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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/capability.h>
13 #include <linux/dnotify.h>
14 #include <linux/smp_lock.h>
15 #include <linux/slab.h>
16 #include <linux/module.h>
17 #include <linux/security.h>
18 #include <linux/ptrace.h>
19 #include <linux/signal.h>
20 #include <linux/rcupdate.h>
21 #include <linux/pid_namespace.h>
22
23 #include <asm/poll.h>
24 #include <asm/siginfo.h>
25 #include <asm/uaccess.h>
26
27 void set_close_on_exec(unsigned int fd, int flag)
28 {
29 struct files_struct *files = current->files;
30 struct fdtable *fdt;
31 spin_lock(&files->file_lock);
32 fdt = files_fdtable(files);
33 if (flag)
34 FD_SET(fd, fdt->close_on_exec);
35 else
36 FD_CLR(fd, fdt->close_on_exec);
37 spin_unlock(&files->file_lock);
38 }
39
40 static int get_close_on_exec(unsigned int fd)
41 {
42 struct files_struct *files = current->files;
43 struct fdtable *fdt;
44 int res;
45 rcu_read_lock();
46 fdt = files_fdtable(files);
47 res = FD_ISSET(fd, fdt->close_on_exec);
48 rcu_read_unlock();
49 return res;
50 }
51
52 /*
53 * locate_fd finds a free file descriptor in the open_fds fdset,
54 * expanding the fd arrays if necessary. Must be called with the
55 * file_lock held for write.
56 */
57
58 static int locate_fd(unsigned int orig_start, int cloexec)
59 {
60 struct files_struct *files = current->files;
61 unsigned int newfd;
62 unsigned int start;
63 int error;
64 struct fdtable *fdt;
65
66 spin_lock(&files->file_lock);
67
68 error = -EINVAL;
69 if (orig_start >= current->signal->rlim[RLIMIT_NOFILE].rlim_cur)
70 goto out;
71
72 repeat:
73 fdt = files_fdtable(files);
74 /*
75 * Someone might have closed fd's in the range
76 * orig_start..fdt->next_fd
77 */
78 start = orig_start;
79 if (start < files->next_fd)
80 start = files->next_fd;
81
82 newfd = start;
83 if (start < fdt->max_fds)
84 newfd = find_next_zero_bit(fdt->open_fds->fds_bits,
85 fdt->max_fds, start);
86
87 error = -EMFILE;
88 if (newfd >= current->signal->rlim[RLIMIT_NOFILE].rlim_cur)
89 goto out;
90
91 error = expand_files(files, newfd);
92 if (error < 0)
93 goto out;
94
95 /*
96 * If we needed to expand the fs array we
97 * might have blocked - try again.
98 */
99 if (error)
100 goto repeat;
101
102 if (start <= files->next_fd)
103 files->next_fd = newfd + 1;
104
105 FD_SET(newfd, fdt->open_fds);
106 if (cloexec)
107 FD_SET(newfd, fdt->close_on_exec);
108 else
109 FD_CLR(newfd, fdt->close_on_exec);
110 error = newfd;
111
112 out:
113 spin_unlock(&files->file_lock);
114 return error;
115 }
116
117 static int dupfd(struct file *file, unsigned int start, int cloexec)
118 {
119 int fd = locate_fd(start, cloexec);
120 if (fd >= 0)
121 fd_install(fd, file);
122 else
123 fput(file);
124
125 return fd;
126 }
127
128 asmlinkage long sys_dup2(unsigned int oldfd, unsigned int newfd)
129 {
130 int err = -EBADF;
131 struct file * file, *tofree;
132 struct files_struct * files = current->files;
133 struct fdtable *fdt;
134
135 spin_lock(&files->file_lock);
136 if (!(file = fcheck(oldfd)))
137 goto out_unlock;
138 err = newfd;
139 if (newfd == oldfd)
140 goto out_unlock;
141 err = -EBADF;
142 if (newfd >= current->signal->rlim[RLIMIT_NOFILE].rlim_cur)
143 goto out_unlock;
144 get_file(file); /* We are now finished with oldfd */
145
146 err = expand_files(files, newfd);
147 if (err < 0)
148 goto out_fput;
149
150 /* To avoid races with open() and dup(), we will mark the fd as
151 * in-use in the open-file bitmap throughout the entire dup2()
152 * process. This is quite safe: do_close() uses the fd array
153 * entry, not the bitmap, to decide what work needs to be
154 * done. --sct */
155 /* Doesn't work. open() might be there first. --AV */
156
157 /* Yes. It's a race. In user space. Nothing sane to do */
158 err = -EBUSY;
159 fdt = files_fdtable(files);
160 tofree = fdt->fd[newfd];
161 if (!tofree && FD_ISSET(newfd, fdt->open_fds))
162 goto out_fput;
163
164 rcu_assign_pointer(fdt->fd[newfd], file);
165 FD_SET(newfd, fdt->open_fds);
166 FD_CLR(newfd, fdt->close_on_exec);
167 spin_unlock(&files->file_lock);
168
169 if (tofree)
170 filp_close(tofree, files);
171 err = newfd;
172 out:
173 return err;
174 out_unlock:
175 spin_unlock(&files->file_lock);
176 goto out;
177
178 out_fput:
179 spin_unlock(&files->file_lock);
180 fput(file);
181 goto out;
182 }
183
184 asmlinkage long sys_dup(unsigned int fildes)
185 {
186 int ret = -EBADF;
187 struct file * file = fget(fildes);
188
189 if (file)
190 ret = dupfd(file, 0, 0);
191 return ret;
192 }
193
194 #define SETFL_MASK (O_APPEND | O_NONBLOCK | O_NDELAY | FASYNC | O_DIRECT | O_NOATIME)
195
196 static int setfl(int fd, struct file * filp, unsigned long arg)
197 {
198 struct inode * inode = filp->f_path.dentry->d_inode;
199 int error = 0;
200
201 /*
202 * O_APPEND cannot be cleared if the file is marked as append-only
203 * and the file is open for write.
204 */
205 if (((arg ^ filp->f_flags) & O_APPEND) && IS_APPEND(inode))
206 return -EPERM;
207
208 /* O_NOATIME can only be set by the owner or superuser */
209 if ((arg & O_NOATIME) && !(filp->f_flags & O_NOATIME))
210 if (!is_owner_or_cap(inode))
211 return -EPERM;
212
213 /* required for strict SunOS emulation */
214 if (O_NONBLOCK != O_NDELAY)
215 if (arg & O_NDELAY)
216 arg |= O_NONBLOCK;
217
218 if (arg & O_DIRECT) {
219 if (!filp->f_mapping || !filp->f_mapping->a_ops ||
220 !filp->f_mapping->a_ops->direct_IO)
221 return -EINVAL;
222 }
223
224 if (filp->f_op && filp->f_op->check_flags)
225 error = filp->f_op->check_flags(arg);
226 if (error)
227 return error;
228
229 lock_kernel();
230 if ((arg ^ filp->f_flags) & FASYNC) {
231 if (filp->f_op && filp->f_op->fasync) {
232 error = filp->f_op->fasync(fd, filp, (arg & FASYNC) != 0);
233 if (error < 0)
234 goto out;
235 }
236 }
237
238 filp->f_flags = (arg & SETFL_MASK) | (filp->f_flags & ~SETFL_MASK);
239 out:
240 unlock_kernel();
241 return error;
242 }
243
244 static void f_modown(struct file *filp, struct pid *pid, enum pid_type type,
245 uid_t uid, uid_t euid, int force)
246 {
247 write_lock_irq(&filp->f_owner.lock);
248 if (force || !filp->f_owner.pid) {
249 put_pid(filp->f_owner.pid);
250 filp->f_owner.pid = get_pid(pid);
251 filp->f_owner.pid_type = type;
252 filp->f_owner.uid = uid;
253 filp->f_owner.euid = euid;
254 }
255 write_unlock_irq(&filp->f_owner.lock);
256 }
257
258 int __f_setown(struct file *filp, struct pid *pid, enum pid_type type,
259 int force)
260 {
261 int err;
262
263 err = security_file_set_fowner(filp);
264 if (err)
265 return err;
266
267 f_modown(filp, pid, type, current->uid, current->euid, force);
268 return 0;
269 }
270 EXPORT_SYMBOL(__f_setown);
271
272 int f_setown(struct file *filp, unsigned long arg, int force)
273 {
274 enum pid_type type;
275 struct pid *pid;
276 int who = arg;
277 int result;
278 type = PIDTYPE_PID;
279 if (who < 0) {
280 type = PIDTYPE_PGID;
281 who = -who;
282 }
283 rcu_read_lock();
284 pid = find_vpid(who);
285 result = __f_setown(filp, pid, type, force);
286 rcu_read_unlock();
287 return result;
288 }
289 EXPORT_SYMBOL(f_setown);
290
291 void f_delown(struct file *filp)
292 {
293 f_modown(filp, NULL, PIDTYPE_PID, 0, 0, 1);
294 }
295
296 pid_t f_getown(struct file *filp)
297 {
298 pid_t pid;
299 read_lock(&filp->f_owner.lock);
300 pid = pid_vnr(filp->f_owner.pid);
301 if (filp->f_owner.pid_type == PIDTYPE_PGID)
302 pid = -pid;
303 read_unlock(&filp->f_owner.lock);
304 return pid;
305 }
306
307 static long do_fcntl(int fd, unsigned int cmd, unsigned long arg,
308 struct file *filp)
309 {
310 long err = -EINVAL;
311
312 switch (cmd) {
313 case F_DUPFD:
314 case F_DUPFD_CLOEXEC:
315 get_file(filp);
316 err = dupfd(filp, arg, cmd == F_DUPFD_CLOEXEC);
317 break;
318 case F_GETFD:
319 err = get_close_on_exec(fd) ? FD_CLOEXEC : 0;
320 break;
321 case F_SETFD:
322 err = 0;
323 set_close_on_exec(fd, arg & FD_CLOEXEC);
324 break;
325 case F_GETFL:
326 err = filp->f_flags;
327 break;
328 case F_SETFL:
329 err = setfl(fd, filp, arg);
330 break;
331 case F_GETLK:
332 err = fcntl_getlk(filp, (struct flock __user *) arg);
333 break;
334 case F_SETLK:
335 case F_SETLKW:
336 err = fcntl_setlk(fd, filp, cmd, (struct flock __user *) arg);
337 break;
338 case F_GETOWN:
339 /*
340 * XXX If f_owner is a process group, the
341 * negative return value will get converted
342 * into an error. Oops. If we keep the
343 * current syscall conventions, the only way
344 * to fix this will be in libc.
345 */
346 err = f_getown(filp);
347 force_successful_syscall_return();
348 break;
349 case F_SETOWN:
350 err = f_setown(filp, arg, 1);
351 break;
352 case F_GETSIG:
353 err = filp->f_owner.signum;
354 break;
355 case F_SETSIG:
356 /* arg == 0 restores default behaviour. */
357 if (!valid_signal(arg)) {
358 break;
359 }
360 err = 0;
361 filp->f_owner.signum = arg;
362 break;
363 case F_GETLEASE:
364 err = fcntl_getlease(filp);
365 break;
366 case F_SETLEASE:
367 err = fcntl_setlease(fd, filp, arg);
368 break;
369 case F_NOTIFY:
370 err = fcntl_dirnotify(fd, filp, arg);
371 break;
372 default:
373 break;
374 }
375 return err;
376 }
377
378 asmlinkage long sys_fcntl(unsigned int fd, unsigned int cmd, unsigned long arg)
379 {
380 struct file *filp;
381 long err = -EBADF;
382
383 filp = fget(fd);
384 if (!filp)
385 goto out;
386
387 err = security_file_fcntl(filp, cmd, arg);
388 if (err) {
389 fput(filp);
390 return err;
391 }
392
393 err = do_fcntl(fd, cmd, arg, filp);
394
395 fput(filp);
396 out:
397 return err;
398 }
399
400 #if BITS_PER_LONG == 32
401 asmlinkage long sys_fcntl64(unsigned int fd, unsigned int cmd, unsigned long arg)
402 {
403 struct file * filp;
404 long err;
405
406 err = -EBADF;
407 filp = fget(fd);
408 if (!filp)
409 goto out;
410
411 err = security_file_fcntl(filp, cmd, arg);
412 if (err) {
413 fput(filp);
414 return err;
415 }
416 err = -EBADF;
417
418 switch (cmd) {
419 case F_GETLK64:
420 err = fcntl_getlk64(filp, (struct flock64 __user *) arg);
421 break;
422 case F_SETLK64:
423 case F_SETLKW64:
424 err = fcntl_setlk64(fd, filp, cmd,
425 (struct flock64 __user *) arg);
426 break;
427 default:
428 err = do_fcntl(fd, cmd, arg, filp);
429 break;
430 }
431 fput(filp);
432 out:
433 return err;
434 }
435 #endif
436
437 /* Table to convert sigio signal codes into poll band bitmaps */
438
439 static const long band_table[NSIGPOLL] = {
440 POLLIN | POLLRDNORM, /* POLL_IN */
441 POLLOUT | POLLWRNORM | POLLWRBAND, /* POLL_OUT */
442 POLLIN | POLLRDNORM | POLLMSG, /* POLL_MSG */
443 POLLERR, /* POLL_ERR */
444 POLLPRI | POLLRDBAND, /* POLL_PRI */
445 POLLHUP | POLLERR /* POLL_HUP */
446 };
447
448 static inline int sigio_perm(struct task_struct *p,
449 struct fown_struct *fown, int sig)
450 {
451 return (((fown->euid == 0) ||
452 (fown->euid == p->suid) || (fown->euid == p->uid) ||
453 (fown->uid == p->suid) || (fown->uid == p->uid)) &&
454 !security_file_send_sigiotask(p, fown, sig));
455 }
456
457 static void send_sigio_to_task(struct task_struct *p,
458 struct fown_struct *fown,
459 int fd,
460 int reason)
461 {
462 if (!sigio_perm(p, fown, fown->signum))
463 return;
464
465 switch (fown->signum) {
466 siginfo_t si;
467 default:
468 /* Queue a rt signal with the appropriate fd as its
469 value. We use SI_SIGIO as the source, not
470 SI_KERNEL, since kernel signals always get
471 delivered even if we can't queue. Failure to
472 queue in this case _should_ be reported; we fall
473 back to SIGIO in that case. --sct */
474 si.si_signo = fown->signum;
475 si.si_errno = 0;
476 si.si_code = reason;
477 /* Make sure we are called with one of the POLL_*
478 reasons, otherwise we could leak kernel stack into
479 userspace. */
480 BUG_ON((reason & __SI_MASK) != __SI_POLL);
481 if (reason - POLL_IN >= NSIGPOLL)
482 si.si_band = ~0L;
483 else
484 si.si_band = band_table[reason - POLL_IN];
485 si.si_fd = fd;
486 if (!group_send_sig_info(fown->signum, &si, p))
487 break;
488 /* fall-through: fall back on the old plain SIGIO signal */
489 case 0:
490 group_send_sig_info(SIGIO, SEND_SIG_PRIV, p);
491 }
492 }
493
494 void send_sigio(struct fown_struct *fown, int fd, int band)
495 {
496 struct task_struct *p;
497 enum pid_type type;
498 struct pid *pid;
499
500 read_lock(&fown->lock);
501 type = fown->pid_type;
502 pid = fown->pid;
503 if (!pid)
504 goto out_unlock_fown;
505
506 read_lock(&tasklist_lock);
507 do_each_pid_task(pid, type, p) {
508 send_sigio_to_task(p, fown, fd, band);
509 } while_each_pid_task(pid, type, p);
510 read_unlock(&tasklist_lock);
511 out_unlock_fown:
512 read_unlock(&fown->lock);
513 }
514
515 static void send_sigurg_to_task(struct task_struct *p,
516 struct fown_struct *fown)
517 {
518 if (sigio_perm(p, fown, SIGURG))
519 group_send_sig_info(SIGURG, SEND_SIG_PRIV, p);
520 }
521
522 int send_sigurg(struct fown_struct *fown)
523 {
524 struct task_struct *p;
525 enum pid_type type;
526 struct pid *pid;
527 int ret = 0;
528
529 read_lock(&fown->lock);
530 type = fown->pid_type;
531 pid = fown->pid;
532 if (!pid)
533 goto out_unlock_fown;
534
535 ret = 1;
536
537 read_lock(&tasklist_lock);
538 do_each_pid_task(pid, type, p) {
539 send_sigurg_to_task(p, fown);
540 } while_each_pid_task(pid, type, p);
541 read_unlock(&tasklist_lock);
542 out_unlock_fown:
543 read_unlock(&fown->lock);
544 return ret;
545 }
546
547 static DEFINE_RWLOCK(fasync_lock);
548 static struct kmem_cache *fasync_cache __read_mostly;
549
550 /*
551 * fasync_helper() is used by some character device drivers (mainly mice)
552 * to set up the fasync queue. It returns negative on error, 0 if it did
553 * no changes and positive if it added/deleted the entry.
554 */
555 int fasync_helper(int fd, struct file * filp, int on, struct fasync_struct **fapp)
556 {
557 struct fasync_struct *fa, **fp;
558 struct fasync_struct *new = NULL;
559 int result = 0;
560
561 if (on) {
562 new = kmem_cache_alloc(fasync_cache, GFP_KERNEL);
563 if (!new)
564 return -ENOMEM;
565 }
566 write_lock_irq(&fasync_lock);
567 for (fp = fapp; (fa = *fp) != NULL; fp = &fa->fa_next) {
568 if (fa->fa_file == filp) {
569 if(on) {
570 fa->fa_fd = fd;
571 kmem_cache_free(fasync_cache, new);
572 } else {
573 *fp = fa->fa_next;
574 kmem_cache_free(fasync_cache, fa);
575 result = 1;
576 }
577 goto out;
578 }
579 }
580
581 if (on) {
582 new->magic = FASYNC_MAGIC;
583 new->fa_file = filp;
584 new->fa_fd = fd;
585 new->fa_next = *fapp;
586 *fapp = new;
587 result = 1;
588 }
589 out:
590 write_unlock_irq(&fasync_lock);
591 return result;
592 }
593
594 EXPORT_SYMBOL(fasync_helper);
595
596 void __kill_fasync(struct fasync_struct *fa, int sig, int band)
597 {
598 while (fa) {
599 struct fown_struct * fown;
600 if (fa->magic != FASYNC_MAGIC) {
601 printk(KERN_ERR "kill_fasync: bad magic number in "
602 "fasync_struct!\n");
603 return;
604 }
605 fown = &fa->fa_file->f_owner;
606 /* Don't send SIGURG to processes which have not set a
607 queued signum: SIGURG has its own default signalling
608 mechanism. */
609 if (!(sig == SIGURG && fown->signum == 0))
610 send_sigio(fown, fa->fa_fd, band);
611 fa = fa->fa_next;
612 }
613 }
614
615 EXPORT_SYMBOL(__kill_fasync);
616
617 void kill_fasync(struct fasync_struct **fp, int sig, int band)
618 {
619 /* First a quick test without locking: usually
620 * the list is empty.
621 */
622 if (*fp) {
623 read_lock(&fasync_lock);
624 /* reread *fp after obtaining the lock */
625 __kill_fasync(*fp, sig, band);
626 read_unlock(&fasync_lock);
627 }
628 }
629 EXPORT_SYMBOL(kill_fasync);
630
631 static int __init fasync_init(void)
632 {
633 fasync_cache = kmem_cache_create("fasync_cache",
634 sizeof(struct fasync_struct), 0, SLAB_PANIC, NULL);
635 return 0;
636 }
637
638 module_init(fasync_init)