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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
22 #include <asm/poll.h>
23 #include <asm/siginfo.h>
24 #include <asm/uaccess.h>
25
26 void fastcall set_close_on_exec(unsigned int fd, int flag)
27 {
28 struct files_struct *files = current->files;
29 struct fdtable *fdt;
30 spin_lock(&files->file_lock);
31 fdt = files_fdtable(files);
32 if (flag)
33 FD_SET(fd, fdt->close_on_exec);
34 else
35 FD_CLR(fd, fdt->close_on_exec);
36 spin_unlock(&files->file_lock);
37 }
38
39 static int get_close_on_exec(unsigned int fd)
40 {
41 struct files_struct *files = current->files;
42 struct fdtable *fdt;
43 int res;
44 rcu_read_lock();
45 fdt = files_fdtable(files);
46 res = FD_ISSET(fd, fdt->close_on_exec);
47 rcu_read_unlock();
48 return res;
49 }
50
51 /*
52 * locate_fd finds a free file descriptor in the open_fds fdset,
53 * expanding the fd arrays if necessary. Must be called with the
54 * file_lock held for write.
55 */
56
57 static int locate_fd(struct files_struct *files,
58 struct file *file, unsigned int orig_start)
59 {
60 unsigned int newfd;
61 unsigned int start;
62 int error;
63 struct fdtable *fdt;
64
65 error = -EINVAL;
66 if (orig_start >= current->signal->rlim[RLIMIT_NOFILE].rlim_cur)
67 goto out;
68
69 repeat:
70 fdt = files_fdtable(files);
71 /*
72 * Someone might have closed fd's in the range
73 * orig_start..fdt->next_fd
74 */
75 start = orig_start;
76 if (start < files->next_fd)
77 start = files->next_fd;
78
79 newfd = start;
80 if (start < fdt->max_fdset) {
81 newfd = find_next_zero_bit(fdt->open_fds->fds_bits,
82 fdt->max_fdset, start);
83 }
84
85 error = -EMFILE;
86 if (newfd >= current->signal->rlim[RLIMIT_NOFILE].rlim_cur)
87 goto out;
88
89 error = expand_files(files, newfd);
90 if (error < 0)
91 goto out;
92
93 /*
94 * If we needed to expand the fs array we
95 * might have blocked - try again.
96 */
97 if (error)
98 goto repeat;
99
100 /*
101 * We reacquired files_lock, so we are safe as long as
102 * we reacquire the fdtable pointer and use it while holding
103 * the lock, no one can free it during that time.
104 */
105 if (start <= files->next_fd)
106 files->next_fd = newfd + 1;
107
108 error = newfd;
109
110 out:
111 return error;
112 }
113
114 static int dupfd(struct file *file, unsigned int start)
115 {
116 struct files_struct * files = current->files;
117 struct fdtable *fdt;
118 int fd;
119
120 spin_lock(&files->file_lock);
121 fd = locate_fd(files, file, start);
122 if (fd >= 0) {
123 /* locate_fd() may have expanded fdtable, load the ptr */
124 fdt = files_fdtable(files);
125 FD_SET(fd, fdt->open_fds);
126 FD_CLR(fd, fdt->close_on_exec);
127 spin_unlock(&files->file_lock);
128 fd_install(fd, file);
129 } else {
130 spin_unlock(&files->file_lock);
131 fput(file);
132 }
133
134 return fd;
135 }
136
137 asmlinkage long sys_dup2(unsigned int oldfd, unsigned int newfd)
138 {
139 int err = -EBADF;
140 struct file * file, *tofree;
141 struct files_struct * files = current->files;
142 struct fdtable *fdt;
143
144 spin_lock(&files->file_lock);
145 if (!(file = fcheck(oldfd)))
146 goto out_unlock;
147 err = newfd;
148 if (newfd == oldfd)
149 goto out_unlock;
150 err = -EBADF;
151 if (newfd >= current->signal->rlim[RLIMIT_NOFILE].rlim_cur)
152 goto out_unlock;
153 get_file(file); /* We are now finished with oldfd */
154
155 err = expand_files(files, newfd);
156 if (err < 0)
157 goto out_fput;
158
159 /* To avoid races with open() and dup(), we will mark the fd as
160 * in-use in the open-file bitmap throughout the entire dup2()
161 * process. This is quite safe: do_close() uses the fd array
162 * entry, not the bitmap, to decide what work needs to be
163 * done. --sct */
164 /* Doesn't work. open() might be there first. --AV */
165
166 /* Yes. It's a race. In user space. Nothing sane to do */
167 err = -EBUSY;
168 fdt = files_fdtable(files);
169 tofree = fdt->fd[newfd];
170 if (!tofree && FD_ISSET(newfd, fdt->open_fds))
171 goto out_fput;
172
173 rcu_assign_pointer(fdt->fd[newfd], file);
174 FD_SET(newfd, fdt->open_fds);
175 FD_CLR(newfd, fdt->close_on_exec);
176 spin_unlock(&files->file_lock);
177
178 if (tofree)
179 filp_close(tofree, files);
180 err = newfd;
181 out:
182 return err;
183 out_unlock:
184 spin_unlock(&files->file_lock);
185 goto out;
186
187 out_fput:
188 spin_unlock(&files->file_lock);
189 fput(file);
190 goto out;
191 }
192
193 asmlinkage long sys_dup(unsigned int fildes)
194 {
195 int ret = -EBADF;
196 struct file * file = fget(fildes);
197
198 if (file)
199 ret = dupfd(file, 0);
200 return ret;
201 }
202
203 #define SETFL_MASK (O_APPEND | O_NONBLOCK | O_NDELAY | FASYNC | O_DIRECT | O_NOATIME)
204
205 static int setfl(int fd, struct file * filp, unsigned long arg)
206 {
207 struct inode * inode = filp->f_dentry->d_inode;
208 int error = 0;
209
210 /*
211 * O_APPEND cannot be cleared if the file is marked as append-only
212 * and the file is open for write.
213 */
214 if (((arg ^ filp->f_flags) & O_APPEND) && IS_APPEND(inode))
215 return -EPERM;
216
217 /* O_NOATIME can only be set by the owner or superuser */
218 if ((arg & O_NOATIME) && !(filp->f_flags & O_NOATIME))
219 if (current->fsuid != inode->i_uid && !capable(CAP_FOWNER))
220 return -EPERM;
221
222 /* required for strict SunOS emulation */
223 if (O_NONBLOCK != O_NDELAY)
224 if (arg & O_NDELAY)
225 arg |= O_NONBLOCK;
226
227 if (arg & O_DIRECT) {
228 if (!filp->f_mapping || !filp->f_mapping->a_ops ||
229 !filp->f_mapping->a_ops->direct_IO)
230 return -EINVAL;
231 }
232
233 if (filp->f_op && filp->f_op->check_flags)
234 error = filp->f_op->check_flags(arg);
235 if (error)
236 return error;
237
238 lock_kernel();
239 if ((arg ^ filp->f_flags) & FASYNC) {
240 if (filp->f_op && filp->f_op->fasync) {
241 error = filp->f_op->fasync(fd, filp, (arg & FASYNC) != 0);
242 if (error < 0)
243 goto out;
244 }
245 }
246
247 filp->f_flags = (arg & SETFL_MASK) | (filp->f_flags & ~SETFL_MASK);
248 out:
249 unlock_kernel();
250 return error;
251 }
252
253 static void f_modown(struct file *filp, struct pid *pid, enum pid_type type,
254 uid_t uid, uid_t euid, int force)
255 {
256 write_lock_irq(&filp->f_owner.lock);
257 if (force || !filp->f_owner.pid) {
258 put_pid(filp->f_owner.pid);
259 filp->f_owner.pid = get_pid(pid);
260 filp->f_owner.pid_type = type;
261 filp->f_owner.uid = uid;
262 filp->f_owner.euid = euid;
263 }
264 write_unlock_irq(&filp->f_owner.lock);
265 }
266
267 int __f_setown(struct file *filp, struct pid *pid, enum pid_type type,
268 int force)
269 {
270 int err;
271
272 err = security_file_set_fowner(filp);
273 if (err)
274 return err;
275
276 f_modown(filp, pid, type, current->uid, current->euid, force);
277 return 0;
278 }
279 EXPORT_SYMBOL(__f_setown);
280
281 int f_setown(struct file *filp, unsigned long arg, int force)
282 {
283 enum pid_type type;
284 struct pid *pid;
285 int who = arg;
286 int result;
287 type = PIDTYPE_PID;
288 if (who < 0) {
289 type = PIDTYPE_PGID;
290 who = -who;
291 }
292 rcu_read_lock();
293 pid = find_pid(who);
294 result = __f_setown(filp, pid, type, force);
295 rcu_read_unlock();
296 return result;
297 }
298 EXPORT_SYMBOL(f_setown);
299
300 void f_delown(struct file *filp)
301 {
302 f_modown(filp, NULL, PIDTYPE_PID, 0, 0, 1);
303 }
304
305 pid_t f_getown(struct file *filp)
306 {
307 pid_t pid;
308 read_lock(&filp->f_owner.lock);
309 pid = pid_nr(filp->f_owner.pid);
310 if (filp->f_owner.pid_type == PIDTYPE_PGID)
311 pid = -pid;
312 read_unlock(&filp->f_owner.lock);
313 return pid;
314 }
315
316 static long do_fcntl(int fd, unsigned int cmd, unsigned long arg,
317 struct file *filp)
318 {
319 long err = -EINVAL;
320
321 switch (cmd) {
322 case F_DUPFD:
323 get_file(filp);
324 err = dupfd(filp, arg);
325 break;
326 case F_GETFD:
327 err = get_close_on_exec(fd) ? FD_CLOEXEC : 0;
328 break;
329 case F_SETFD:
330 err = 0;
331 set_close_on_exec(fd, arg & FD_CLOEXEC);
332 break;
333 case F_GETFL:
334 err = filp->f_flags;
335 break;
336 case F_SETFL:
337 err = setfl(fd, filp, arg);
338 break;
339 case F_GETLK:
340 err = fcntl_getlk(filp, (struct flock __user *) arg);
341 break;
342 case F_SETLK:
343 case F_SETLKW:
344 err = fcntl_setlk(fd, filp, cmd, (struct flock __user *) arg);
345 break;
346 case F_GETOWN:
347 /*
348 * XXX If f_owner is a process group, the
349 * negative return value will get converted
350 * into an error. Oops. If we keep the
351 * current syscall conventions, the only way
352 * to fix this will be in libc.
353 */
354 err = f_getown(filp);
355 force_successful_syscall_return();
356 break;
357 case F_SETOWN:
358 err = f_setown(filp, arg, 1);
359 break;
360 case F_GETSIG:
361 err = filp->f_owner.signum;
362 break;
363 case F_SETSIG:
364 /* arg == 0 restores default behaviour. */
365 if (!valid_signal(arg)) {
366 break;
367 }
368 err = 0;
369 filp->f_owner.signum = arg;
370 break;
371 case F_GETLEASE:
372 err = fcntl_getlease(filp);
373 break;
374 case F_SETLEASE:
375 err = fcntl_setlease(fd, filp, arg);
376 break;
377 case F_NOTIFY:
378 err = fcntl_dirnotify(fd, filp, arg);
379 break;
380 default:
381 break;
382 }
383 return err;
384 }
385
386 asmlinkage long sys_fcntl(unsigned int fd, unsigned int cmd, unsigned long arg)
387 {
388 struct file *filp;
389 long err = -EBADF;
390
391 filp = fget(fd);
392 if (!filp)
393 goto out;
394
395 err = security_file_fcntl(filp, cmd, arg);
396 if (err) {
397 fput(filp);
398 return err;
399 }
400
401 err = do_fcntl(fd, cmd, arg, filp);
402
403 fput(filp);
404 out:
405 return err;
406 }
407
408 #if BITS_PER_LONG == 32
409 asmlinkage long sys_fcntl64(unsigned int fd, unsigned int cmd, unsigned long arg)
410 {
411 struct file * filp;
412 long err;
413
414 err = -EBADF;
415 filp = fget(fd);
416 if (!filp)
417 goto out;
418
419 err = security_file_fcntl(filp, cmd, arg);
420 if (err) {
421 fput(filp);
422 return err;
423 }
424 err = -EBADF;
425
426 switch (cmd) {
427 case F_GETLK64:
428 err = fcntl_getlk64(filp, (struct flock64 __user *) arg);
429 break;
430 case F_SETLK64:
431 case F_SETLKW64:
432 err = fcntl_setlk64(fd, filp, cmd,
433 (struct flock64 __user *) arg);
434 break;
435 default:
436 err = do_fcntl(fd, cmd, arg, filp);
437 break;
438 }
439 fput(filp);
440 out:
441 return err;
442 }
443 #endif
444
445 /* Table to convert sigio signal codes into poll band bitmaps */
446
447 static const long band_table[NSIGPOLL] = {
448 POLLIN | POLLRDNORM, /* POLL_IN */
449 POLLOUT | POLLWRNORM | POLLWRBAND, /* POLL_OUT */
450 POLLIN | POLLRDNORM | POLLMSG, /* POLL_MSG */
451 POLLERR, /* POLL_ERR */
452 POLLPRI | POLLRDBAND, /* POLL_PRI */
453 POLLHUP | POLLERR /* POLL_HUP */
454 };
455
456 static inline int sigio_perm(struct task_struct *p,
457 struct fown_struct *fown, int sig)
458 {
459 return (((fown->euid == 0) ||
460 (fown->euid == p->suid) || (fown->euid == p->uid) ||
461 (fown->uid == p->suid) || (fown->uid == p->uid)) &&
462 !security_file_send_sigiotask(p, fown, sig));
463 }
464
465 static void send_sigio_to_task(struct task_struct *p,
466 struct fown_struct *fown,
467 int fd,
468 int reason)
469 {
470 if (!sigio_perm(p, fown, fown->signum))
471 return;
472
473 switch (fown->signum) {
474 siginfo_t si;
475 default:
476 /* Queue a rt signal with the appropriate fd as its
477 value. We use SI_SIGIO as the source, not
478 SI_KERNEL, since kernel signals always get
479 delivered even if we can't queue. Failure to
480 queue in this case _should_ be reported; we fall
481 back to SIGIO in that case. --sct */
482 si.si_signo = fown->signum;
483 si.si_errno = 0;
484 si.si_code = reason;
485 /* Make sure we are called with one of the POLL_*
486 reasons, otherwise we could leak kernel stack into
487 userspace. */
488 BUG_ON((reason & __SI_MASK) != __SI_POLL);
489 if (reason - POLL_IN >= NSIGPOLL)
490 si.si_band = ~0L;
491 else
492 si.si_band = band_table[reason - POLL_IN];
493 si.si_fd = fd;
494 if (!group_send_sig_info(fown->signum, &si, p))
495 break;
496 /* fall-through: fall back on the old plain SIGIO signal */
497 case 0:
498 group_send_sig_info(SIGIO, SEND_SIG_PRIV, p);
499 }
500 }
501
502 void send_sigio(struct fown_struct *fown, int fd, int band)
503 {
504 struct task_struct *p;
505 enum pid_type type;
506 struct pid *pid;
507
508 read_lock(&fown->lock);
509 type = fown->pid_type;
510 pid = fown->pid;
511 if (!pid)
512 goto out_unlock_fown;
513
514 read_lock(&tasklist_lock);
515 do_each_pid_task(pid, type, p) {
516 send_sigio_to_task(p, fown, fd, band);
517 } while_each_pid_task(pid, type, p);
518 read_unlock(&tasklist_lock);
519 out_unlock_fown:
520 read_unlock(&fown->lock);
521 }
522
523 static void send_sigurg_to_task(struct task_struct *p,
524 struct fown_struct *fown)
525 {
526 if (sigio_perm(p, fown, SIGURG))
527 group_send_sig_info(SIGURG, SEND_SIG_PRIV, p);
528 }
529
530 int send_sigurg(struct fown_struct *fown)
531 {
532 struct task_struct *p;
533 enum pid_type type;
534 struct pid *pid;
535 int ret = 0;
536
537 read_lock(&fown->lock);
538 type = fown->pid_type;
539 pid = fown->pid;
540 if (!pid)
541 goto out_unlock_fown;
542
543 ret = 1;
544
545 read_lock(&tasklist_lock);
546 do_each_pid_task(pid, type, p) {
547 send_sigurg_to_task(p, fown);
548 } while_each_pid_task(pid, type, p);
549 read_unlock(&tasklist_lock);
550 out_unlock_fown:
551 read_unlock(&fown->lock);
552 return ret;
553 }
554
555 static DEFINE_RWLOCK(fasync_lock);
556 static kmem_cache_t *fasync_cache __read_mostly;
557
558 /*
559 * fasync_helper() is used by some character device drivers (mainly mice)
560 * to set up the fasync queue. It returns negative on error, 0 if it did
561 * no changes and positive if it added/deleted the entry.
562 */
563 int fasync_helper(int fd, struct file * filp, int on, struct fasync_struct **fapp)
564 {
565 struct fasync_struct *fa, **fp;
566 struct fasync_struct *new = NULL;
567 int result = 0;
568
569 if (on) {
570 new = kmem_cache_alloc(fasync_cache, SLAB_KERNEL);
571 if (!new)
572 return -ENOMEM;
573 }
574 write_lock_irq(&fasync_lock);
575 for (fp = fapp; (fa = *fp) != NULL; fp = &fa->fa_next) {
576 if (fa->fa_file == filp) {
577 if(on) {
578 fa->fa_fd = fd;
579 kmem_cache_free(fasync_cache, new);
580 } else {
581 *fp = fa->fa_next;
582 kmem_cache_free(fasync_cache, fa);
583 result = 1;
584 }
585 goto out;
586 }
587 }
588
589 if (on) {
590 new->magic = FASYNC_MAGIC;
591 new->fa_file = filp;
592 new->fa_fd = fd;
593 new->fa_next = *fapp;
594 *fapp = new;
595 result = 1;
596 }
597 out:
598 write_unlock_irq(&fasync_lock);
599 return result;
600 }
601
602 EXPORT_SYMBOL(fasync_helper);
603
604 void __kill_fasync(struct fasync_struct *fa, int sig, int band)
605 {
606 while (fa) {
607 struct fown_struct * fown;
608 if (fa->magic != FASYNC_MAGIC) {
609 printk(KERN_ERR "kill_fasync: bad magic number in "
610 "fasync_struct!\n");
611 return;
612 }
613 fown = &fa->fa_file->f_owner;
614 /* Don't send SIGURG to processes which have not set a
615 queued signum: SIGURG has its own default signalling
616 mechanism. */
617 if (!(sig == SIGURG && fown->signum == 0))
618 send_sigio(fown, fa->fa_fd, band);
619 fa = fa->fa_next;
620 }
621 }
622
623 EXPORT_SYMBOL(__kill_fasync);
624
625 void kill_fasync(struct fasync_struct **fp, int sig, int band)
626 {
627 /* First a quick test without locking: usually
628 * the list is empty.
629 */
630 if (*fp) {
631 read_lock(&fasync_lock);
632 /* reread *fp after obtaining the lock */
633 __kill_fasync(*fp, sig, band);
634 read_unlock(&fasync_lock);
635 }
636 }
637 EXPORT_SYMBOL(kill_fasync);
638
639 static int __init fasync_init(void)
640 {
641 fasync_cache = kmem_cache_create("fasync_cache",
642 sizeof(struct fasync_struct), 0, SLAB_PANIC, NULL, NULL);
643 return 0;
644 }
645
646 module_init(fasync_init)