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TOMOYO Linux Cross Reference
Linux/fs/fcntl.c

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

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