delown(struct file *filp) |
253 | { |
254 | f_modown(filp, NULL, PIDTYPE_PID, 1); |
255 | } |
256 | |
257 | pid_t f_getown(struct file *filp) |
258 | { |
259 | pid_t pid; |
260 | read_lock(&filp->f_owner.lock); |
261 | pid = pid_vnr(filp->f_owner.pid); |
262 | if (filp->f_owner.pid_type == PIDTYPE_PGID) |
263 | pid = -pid; |
264 | read_unlock(&filp->f_owner.lock); |
265 | return pid; |
266 | } |
267 | |
268 | static int f_setown_ex(struct file *filp, unsigned long arg) |
269 | { |
270 | struct f_owner_ex * __user owner_p = (void * __user)arg; |
271 | struct f_owner_ex owner; |
272 | struct pid *pid; |
273 | int type; |
274 | int ret; |
275 | |
276 | ret = copy_from_user(&owner, owner_p, sizeof(owner)); |
277 | if (ret) |
278 | return -EFAULT; |
279 | |
280 | switch (owner.type) { |
281 | case F_OWNER_TID: |
282 | type = PIDTYPE_MAX; |
283 | break; |
284 | |
285 | case F_OWNER_PID: |
286 | type = PIDTYPE_PID; |
287 | break; |
288 | |
289 | case F_OWNER_PGRP: |
290 | type = PIDTYPE_PGID; |
291 | break; |
292 | |
293 | default: |
294 | return -EINVAL; |
295 | } |
296 | |
297 | rcu_read_lock(); |
298 | pid = find_vpid(owner.pid); |
299 | if (owner.pid && !pid) |
300 | ret = -ESRCH; |
301 | else |
302 | ret = __f_setown(filp, pid, type, 1); |
303 | rcu_read_unlock(); |
304 | |
305 | return ret; |
306 | } |
307 | |
308 | static int f_getown_ex(struct file *filp, unsigned long arg) |
309 | { |
310 | struct f_owner_ex * __user owner_p = (void * __user)arg; |
311 | struct f_owner_ex owner; |
312 | int ret = 0; |
313 | |
314 | read_lock(&filp->f_owner.lock); |
315 | owner.pid = pid_vnr(filp->f_owner.pid); |
316 | switch (filp->f_owner.pid_type) { |
317 | case PIDTYPE_MAX: |
318 | owner.type = F_OWNER_TID; |
319 | break; |
320 | |
321 | case PIDTYPE_PID: |
322 | owner.type = F_OWNER_PID; |
323 | break; |
324 | |
325 | case PIDTYPE_PGID: |
326 | owner.type = F_OWNER_PGRP; |
327 | break; |
328 | |
329 | default: |
330 | WARN_ON(1); |
331 | ret = -EINVAL; |
332 | break; |
333 | } |
334 | read_unlock(&filp->f_owner.lock); |
335 | |
336 | if (!ret) { |
337 | ret = copy_to_user(owner_p, &owner, sizeof(owner)); |
338 | if (ret) |
339 | ret = -EFAULT; |
340 | } |
341 | return ret; |
342 | } |
343 | |
344 | #ifdef CONFIG_CHECKPOINT_RESTORE |
345 | static int f_getowner_uids(struct file *filp, unsigned long arg) |
346 | { |
347 | struct user_namespace *user_ns = current_user_ns(); |
348 | uid_t * __user dst = (void * __user)arg; |
349 | uid_t src[2]; |
350 | int err; |
351 | |
352 | read_lock(&filp->f_owner.lock); |
353 | src[0] = from_kuid(user_ns, filp->f_owner.uid); |
354 | src[1] = from_kuid(user_ns, filp->f_owner.euid); |
355 | read_unlock(&filp->f_owner.lock); |
356 | |
357 | err = put_user(src[0], &dst[0]); |
358 | err |= put_user(src[1], &dst[1]); |
359 | |
360 | return err; |
361 | } |
362 | #else |
363 | static int f_getowner_uids(struct file *filp, unsigned long arg) |
364 | { |
365 | return -EINVAL; |
366 | } |
367 | #endif |
368 | |
369 | static long do_fcntl(int fd, unsigned int cmd, unsigned long arg, |
370 | struct file *filp) |
371 | { |
372 | long err = -EINVAL; |
373 | |
374 | switch (cmd) { |
375 | case F_DUPFD: |
376 | case F_DUPFD_CLOEXEC: |
377 | if (arg >= rlimit(RLIMIT_NOFILE)) |
378 | break; |
379 | err = alloc_fd(arg, cmd == F_DUPFD_CLOEXEC ? O_CLOEXEC : 0); |
380 | if (err >= 0) { |
381 | get_file(filp); |
382 | fd_install(err, filp); |
383 | } |
384 | break; |
385 | case F_GETFD: |
386 | err = get_close_on_exec(fd) ? FD_CLOEXEC : 0; |
387 | break; |
388 | case F_SETFD: |
389 | err = 0; |
390 | set_close_on_exec(fd, arg & FD_CLOEXEC); |
391 | break; |
392 | case F_GETFL: |
393 | err = filp->f_flags; |
394 | break; |
395 | case F_SETFL: |
396 | err = setfl(fd, filp, arg); |
397 | break; |
398 | case F_GETLK: |
399 | err = fcntl_getlk(filp, (struct flock __user *) arg); |
400 | break; |
401 | case F_SETLK: |
402 | case F_SETLKW: |
403 | err = fcntl_setlk(fd, filp, cmd, (struct flock __user *) arg); |
404 | break; |
405 | case F_GETOWN: |
406 | /* |
407 | * XXX If f_owner is a process group, the |
408 | * negative return value will get converted |
409 | * into an error. Oops. If we keep the |
410 | * current syscall conventions, the only way |
411 | * to fix this will be in libc. |
412 | */ |
413 | err = f_getown(filp); |
414 | force_successful_syscall_return(); |
415 | break; |
416 | case F_SETOWN: |
417 | err = f_setown(filp, arg, 1); |
418 | break; |
419 | case F_GETOWN_EX: |
420 | err = f_getown_ex(filp, arg); |
421 | break; |
422 | case F_SETOWN_EX: |
423 | err = f_setown_ex(filp, arg); |
424 | break; |
425 | case F_GETOWNER_UIDS: |
426 | err = f_getowner_uids(filp, arg); |
427 | break; |
428 | case F_GETSIG: |
429 | err = filp->f_owner.signum; |
430 | break; |
431 | case F_SETSIG: |
432 | /* arg == 0 restores default behaviour. */ |
433 | if (!valid_signal(arg)) { |
434 | break; |
435 | } |
436 | err = 0; |
437 | filp->f_owner.signum = arg; |
438 | break; |
439 | case F_GETLEASE: |
440 | err = fcntl_getlease(filp); |
441 | break; |
442 | case F_SETLEASE: |
443 | err = fcntl_setlease(fd, filp, arg); |
444 | break; |
445 | case F_NOTIFY: |
446 | err = fcntl_dirnotify(fd, filp, arg); |
447 | break; |
448 | case F_SETPIPE_SZ: |
449 | case F_GETPIPE_SZ: |
450 | err = pipe_fcntl(filp, cmd, arg); |
451 | break; |
452 | default: |
453 | break; |
454 | } |
455 | return err; |
456 | } |
457 | |
458 | static int check_fcntl_cmd(unsigned cmd) |
459 | { |
460 | switch (cmd) { |
461 | case F_DUPFD: |
462 | case F_DUPFD_CLOEXEC: |
463 | case F_GETFD: |
464 | case F_SETFD: |
465 | case F_GETFL: |
466 | return 1; |
467 | } |
468 | return 0; |
469 | } |
470 | |
471 | SYSCALL_DEFINE3(fcntl, unsigned int, fd, unsigned int, cmd, unsigned long, arg) |
472 | { |
473 | struct file *filp; |
474 | int fput_needed; |
475 | long err = -EBADF; |
476 | |
477 | filp = fget_raw_light(fd, &fput_needed); |
478 | if (!filp) |
479 | goto out; |
480 | |
481 | if (unlikely(filp->f_mode & FMODE_PATH)) { |
482 | if (!check_fcntl_cmd(cmd)) |
483 | goto out1; |
484 | } |
485 | |
486 | err = security_file_fcntl(filp, cmd, arg); |
487 | if (!err) |
488 | err = do_fcntl(fd, cmd, arg, filp); |
489 | |
490 | out1: |
491 | fput_light(filp, fput_needed); |
492 | out: |
493 | return err; |
494 | } |
495 | |
496 | #if BITS_PER_LONG == 32 |
497 | SYSCALL_DEFINE3(fcntl64, unsigned int, fd, unsigned int, cmd, |
498 | unsigned long, arg) |
499 | { |
500 | struct file * filp; |
501 | long err = -EBADF; |
502 | int fput_needed; |
503 | |
504 | filp = fget_raw_light(fd, &fput_needed); |
505 | if (!filp) |
506 | goto out; |
507 | |
508 | if (unlikely(filp->f_mode & FMODE_PATH)) { |
509 | if (!check_fcntl_cmd(cmd)) |
510 | goto out1; |
511 | } |
512 | |
513 | err = security_file_fcntl(filp, cmd, arg); |
514 | if (err) |
515 | goto out1; |
516 | |
517 | switch (cmd) { |
518 | case F_GETLK64: |
519 | err = fcntl_getlk64(filp, (struct flock64 __user *) arg); |
520 | break; |
521 | case F_SETLK64: |
522 | case F_SETLKW64: |
523 | err = fcntl_setlk64(fd, filp, cmd, |
524 | (struct flock64 __user *) arg); |
525 | break; |
526 | default: |
527 | err = do_fcntl(fd, cmd, arg, filp); |
528 | break; |
529 | } |
530 | out1: |
531 | fput_light(filp, fput_needed); |
532 | out: |
533 | return err; |
534 | } |
535 | #endif |
536 | |
537 | /* Table to convert sigio signal codes into poll band bitmaps */ |
538 | |
539 | static const long band_table[NSIGPOLL] = { |
540 | POLLIN | POLLRDNORM, /* POLL_IN */ |
541 | POLLOUT | POLLWRNORM | POLLWRBAND, /* POLL_OUT */ |
542 | POLLIN | POLLRDNORM | POLLMSG, /* POLL_MSG */ |
543 | POLLERR, /* POLL_ERR */ |
544 | POLLPRI | POLLRDBAND, /* POLL_PRI */ |
545 | POLLHUP | POLLERR /* POLL_HUP */ |
546 | }; |
547 | |
548 | static inline int sigio_perm(struct task_struct *p, |
549 | struct fown_struct *fown, int sig) |
550 | { |
551 | const struct cred *cred; |
552 | int ret; |
553 | |
554 | rcu_read_lock(); |
555 | cred = __task_cred(p); |
556 | ret = ((uid_eq(fown->euid, GLOBAL_ROOT_UID) || |
557 | uid_eq(fown->euid, cred->suid) || uid_eq(fown->euid, cred->uid) || |
558 | uid_eq(fown->uid, cred->suid) || uid_eq(fown->uid, cred->uid)) && |
559 | !security_file_send_sigiotask(p, fown, sig)); |
560 | rcu_read_unlock(); |
561 | return ret; |
562 | } |
563 | |
564 | static void send_sigio_to_task(struct task_struct *p, |
565 | struct fown_struct *fown, |
566 | int fd, int reason, int group) |
567 | { |
568 | /* |
569 | * F_SETSIG can change ->signum lockless in parallel, make |
570 | * sure we read it once and use the same value throughout. |
571 | */ |
572 | int signum = ACCESS_ONCE(fown->signum); |
573 | |
574 | if (!sigio_perm(p, fown, signum)) |
575 | return; |
576 | |
577 | switch (signum) { |
578 | siginfo_t si; |
579 | default: |
580 | /* Queue a rt signal with the appropriate fd as its |
581 | value. We use SI_SIGIO as the source, not |
582 | SI_KERNEL, since kernel signals always get |
583 | delivered even if we can't queue. Failure to |
584 | queue in this case _should_ be reported; we fall |
585 | back to SIGIO in that case. --sct */ |
586 | si.si_signo = signum; |
587 | si.si_errno = 0; |
588 | si.si_code = reason; |
589 | /* Make sure we are called with one of the POLL_* |
590 | reasons, otherwise we could leak kernel stack into |
591 | userspace. */ |
592 | BUG_ON((reason & __SI_MASK) != __SI_POLL); |
593 | if (reason - POLL_IN >= NSIGPOLL) |
594 | si.si_band = ~0L; |
595 | else |
596 | si.si_band = band_table[reason - POLL_IN]; |
597 | si.si_fd = fd; |
598 | if (!do_send_sig_info(signum, &si, p, group)) |
599 | break; |
600 | /* fall-through: fall back on the old plain SIGIO signal */ |
601 | case 0: |
602 | do_send_sig_info(SIGIO, SEND_SIG_PRIV, p, group); |
603 | } |
604 | } |
605 | |
606 | void send_sigio(struct fown_struct *fown, int fd, int band) |
607 | { |
608 | struct task_struct *p; |
609 | enum pid_type type; |
610 | struct pid *pid; |
611 | int group = 1; |
612 | |
613 | read_lock(&fown->lock); |
614 | |
615 | type = fown->pid_type; |
616 | if (type == PIDTYPE_MAX) { |
617 | group = 0; |
618 | type = PIDTYPE_PID; |
619 | } |
620 | |
621 | pid = fown->pid; |
622 | if (!pid) |
623 | goto out_unlock_fown; |
624 | |
625 | read_lock(&tasklist_lock); |
626 | do_each_pid_task(pid, type, p) { |
627 | send_sigio_to_task(p, fown, fd, band, group); |
628 | } while_each_pid_task(pid, type, p); |
629 | read_unlock(&tasklist_lock); |
630 | out_unlock_fown: |
631 | read_unlock(&fown->lock); |
632 | } |
633 | |
634 | static void send_sigurg_to_task(struct task_struct *p, |
635 | struct fown_struct *fown, int group) |
636 | { |
637 | if (sigio_perm(p, fown, SIGURG)) |
638 | do_send_sig_info(SIGURG, SEND_SIG_PRIV, p, group); |
639 | } |
640 | |
641 | int send_sigurg(struct fown_struct *fown) |
642 | { |
643 | struct task_struct *p; |
644 | enum pid_type type; |
645 | struct pid *pid; |
646 | int group = 1; |
647 | int ret = 0; |
648 | |
649 | read_lock(&fown->lock); |
650 | |
651 | type = fown->pid_type; |
652 | if (type == PIDTYPE_MAX) { |
653 | group = 0; |
654 | type = PIDTYPE_PID; |
655 | } |
656 | |
657 | pid = fown->pid; |
658 | if (!pid) |
659 | goto out_unlock_fown; |
660 | |
661 | ret = 1; |
662 | |
663 | read_lock(&tasklist_lock); |
664 | do_each_pid_task(pid, type, p) { |
665 | send_sigurg_to_task(p, fown, group); |
666 | } while_each_pid_task(pid, type, p); |
667 | read_unlock(&tasklist_lock); |
668 | out_unlock_fown: |
669 | read_unlock(&fown->lock); |
670 | return ret; |
671 | } |
672 | |
673 | static DEFINE_SPINLOCK(fasync_lock); |
674 | static struct kmem_cache *fasync_cache __read_mostly; |
675 | |
676 | static void fasync_free_rcu(struct rcu_head *head) |
677 | { |
678 | kmem_cache_free(fasync_cache, |
679 | container_of(head, struct fasync_struct, fa_rcu)); |
680 | } |
681 | |
682 | /* |
683 | * Remove a fasync entry. If successfully removed, return |
684 | * positive and clear the FASYNC flag. If no entry exists, |
685 | * do nothing and return 0. |
686 | * |
687 | * NOTE! It is very important that the FASYNC flag always |
688 | * match the state "is the filp on a fasync list". |
689 | * |
690 | */ |
691 | int fasync_remove_entry(struct file *filp, struct fasync_struct **fapp) |
692 | { |
693 | struct fasync_struct *fa, **fp; |
694 | int result = 0; |
695 | |
696 | spin_lock(&filp->f_lock); |
697 | spin_lock(&fasync_lock); |
698 | for (fp = fapp; (fa = *fp) != NULL; fp = &fa->fa_next) { |
699 | if (fa->fa_file != filp) |
700 | continue; |
701 | |
702 | spin_lock_irq(&fa->fa_lock); |
703 | fa->fa_file = NULL; |
704 | spin_unlock_irq(&fa->fa_lock); |
705 | |
706 | *fp = fa->fa_next; |
707 | call_rcu(&fa->fa_rcu, fasync_free_rcu); |
708 | filp->f_flags &= ~FASYNC; |
709 | result = 1; |
710 | break; |
711 | } |
712 | spin_unlock(&fasync_lock); |
713 | spin_unlock(&filp->f_lock); |
714 | return result; |
715 | } |
716 | |
717 | struct fasync_struct *fasync_alloc(void) |
718 | { |
719 | return kmem_cache_alloc(fasync_cache, GFP_KERNEL); |
720 | } |
721 | |
722 | /* |
723 | * NOTE! This can be used only for unused fasync entries: |
724 | * entries that actually got inserted on the fasync list |
725 | * need to be released by rcu - see fasync_remove_entry. |
726 | */ |
727 | void fasync_free(struct fasync_struct *new) |
728 | { |
729 | kmem_cache_free(fasync_cache, new); |
730 | } |
731 | |
732 | /* |
733 | * Insert a new entry into the fasync list. Return the pointer to the |
734 | * old one if we didn't use the new one. |
735 | * |
736 | * NOTE! It is very important that the FASYNC flag always |
737 | * match the state "is the filp on a fasync list". |
738 | */ |
739 | struct fasync_struct *fasync_insert_entry(int fd, struct file *filp, struct fasync_struct **fapp, struct fasync_struct *new) |
740 | { |
741 | struct fasync_struct *fa, **fp; |
742 | |
743 | spin_lock(&filp->f_lock); |
744 | spin_lock(&fasync_lock); |
745 | for (fp = fapp; (fa = *fp) != NULL; fp = &fa->fa_next) { |
746 | if (fa->fa_file != filp) |
747 | continue; |
748 | |
749 | spin_lock_irq(&fa->fa_lock); |
750 | fa->fa_fd = fd; |
751 | spin_unlock_irq(&fa->fa_lock); |
752 | goto out; |
753 | } |
754 | |
755 | spin_lock_init(&new->fa_lock); |
756 | new->magic = FASYNC_MAGIC; |
757 | new->fa_file = filp; |
758 | new->fa_fd = fd; |
759 | new->fa_next = *fapp; |
760 | rcu_assign_pointer(*fapp, new); |
761 | filp->f_flags |= FASYNC; |
762 | |
763 | out: |
764 | spin_unlock(&fasync_lock); |
765 | spin_unlock(&filp->f_lock); |
766 | return fa; |
767 | } |
768 | |
769 | /* |
770 | * Add a fasync entry. Return negative on error, positive if |
771 | * added, and zero if did nothing but change an existing one. |
772 | */ |
773 | static int fasync_add_entry(int fd, struct file *filp, struct fasync_struct **fapp) |
774 | { |
775 | struct fasync_struct *new; |
776 | |
777 | new = fasync_alloc(); |
778 | if (!new) |
779 | return -ENOMEM; |
780 | |
781 | /* |
782 | * fasync_insert_entry() returns the old (update) entry if |
783 | * it existed. |
784 | * |
785 | * So free the (unused) new entry and return 0 to let the |
786 | * caller know that we didn't add any new fasync entries. |
787 | */ |
788 | if (fasync_insert_entry(fd, filp, fapp, new)) { |
789 | fasync_free(new); |
790 | return 0; |
791 | } |
792 | |
793 | return 1; |
794 | } |
795 | |
796 | /* |
797 | * fasync_helper() is used by almost all character device drivers |
798 | * to set up the fasync queue, and for regular files by the file |
799 | * lease code. It returns negative on error, 0 if it did no changes |
800 | * and positive if it added/deleted the entry. |
801 | */ |
802 | int fasync_helper(int fd, struct file * filp, int on, struct fasync_struct **fapp) |
803 | { |
804 | if (!on) |
805 | return fasync_remove_entry(filp, fapp); |
806 | return fasync_add_entry(fd, filp, fapp); |
807 | } |
808 | |
809 | EXPORT_SYMBOL(fasync_helper); |
810 | |
811 | /* |
812 | * rcu_read_lock() is held |
813 | */ |
814 | static void kill_fasync_rcu(struct fasync_struct *fa, int sig, int band) |
815 | { |
816 | while (fa) { |
817 | struct fown_struct *fown; |
818 | unsigned long flags; |
819 | |
820 | if (fa->magic != FASYNC_MAGIC) { |
821 | printk(KERN_ERR "kill_fasync: bad magic number in " |
822 | "fasync_struct!\n"); |
823 | return; |
824 | } |
825 | spin_lock_irqsave(&fa->fa_lock, flags); |
826 | if (fa->fa_file) { |
827 | fown = &fa->fa_file->f_owner; |
828 | /* Don't send SIGURG to processes which have not set a |
829 | queued signum: SIGURG has its own default signalling |
830 | mechanism. */ |
831 | if (!(sig == SIGURG && fown->signum == 0)) |
832 | send_sigio(fown, fa->fa_fd, band); |
833 | } |
834 | spin_unlock_irqrestore(&fa->fa_lock, flags); |
835 | fa = rcu_dereference(fa->fa_next); |
836 | } |
837 | } |
838 | |
839 | void kill_fasync(struct fasync_struct **fp, int sig, int band) |
840 | { |
841 | /* First a quick test without locking: usually |
842 | * the list is empty. |
843 | */ |
844 | if (*fp) { |
845 | rcu_read_lock(); |
846 | kill_fasync_rcu(rcu_dereference(*fp), sig, band); |
847 | rcu_read_unlock(); |
848 | } |
849 | } |
850 | EXPORT_SYMBOL(kill_fasync); |
851 | |
852 | static int __init fcntl_init(void) |
853 | { |
854 | /* |
855 | * Please add new bits here to ensure allocation uniqueness. |
856 | * Exceptions: O_NONBLOCK is a two bit define on parisc; O_NDELAY |
857 | * is defined as O_NONBLOCK on some platforms and not on others. |
858 | */ |
859 | BUILD_BUG_ON(19 - 1 /* for O_RDONLY being 0 */ != HWEIGHT32( |
860 | O_RDONLY | O_WRONLY | O_RDWR | |
861 | O_CREAT | O_EXCL | O_NOCTTY | |
862 | O_TRUNC | O_APPEND | /* O_NONBLOCK | */ |
863 | __O_SYNC | O_DSYNC | FASYNC | |
864 | O_DIRECT | O_LARGEFILE | O_DIRECTORY | |
865 | O_NOFOLLOW | O_NOATIME | O_CLOEXEC | |
866 | __FMODE_EXEC | O_PATH |
867 | )); |
868 | |
869 | fasync_cache = kmem_cache_create("fasync_cache", |
870 | sizeof(struct fasync_struct), 0, SLAB_PANIC, NULL); |
871 | return 0; |
872 | } |
873 | |
874 | module_init(fcntl_init) |
875 |
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