1// SPDX-License-Identifier: GPL-2.0
2/*
3 * linux/fs/fcntl.c
4 *
5 * Copyright (C) 1991, 1992 Linus Torvalds
6 */
7
8#include <linux/syscalls.h>
9#include <linux/init.h>
10#include <linux/mm.h>
11#include <linux/sched/task.h>
12#include <linux/fs.h>
13#include <linux/filelock.h>
14#include <linux/file.h>
15#include <linux/fdtable.h>
16#include <linux/capability.h>
17#include <linux/dnotify.h>
18#include <linux/slab.h>
19#include <linux/module.h>
20#include <linux/pipe_fs_i.h>
21#include <linux/security.h>
22#include <linux/ptrace.h>
23#include <linux/signal.h>
24#include <linux/rcupdate.h>
25#include <linux/pid_namespace.h>
26#include <linux/user_namespace.h>
27#include <linux/memfd.h>
28#include <linux/compat.h>
29#include <linux/mount.h>
30
31#include <linux/poll.h>
32#include <asm/siginfo.h>
33#include <linux/uaccess.h>
34
35#define SETFL_MASK (O_APPEND | O_NONBLOCK | O_NDELAY | O_DIRECT | O_NOATIME)
36
37static int setfl(int fd, struct file * filp, unsigned int arg)
38{
39 struct inode * inode = file_inode(f: filp);
40 int error = 0;
41
42 /*
43 * O_APPEND cannot be cleared if the file is marked as append-only
44 * and the file is open for write.
45 */
46 if (((arg ^ filp->f_flags) & O_APPEND) && IS_APPEND(inode))
47 return -EPERM;
48
49 /* O_NOATIME can only be set by the owner or superuser */
50 if ((arg & O_NOATIME) && !(filp->f_flags & O_NOATIME))
51 if (!inode_owner_or_capable(idmap: file_mnt_idmap(file: filp), inode))
52 return -EPERM;
53
54 /* required for strict SunOS emulation */
55 if (O_NONBLOCK != O_NDELAY)
56 if (arg & O_NDELAY)
57 arg |= O_NONBLOCK;
58
59 /* Pipe packetized mode is controlled by O_DIRECT flag */
60 if (!S_ISFIFO(inode->i_mode) &&
61 (arg & O_DIRECT) &&
62 !(filp->f_mode & FMODE_CAN_ODIRECT))
63 return -EINVAL;
64
65 if (filp->f_op->check_flags)
66 error = filp->f_op->check_flags(arg);
67 if (error)
68 return error;
69
70 /*
71 * ->fasync() is responsible for setting the FASYNC bit.
72 */
73 if (((arg ^ filp->f_flags) & FASYNC) && filp->f_op->fasync) {
74 error = filp->f_op->fasync(fd, filp, (arg & FASYNC) != 0);
75 if (error < 0)
76 goto out;
77 if (error > 0)
78 error = 0;
79 }
80 spin_lock(lock: &filp->f_lock);
81 filp->f_flags = (arg & SETFL_MASK) | (filp->f_flags & ~SETFL_MASK);
82 filp->f_iocb_flags = iocb_flags(file: filp);
83 spin_unlock(lock: &filp->f_lock);
84
85 out:
86 return error;
87}
88
89static void f_modown(struct file *filp, struct pid *pid, enum pid_type type,
90 int force)
91{
92 write_lock_irq(&filp->f_owner.lock);
93 if (force || !filp->f_owner.pid) {
94 put_pid(pid: filp->f_owner.pid);
95 filp->f_owner.pid = get_pid(pid);
96 filp->f_owner.pid_type = type;
97
98 if (pid) {
99 const struct cred *cred = current_cred();
100 filp->f_owner.uid = cred->uid;
101 filp->f_owner.euid = cred->euid;
102 }
103 }
104 write_unlock_irq(&filp->f_owner.lock);
105}
106
107void __f_setown(struct file *filp, struct pid *pid, enum pid_type type,
108 int force)
109{
110 security_file_set_fowner(file: filp);
111 f_modown(filp, pid, type, force);
112}
113EXPORT_SYMBOL(__f_setown);
114
115int f_setown(struct file *filp, int who, int force)
116{
117 enum pid_type type;
118 struct pid *pid = NULL;
119 int ret = 0;
120
121 type = PIDTYPE_TGID;
122 if (who < 0) {
123 /* avoid overflow below */
124 if (who == INT_MIN)
125 return -EINVAL;
126
127 type = PIDTYPE_PGID;
128 who = -who;
129 }
130
131 rcu_read_lock();
132 if (who) {
133 pid = find_vpid(nr: who);
134 if (!pid)
135 ret = -ESRCH;
136 }
137
138 if (!ret)
139 __f_setown(filp, pid, type, force);
140 rcu_read_unlock();
141
142 return ret;
143}
144EXPORT_SYMBOL(f_setown);
145
146void f_delown(struct file *filp)
147{
148 f_modown(filp, NULL, type: PIDTYPE_TGID, force: 1);
149}
150
151pid_t f_getown(struct file *filp)
152{
153 pid_t pid = 0;
154
155 read_lock_irq(&filp->f_owner.lock);
156 rcu_read_lock();
157 if (pid_task(pid: filp->f_owner.pid, filp->f_owner.pid_type)) {
158 pid = pid_vnr(pid: filp->f_owner.pid);
159 if (filp->f_owner.pid_type == PIDTYPE_PGID)
160 pid = -pid;
161 }
162 rcu_read_unlock();
163 read_unlock_irq(&filp->f_owner.lock);
164 return pid;
165}
166
167static int f_setown_ex(struct file *filp, unsigned long arg)
168{
169 struct f_owner_ex __user *owner_p = (void __user *)arg;
170 struct f_owner_ex owner;
171 struct pid *pid;
172 int type;
173 int ret;
174
175 ret = copy_from_user(to: &owner, from: owner_p, n: sizeof(owner));
176 if (ret)
177 return -EFAULT;
178
179 switch (owner.type) {
180 case F_OWNER_TID:
181 type = PIDTYPE_PID;
182 break;
183
184 case F_OWNER_PID:
185 type = PIDTYPE_TGID;
186 break;
187
188 case F_OWNER_PGRP:
189 type = PIDTYPE_PGID;
190 break;
191
192 default:
193 return -EINVAL;
194 }
195
196 rcu_read_lock();
197 pid = find_vpid(nr: owner.pid);
198 if (owner.pid && !pid)
199 ret = -ESRCH;
200 else
201 __f_setown(filp, pid, type, 1);
202 rcu_read_unlock();
203
204 return ret;
205}
206
207static int f_getown_ex(struct file *filp, unsigned long arg)
208{
209 struct f_owner_ex __user *owner_p = (void __user *)arg;
210 struct f_owner_ex owner = {};
211 int ret = 0;
212
213 read_lock_irq(&filp->f_owner.lock);
214 rcu_read_lock();
215 if (pid_task(pid: filp->f_owner.pid, filp->f_owner.pid_type))
216 owner.pid = pid_vnr(pid: filp->f_owner.pid);
217 rcu_read_unlock();
218 switch (filp->f_owner.pid_type) {
219 case PIDTYPE_PID:
220 owner.type = F_OWNER_TID;
221 break;
222
223 case PIDTYPE_TGID:
224 owner.type = F_OWNER_PID;
225 break;
226
227 case PIDTYPE_PGID:
228 owner.type = F_OWNER_PGRP;
229 break;
230
231 default:
232 WARN_ON(1);
233 ret = -EINVAL;
234 break;
235 }
236 read_unlock_irq(&filp->f_owner.lock);
237
238 if (!ret) {
239 ret = copy_to_user(to: owner_p, from: &owner, n: sizeof(owner));
240 if (ret)
241 ret = -EFAULT;
242 }
243 return ret;
244}
245
246#ifdef CONFIG_CHECKPOINT_RESTORE
247static int f_getowner_uids(struct file *filp, unsigned long arg)
248{
249 struct user_namespace *user_ns = current_user_ns();
250 uid_t __user *dst = (void __user *)arg;
251 uid_t src[2];
252 int err;
253
254 read_lock_irq(&filp->f_owner.lock);
255 src[0] = from_kuid(to: user_ns, uid: filp->f_owner.uid);
256 src[1] = from_kuid(to: user_ns, uid: filp->f_owner.euid);
257 read_unlock_irq(&filp->f_owner.lock);
258
259 err = put_user(src[0], &dst[0]);
260 err |= put_user(src[1], &dst[1]);
261
262 return err;
263}
264#else
265static int f_getowner_uids(struct file *filp, unsigned long arg)
266{
267 return -EINVAL;
268}
269#endif
270
271static bool rw_hint_valid(enum rw_hint hint)
272{
273 switch (hint) {
274 case RWH_WRITE_LIFE_NOT_SET:
275 case RWH_WRITE_LIFE_NONE:
276 case RWH_WRITE_LIFE_SHORT:
277 case RWH_WRITE_LIFE_MEDIUM:
278 case RWH_WRITE_LIFE_LONG:
279 case RWH_WRITE_LIFE_EXTREME:
280 return true;
281 default:
282 return false;
283 }
284}
285
286static long fcntl_rw_hint(struct file *file, unsigned int cmd,
287 unsigned long arg)
288{
289 struct inode *inode = file_inode(f: file);
290 u64 __user *argp = (u64 __user *)arg;
291 enum rw_hint hint;
292 u64 h;
293
294 switch (cmd) {
295 case F_GET_RW_HINT:
296 h = inode->i_write_hint;
297 if (copy_to_user(to: argp, from: &h, n: sizeof(*argp)))
298 return -EFAULT;
299 return 0;
300 case F_SET_RW_HINT:
301 if (copy_from_user(to: &h, from: argp, n: sizeof(h)))
302 return -EFAULT;
303 hint = (enum rw_hint) h;
304 if (!rw_hint_valid(hint))
305 return -EINVAL;
306
307 inode_lock(inode);
308 inode->i_write_hint = hint;
309 inode_unlock(inode);
310 return 0;
311 default:
312 return -EINVAL;
313 }
314}
315
316static long do_fcntl(int fd, unsigned int cmd, unsigned long arg,
317 struct file *filp)
318{
319 void __user *argp = (void __user *)arg;
320 int argi = (int)arg;
321 struct flock flock;
322 long err = -EINVAL;
323
324 switch (cmd) {
325 case F_DUPFD:
326 err = f_dupfd(from: argi, file: filp, flags: 0);
327 break;
328 case F_DUPFD_CLOEXEC:
329 err = f_dupfd(from: argi, file: filp, O_CLOEXEC);
330 break;
331 case F_GETFD:
332 err = get_close_on_exec(fd) ? FD_CLOEXEC : 0;
333 break;
334 case F_SETFD:
335 err = 0;
336 set_close_on_exec(fd, flag: argi & FD_CLOEXEC);
337 break;
338 case F_GETFL:
339 err = filp->f_flags;
340 break;
341 case F_SETFL:
342 err = setfl(fd, filp, arg: argi);
343 break;
344#if BITS_PER_LONG != 32
345 /* 32-bit arches must use fcntl64() */
346 case F_OFD_GETLK:
347#endif
348 case F_GETLK:
349 if (copy_from_user(to: &flock, from: argp, n: sizeof(flock)))
350 return -EFAULT;
351 err = fcntl_getlk(filp, cmd, &flock);
352 if (!err && copy_to_user(to: argp, from: &flock, n: sizeof(flock)))
353 return -EFAULT;
354 break;
355#if BITS_PER_LONG != 32
356 /* 32-bit arches must use fcntl64() */
357 case F_OFD_SETLK:
358 case F_OFD_SETLKW:
359 fallthrough;
360#endif
361 case F_SETLK:
362 case F_SETLKW:
363 if (copy_from_user(to: &flock, from: argp, n: sizeof(flock)))
364 return -EFAULT;
365 err = fcntl_setlk(fd, filp, cmd, &flock);
366 break;
367 case F_GETOWN:
368 /*
369 * XXX If f_owner is a process group, the
370 * negative return value will get converted
371 * into an error. Oops. If we keep the
372 * current syscall conventions, the only way
373 * to fix this will be in libc.
374 */
375 err = f_getown(filp);
376 force_successful_syscall_return();
377 break;
378 case F_SETOWN:
379 err = f_setown(filp, argi, 1);
380 break;
381 case F_GETOWN_EX:
382 err = f_getown_ex(filp, arg);
383 break;
384 case F_SETOWN_EX:
385 err = f_setown_ex(filp, arg);
386 break;
387 case F_GETOWNER_UIDS:
388 err = f_getowner_uids(filp, arg);
389 break;
390 case F_GETSIG:
391 err = filp->f_owner.signum;
392 break;
393 case F_SETSIG:
394 /* arg == 0 restores default behaviour. */
395 if (!valid_signal(sig: argi)) {
396 break;
397 }
398 err = 0;
399 filp->f_owner.signum = argi;
400 break;
401 case F_GETLEASE:
402 err = fcntl_getlease(filp);
403 break;
404 case F_SETLEASE:
405 err = fcntl_setlease(fd, filp, arg: argi);
406 break;
407 case F_NOTIFY:
408 err = fcntl_dirnotify(fd, filp, argi);
409 break;
410 case F_SETPIPE_SZ:
411 case F_GETPIPE_SZ:
412 err = pipe_fcntl(filp, cmd, arg: argi);
413 break;
414 case F_ADD_SEALS:
415 case F_GET_SEALS:
416 err = memfd_fcntl(file: filp, cmd, arg: argi);
417 break;
418 case F_GET_RW_HINT:
419 case F_SET_RW_HINT:
420 err = fcntl_rw_hint(file: filp, cmd, arg);
421 break;
422 default:
423 break;
424 }
425 return err;
426}
427
428static int check_fcntl_cmd(unsigned cmd)
429{
430 switch (cmd) {
431 case F_DUPFD:
432 case F_DUPFD_CLOEXEC:
433 case F_GETFD:
434 case F_SETFD:
435 case F_GETFL:
436 return 1;
437 }
438 return 0;
439}
440
441SYSCALL_DEFINE3(fcntl, unsigned int, fd, unsigned int, cmd, unsigned long, arg)
442{
443 struct fd f = fdget_raw(fd);
444 long err = -EBADF;
445
446 if (!f.file)
447 goto out;
448
449 if (unlikely(f.file->f_mode & FMODE_PATH)) {
450 if (!check_fcntl_cmd(cmd))
451 goto out1;
452 }
453
454 err = security_file_fcntl(file: f.file, cmd, arg);
455 if (!err)
456 err = do_fcntl(fd, cmd, arg, filp: f.file);
457
458out1:
459 fdput(fd: f);
460out:
461 return err;
462}
463
464#if BITS_PER_LONG == 32
465SYSCALL_DEFINE3(fcntl64, unsigned int, fd, unsigned int, cmd,
466 unsigned long, arg)
467{
468 void __user *argp = (void __user *)arg;
469 struct fd f = fdget_raw(fd);
470 struct flock64 flock;
471 long err = -EBADF;
472
473 if (!f.file)
474 goto out;
475
476 if (unlikely(f.file->f_mode & FMODE_PATH)) {
477 if (!check_fcntl_cmd(cmd))
478 goto out1;
479 }
480
481 err = security_file_fcntl(f.file, cmd, arg);
482 if (err)
483 goto out1;
484
485 switch (cmd) {
486 case F_GETLK64:
487 case F_OFD_GETLK:
488 err = -EFAULT;
489 if (copy_from_user(&flock, argp, sizeof(flock)))
490 break;
491 err = fcntl_getlk64(f.file, cmd, &flock);
492 if (!err && copy_to_user(argp, &flock, sizeof(flock)))
493 err = -EFAULT;
494 break;
495 case F_SETLK64:
496 case F_SETLKW64:
497 case F_OFD_SETLK:
498 case F_OFD_SETLKW:
499 err = -EFAULT;
500 if (copy_from_user(&flock, argp, sizeof(flock)))
501 break;
502 err = fcntl_setlk64(fd, f.file, cmd, &flock);
503 break;
504 default:
505 err = do_fcntl(fd, cmd, arg, f.file);
506 break;
507 }
508out1:
509 fdput(f);
510out:
511 return err;
512}
513#endif
514
515#ifdef CONFIG_COMPAT
516/* careful - don't use anywhere else */
517#define copy_flock_fields(dst, src) \
518 (dst)->l_type = (src)->l_type; \
519 (dst)->l_whence = (src)->l_whence; \
520 (dst)->l_start = (src)->l_start; \
521 (dst)->l_len = (src)->l_len; \
522 (dst)->l_pid = (src)->l_pid;
523
524static int get_compat_flock(struct flock *kfl, const struct compat_flock __user *ufl)
525{
526 struct compat_flock fl;
527
528 if (copy_from_user(to: &fl, from: ufl, n: sizeof(struct compat_flock)))
529 return -EFAULT;
530 copy_flock_fields(kfl, &fl);
531 return 0;
532}
533
534static int get_compat_flock64(struct flock *kfl, const struct compat_flock64 __user *ufl)
535{
536 struct compat_flock64 fl;
537
538 if (copy_from_user(to: &fl, from: ufl, n: sizeof(struct compat_flock64)))
539 return -EFAULT;
540 copy_flock_fields(kfl, &fl);
541 return 0;
542}
543
544static int put_compat_flock(const struct flock *kfl, struct compat_flock __user *ufl)
545{
546 struct compat_flock fl;
547
548 memset(&fl, 0, sizeof(struct compat_flock));
549 copy_flock_fields(&fl, kfl);
550 if (copy_to_user(to: ufl, from: &fl, n: sizeof(struct compat_flock)))
551 return -EFAULT;
552 return 0;
553}
554
555static int put_compat_flock64(const struct flock *kfl, struct compat_flock64 __user *ufl)
556{
557 struct compat_flock64 fl;
558
559 BUILD_BUG_ON(sizeof(kfl->l_start) > sizeof(ufl->l_start));
560 BUILD_BUG_ON(sizeof(kfl->l_len) > sizeof(ufl->l_len));
561
562 memset(&fl, 0, sizeof(struct compat_flock64));
563 copy_flock_fields(&fl, kfl);
564 if (copy_to_user(to: ufl, from: &fl, n: sizeof(struct compat_flock64)))
565 return -EFAULT;
566 return 0;
567}
568#undef copy_flock_fields
569
570static unsigned int
571convert_fcntl_cmd(unsigned int cmd)
572{
573 switch (cmd) {
574 case F_GETLK64:
575 return F_GETLK;
576 case F_SETLK64:
577 return F_SETLK;
578 case F_SETLKW64:
579 return F_SETLKW;
580 }
581
582 return cmd;
583}
584
585/*
586 * GETLK was successful and we need to return the data, but it needs to fit in
587 * the compat structure.
588 * l_start shouldn't be too big, unless the original start + end is greater than
589 * COMPAT_OFF_T_MAX, in which case the app was asking for trouble, so we return
590 * -EOVERFLOW in that case. l_len could be too big, in which case we just
591 * truncate it, and only allow the app to see that part of the conflicting lock
592 * that might make sense to it anyway
593 */
594static int fixup_compat_flock(struct flock *flock)
595{
596 if (flock->l_start > COMPAT_OFF_T_MAX)
597 return -EOVERFLOW;
598 if (flock->l_len > COMPAT_OFF_T_MAX)
599 flock->l_len = COMPAT_OFF_T_MAX;
600 return 0;
601}
602
603static long do_compat_fcntl64(unsigned int fd, unsigned int cmd,
604 compat_ulong_t arg)
605{
606 struct fd f = fdget_raw(fd);
607 struct flock flock;
608 long err = -EBADF;
609
610 if (!f.file)
611 return err;
612
613 if (unlikely(f.file->f_mode & FMODE_PATH)) {
614 if (!check_fcntl_cmd(cmd))
615 goto out_put;
616 }
617
618 err = security_file_fcntl(file: f.file, cmd, arg);
619 if (err)
620 goto out_put;
621
622 switch (cmd) {
623 case F_GETLK:
624 err = get_compat_flock(kfl: &flock, ufl: compat_ptr(uptr: arg));
625 if (err)
626 break;
627 err = fcntl_getlk(f.file, convert_fcntl_cmd(cmd), &flock);
628 if (err)
629 break;
630 err = fixup_compat_flock(flock: &flock);
631 if (!err)
632 err = put_compat_flock(kfl: &flock, ufl: compat_ptr(uptr: arg));
633 break;
634 case F_GETLK64:
635 case F_OFD_GETLK:
636 err = get_compat_flock64(kfl: &flock, ufl: compat_ptr(uptr: arg));
637 if (err)
638 break;
639 err = fcntl_getlk(f.file, convert_fcntl_cmd(cmd), &flock);
640 if (!err)
641 err = put_compat_flock64(kfl: &flock, ufl: compat_ptr(uptr: arg));
642 break;
643 case F_SETLK:
644 case F_SETLKW:
645 err = get_compat_flock(kfl: &flock, ufl: compat_ptr(uptr: arg));
646 if (err)
647 break;
648 err = fcntl_setlk(fd, f.file, convert_fcntl_cmd(cmd), &flock);
649 break;
650 case F_SETLK64:
651 case F_SETLKW64:
652 case F_OFD_SETLK:
653 case F_OFD_SETLKW:
654 err = get_compat_flock64(kfl: &flock, ufl: compat_ptr(uptr: arg));
655 if (err)
656 break;
657 err = fcntl_setlk(fd, f.file, convert_fcntl_cmd(cmd), &flock);
658 break;
659 default:
660 err = do_fcntl(fd, cmd, arg, filp: f.file);
661 break;
662 }
663out_put:
664 fdput(fd: f);
665 return err;
666}
667
668COMPAT_SYSCALL_DEFINE3(fcntl64, unsigned int, fd, unsigned int, cmd,
669 compat_ulong_t, arg)
670{
671 return do_compat_fcntl64(fd, cmd, arg);
672}
673
674COMPAT_SYSCALL_DEFINE3(fcntl, unsigned int, fd, unsigned int, cmd,
675 compat_ulong_t, arg)
676{
677 switch (cmd) {
678 case F_GETLK64:
679 case F_SETLK64:
680 case F_SETLKW64:
681 case F_OFD_GETLK:
682 case F_OFD_SETLK:
683 case F_OFD_SETLKW:
684 return -EINVAL;
685 }
686 return do_compat_fcntl64(fd, cmd, arg);
687}
688#endif
689
690/* Table to convert sigio signal codes into poll band bitmaps */
691
692static const __poll_t band_table[NSIGPOLL] = {
693 EPOLLIN | EPOLLRDNORM, /* POLL_IN */
694 EPOLLOUT | EPOLLWRNORM | EPOLLWRBAND, /* POLL_OUT */
695 EPOLLIN | EPOLLRDNORM | EPOLLMSG, /* POLL_MSG */
696 EPOLLERR, /* POLL_ERR */
697 EPOLLPRI | EPOLLRDBAND, /* POLL_PRI */
698 EPOLLHUP | EPOLLERR /* POLL_HUP */
699};
700
701static inline int sigio_perm(struct task_struct *p,
702 struct fown_struct *fown, int sig)
703{
704 const struct cred *cred;
705 int ret;
706
707 rcu_read_lock();
708 cred = __task_cred(p);
709 ret = ((uid_eq(left: fown->euid, GLOBAL_ROOT_UID) ||
710 uid_eq(fown->euid, cred->suid) || uid_eq(fown->euid, cred->uid) ||
711 uid_eq(fown->uid, cred->suid) || uid_eq(fown->uid, cred->uid)) &&
712 !security_file_send_sigiotask(p, fown, sig));
713 rcu_read_unlock();
714 return ret;
715}
716
717static void send_sigio_to_task(struct task_struct *p,
718 struct fown_struct *fown,
719 int fd, int reason, enum pid_type type)
720{
721 /*
722 * F_SETSIG can change ->signum lockless in parallel, make
723 * sure we read it once and use the same value throughout.
724 */
725 int signum = READ_ONCE(fown->signum);
726
727 if (!sigio_perm(p, fown, sig: signum))
728 return;
729
730 switch (signum) {
731 default: {
732 kernel_siginfo_t si;
733
734 /* Queue a rt signal with the appropriate fd as its
735 value. We use SI_SIGIO as the source, not
736 SI_KERNEL, since kernel signals always get
737 delivered even if we can't queue. Failure to
738 queue in this case _should_ be reported; we fall
739 back to SIGIO in that case. --sct */
740 clear_siginfo(info: &si);
741 si.si_signo = signum;
742 si.si_errno = 0;
743 si.si_code = reason;
744 /*
745 * Posix definies POLL_IN and friends to be signal
746 * specific si_codes for SIG_POLL. Linux extended
747 * these si_codes to other signals in a way that is
748 * ambiguous if other signals also have signal
749 * specific si_codes. In that case use SI_SIGIO instead
750 * to remove the ambiguity.
751 */
752 if ((signum != SIGPOLL) && sig_specific_sicodes(signum))
753 si.si_code = SI_SIGIO;
754
755 /* Make sure we are called with one of the POLL_*
756 reasons, otherwise we could leak kernel stack into
757 userspace. */
758 BUG_ON((reason < POLL_IN) || ((reason - POLL_IN) >= NSIGPOLL));
759 if (reason - POLL_IN >= NSIGPOLL)
760 si.si_band = ~0L;
761 else
762 si.si_band = mangle_poll(val: band_table[reason - POLL_IN]);
763 si.si_fd = fd;
764 if (!do_send_sig_info(sig: signum, info: &si, p, type))
765 break;
766 }
767 fallthrough; /* fall back on the old plain SIGIO signal */
768 case 0:
769 do_send_sig_info(SIGIO, SEND_SIG_PRIV, p, type);
770 }
771}
772
773void send_sigio(struct fown_struct *fown, int fd, int band)
774{
775 struct task_struct *p;
776 enum pid_type type;
777 unsigned long flags;
778 struct pid *pid;
779
780 read_lock_irqsave(&fown->lock, flags);
781
782 type = fown->pid_type;
783 pid = fown->pid;
784 if (!pid)
785 goto out_unlock_fown;
786
787 if (type <= PIDTYPE_TGID) {
788 rcu_read_lock();
789 p = pid_task(pid, PIDTYPE_PID);
790 if (p)
791 send_sigio_to_task(p, fown, fd, reason: band, type);
792 rcu_read_unlock();
793 } else {
794 read_lock(&tasklist_lock);
795 do_each_pid_task(pid, type, p) {
796 send_sigio_to_task(p, fown, fd, reason: band, type);
797 } while_each_pid_task(pid, type, p);
798 read_unlock(&tasklist_lock);
799 }
800 out_unlock_fown:
801 read_unlock_irqrestore(&fown->lock, flags);
802}
803
804static void send_sigurg_to_task(struct task_struct *p,
805 struct fown_struct *fown, enum pid_type type)
806{
807 if (sigio_perm(p, fown, SIGURG))
808 do_send_sig_info(SIGURG, SEND_SIG_PRIV, p, type);
809}
810
811int send_sigurg(struct fown_struct *fown)
812{
813 struct task_struct *p;
814 enum pid_type type;
815 struct pid *pid;
816 unsigned long flags;
817 int ret = 0;
818
819 read_lock_irqsave(&fown->lock, flags);
820
821 type = fown->pid_type;
822 pid = fown->pid;
823 if (!pid)
824 goto out_unlock_fown;
825
826 ret = 1;
827
828 if (type <= PIDTYPE_TGID) {
829 rcu_read_lock();
830 p = pid_task(pid, PIDTYPE_PID);
831 if (p)
832 send_sigurg_to_task(p, fown, type);
833 rcu_read_unlock();
834 } else {
835 read_lock(&tasklist_lock);
836 do_each_pid_task(pid, type, p) {
837 send_sigurg_to_task(p, fown, type);
838 } while_each_pid_task(pid, type, p);
839 read_unlock(&tasklist_lock);
840 }
841 out_unlock_fown:
842 read_unlock_irqrestore(&fown->lock, flags);
843 return ret;
844}
845
846static DEFINE_SPINLOCK(fasync_lock);
847static struct kmem_cache *fasync_cache __ro_after_init;
848
849static void fasync_free_rcu(struct rcu_head *head)
850{
851 kmem_cache_free(s: fasync_cache,
852 container_of(head, struct fasync_struct, fa_rcu));
853}
854
855/*
856 * Remove a fasync entry. If successfully removed, return
857 * positive and clear the FASYNC flag. If no entry exists,
858 * do nothing and return 0.
859 *
860 * NOTE! It is very important that the FASYNC flag always
861 * match the state "is the filp on a fasync list".
862 *
863 */
864int fasync_remove_entry(struct file *filp, struct fasync_struct **fapp)
865{
866 struct fasync_struct *fa, **fp;
867 int result = 0;
868
869 spin_lock(lock: &filp->f_lock);
870 spin_lock(lock: &fasync_lock);
871 for (fp = fapp; (fa = *fp) != NULL; fp = &fa->fa_next) {
872 if (fa->fa_file != filp)
873 continue;
874
875 write_lock_irq(&fa->fa_lock);
876 fa->fa_file = NULL;
877 write_unlock_irq(&fa->fa_lock);
878
879 *fp = fa->fa_next;
880 call_rcu(head: &fa->fa_rcu, func: fasync_free_rcu);
881 filp->f_flags &= ~FASYNC;
882 result = 1;
883 break;
884 }
885 spin_unlock(lock: &fasync_lock);
886 spin_unlock(lock: &filp->f_lock);
887 return result;
888}
889
890struct fasync_struct *fasync_alloc(void)
891{
892 return kmem_cache_alloc(cachep: fasync_cache, GFP_KERNEL);
893}
894
895/*
896 * NOTE! This can be used only for unused fasync entries:
897 * entries that actually got inserted on the fasync list
898 * need to be released by rcu - see fasync_remove_entry.
899 */
900void fasync_free(struct fasync_struct *new)
901{
902 kmem_cache_free(s: fasync_cache, objp: new);
903}
904
905/*
906 * Insert a new entry into the fasync list. Return the pointer to the
907 * old one if we didn't use the new one.
908 *
909 * NOTE! It is very important that the FASYNC flag always
910 * match the state "is the filp on a fasync list".
911 */
912struct fasync_struct *fasync_insert_entry(int fd, struct file *filp, struct fasync_struct **fapp, struct fasync_struct *new)
913{
914 struct fasync_struct *fa, **fp;
915
916 spin_lock(lock: &filp->f_lock);
917 spin_lock(lock: &fasync_lock);
918 for (fp = fapp; (fa = *fp) != NULL; fp = &fa->fa_next) {
919 if (fa->fa_file != filp)
920 continue;
921
922 write_lock_irq(&fa->fa_lock);
923 fa->fa_fd = fd;
924 write_unlock_irq(&fa->fa_lock);
925 goto out;
926 }
927
928 rwlock_init(&new->fa_lock);
929 new->magic = FASYNC_MAGIC;
930 new->fa_file = filp;
931 new->fa_fd = fd;
932 new->fa_next = *fapp;
933 rcu_assign_pointer(*fapp, new);
934 filp->f_flags |= FASYNC;
935
936out:
937 spin_unlock(lock: &fasync_lock);
938 spin_unlock(lock: &filp->f_lock);
939 return fa;
940}
941
942/*
943 * Add a fasync entry. Return negative on error, positive if
944 * added, and zero if did nothing but change an existing one.
945 */
946static int fasync_add_entry(int fd, struct file *filp, struct fasync_struct **fapp)
947{
948 struct fasync_struct *new;
949
950 new = fasync_alloc();
951 if (!new)
952 return -ENOMEM;
953
954 /*
955 * fasync_insert_entry() returns the old (update) entry if
956 * it existed.
957 *
958 * So free the (unused) new entry and return 0 to let the
959 * caller know that we didn't add any new fasync entries.
960 */
961 if (fasync_insert_entry(fd, filp, fapp, new)) {
962 fasync_free(new);
963 return 0;
964 }
965
966 return 1;
967}
968
969/*
970 * fasync_helper() is used by almost all character device drivers
971 * to set up the fasync queue, and for regular files by the file
972 * lease code. It returns negative on error, 0 if it did no changes
973 * and positive if it added/deleted the entry.
974 */
975int fasync_helper(int fd, struct file * filp, int on, struct fasync_struct **fapp)
976{
977 if (!on)
978 return fasync_remove_entry(filp, fapp);
979 return fasync_add_entry(fd, filp, fapp);
980}
981
982EXPORT_SYMBOL(fasync_helper);
983
984/*
985 * rcu_read_lock() is held
986 */
987static void kill_fasync_rcu(struct fasync_struct *fa, int sig, int band)
988{
989 while (fa) {
990 struct fown_struct *fown;
991 unsigned long flags;
992
993 if (fa->magic != FASYNC_MAGIC) {
994 printk(KERN_ERR "kill_fasync: bad magic number in "
995 "fasync_struct!\n");
996 return;
997 }
998 read_lock_irqsave(&fa->fa_lock, flags);
999 if (fa->fa_file) {
1000 fown = &fa->fa_file->f_owner;
1001 /* Don't send SIGURG to processes which have not set a
1002 queued signum: SIGURG has its own default signalling
1003 mechanism. */
1004 if (!(sig == SIGURG && fown->signum == 0))
1005 send_sigio(fown, fd: fa->fa_fd, band);
1006 }
1007 read_unlock_irqrestore(&fa->fa_lock, flags);
1008 fa = rcu_dereference(fa->fa_next);
1009 }
1010}
1011
1012void kill_fasync(struct fasync_struct **fp, int sig, int band)
1013{
1014 /* First a quick test without locking: usually
1015 * the list is empty.
1016 */
1017 if (*fp) {
1018 rcu_read_lock();
1019 kill_fasync_rcu(rcu_dereference(*fp), sig, band);
1020 rcu_read_unlock();
1021 }
1022}
1023EXPORT_SYMBOL(kill_fasync);
1024
1025static int __init fcntl_init(void)
1026{
1027 /*
1028 * Please add new bits here to ensure allocation uniqueness.
1029 * Exceptions: O_NONBLOCK is a two bit define on parisc; O_NDELAY
1030 * is defined as O_NONBLOCK on some platforms and not on others.
1031 */
1032 BUILD_BUG_ON(21 - 1 /* for O_RDONLY being 0 */ !=
1033 HWEIGHT32(
1034 (VALID_OPEN_FLAGS & ~(O_NONBLOCK | O_NDELAY)) |
1035 __FMODE_EXEC | __FMODE_NONOTIFY));
1036
1037 fasync_cache = kmem_cache_create(name: "fasync_cache",
1038 size: sizeof(struct fasync_struct), align: 0,
1039 SLAB_PANIC | SLAB_ACCOUNT, NULL);
1040 return 0;
1041}
1042
1043module_init(fcntl_init)
1044

source code of linux/fs/fcntl.c