xref: /linux/fs/fcntl.c (revision f3d9478b2ce468c3115b02ecae7e975990697f15) 
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, unsigned long pid,
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 		filp->f_owner.pid = pid;
259 		filp->f_owner.uid = uid;
260 		filp->f_owner.euid = euid;
261 	}
262 	write_unlock_irq(&filp->f_owner.lock);
263 }
264 
265 int f_setown(struct file *filp, unsigned long arg, int force)
266 {
267 	int err;
268 
269 	err = security_file_set_fowner(filp);
270 	if (err)
271 		return err;
272 
273 	f_modown(filp, arg, current->uid, current->euid, force);
274 	return 0;
275 }
276 
277 EXPORT_SYMBOL(f_setown);
278 
279 void f_delown(struct file *filp)
280 {
281 	f_modown(filp, 0, 0, 0, 1);
282 }
283 
284 static long do_fcntl(int fd, unsigned int cmd, unsigned long arg,
285 		struct file *filp)
286 {
287 	long err = -EINVAL;
288 
289 	switch (cmd) {
290 	case F_DUPFD:
291 		get_file(filp);
292 		err = dupfd(filp, arg);
293 		break;
294 	case F_GETFD:
295 		err = get_close_on_exec(fd) ? FD_CLOEXEC : 0;
296 		break;
297 	case F_SETFD:
298 		err = 0;
299 		set_close_on_exec(fd, arg & FD_CLOEXEC);
300 		break;
301 	case F_GETFL:
302 		err = filp->f_flags;
303 		break;
304 	case F_SETFL:
305 		err = setfl(fd, filp, arg);
306 		break;
307 	case F_GETLK:
308 		err = fcntl_getlk(filp, (struct flock __user *) arg);
309 		break;
310 	case F_SETLK:
311 	case F_SETLKW:
312 		err = fcntl_setlk(fd, filp, cmd, (struct flock __user *) arg);
313 		break;
314 	case F_GETOWN:
315 		/*
316 		 * XXX If f_owner is a process group, the
317 		 * negative return value will get converted
318 		 * into an error.  Oops.  If we keep the
319 		 * current syscall conventions, the only way
320 		 * to fix this will be in libc.
321 		 */
322 		err = filp->f_owner.pid;
323 		force_successful_syscall_return();
324 		break;
325 	case F_SETOWN:
326 		err = f_setown(filp, arg, 1);
327 		break;
328 	case F_GETSIG:
329 		err = filp->f_owner.signum;
330 		break;
331 	case F_SETSIG:
332 		/* arg == 0 restores default behaviour. */
333 		if (!valid_signal(arg)) {
334 			break;
335 		}
336 		err = 0;
337 		filp->f_owner.signum = arg;
338 		break;
339 	case F_GETLEASE:
340 		err = fcntl_getlease(filp);
341 		break;
342 	case F_SETLEASE:
343 		err = fcntl_setlease(fd, filp, arg);
344 		break;
345 	case F_NOTIFY:
346 		err = fcntl_dirnotify(fd, filp, arg);
347 		break;
348 	default:
349 		break;
350 	}
351 	return err;
352 }
353 
354 asmlinkage long sys_fcntl(unsigned int fd, unsigned int cmd, unsigned long arg)
355 {
356 	struct file *filp;
357 	long err = -EBADF;
358 
359 	filp = fget(fd);
360 	if (!filp)
361 		goto out;
362 
363 	err = security_file_fcntl(filp, cmd, arg);
364 	if (err) {
365 		fput(filp);
366 		return err;
367 	}
368 
369 	err = do_fcntl(fd, cmd, arg, filp);
370 
371  	fput(filp);
372 out:
373 	return err;
374 }
375 
376 #if BITS_PER_LONG == 32
377 asmlinkage long sys_fcntl64(unsigned int fd, unsigned int cmd, unsigned long arg)
378 {
379 	struct file * filp;
380 	long err;
381 
382 	err = -EBADF;
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 	err = -EBADF;
393 
394 	switch (cmd) {
395 		case F_GETLK64:
396 			err = fcntl_getlk64(filp, (struct flock64 __user *) arg);
397 			break;
398 		case F_SETLK64:
399 		case F_SETLKW64:
400 			err = fcntl_setlk64(fd, filp, cmd,
401 					(struct flock64 __user *) arg);
402 			break;
403 		default:
404 			err = do_fcntl(fd, cmd, arg, filp);
405 			break;
406 	}
407 	fput(filp);
408 out:
409 	return err;
410 }
411 #endif
412 
413 /* Table to convert sigio signal codes into poll band bitmaps */
414 
415 static const long band_table[NSIGPOLL] = {
416 	POLLIN | POLLRDNORM,			/* POLL_IN */
417 	POLLOUT | POLLWRNORM | POLLWRBAND,	/* POLL_OUT */
418 	POLLIN | POLLRDNORM | POLLMSG,		/* POLL_MSG */
419 	POLLERR,				/* POLL_ERR */
420 	POLLPRI | POLLRDBAND,			/* POLL_PRI */
421 	POLLHUP | POLLERR			/* POLL_HUP */
422 };
423 
424 static inline int sigio_perm(struct task_struct *p,
425                              struct fown_struct *fown, int sig)
426 {
427 	return (((fown->euid == 0) ||
428 		 (fown->euid == p->suid) || (fown->euid == p->uid) ||
429 		 (fown->uid == p->suid) || (fown->uid == p->uid)) &&
430 		!security_file_send_sigiotask(p, fown, sig));
431 }
432 
433 static void send_sigio_to_task(struct task_struct *p,
434 			       struct fown_struct *fown,
435 			       int fd,
436 			       int reason)
437 {
438 	if (!sigio_perm(p, fown, fown->signum))
439 		return;
440 
441 	switch (fown->signum) {
442 		siginfo_t si;
443 		default:
444 			/* Queue a rt signal with the appropriate fd as its
445 			   value.  We use SI_SIGIO as the source, not
446 			   SI_KERNEL, since kernel signals always get
447 			   delivered even if we can't queue.  Failure to
448 			   queue in this case _should_ be reported; we fall
449 			   back to SIGIO in that case. --sct */
450 			si.si_signo = fown->signum;
451 			si.si_errno = 0;
452 		        si.si_code  = reason;
453 			/* Make sure we are called with one of the POLL_*
454 			   reasons, otherwise we could leak kernel stack into
455 			   userspace.  */
456 			BUG_ON((reason & __SI_MASK) != __SI_POLL);
457 			if (reason - POLL_IN >= NSIGPOLL)
458 				si.si_band  = ~0L;
459 			else
460 				si.si_band = band_table[reason - POLL_IN];
461 			si.si_fd    = fd;
462 			if (!group_send_sig_info(fown->signum, &si, p))
463 				break;
464 		/* fall-through: fall back on the old plain SIGIO signal */
465 		case 0:
466 			group_send_sig_info(SIGIO, SEND_SIG_PRIV, p);
467 	}
468 }
469 
470 void send_sigio(struct fown_struct *fown, int fd, int band)
471 {
472 	struct task_struct *p;
473 	int pid;
474 
475 	read_lock(&fown->lock);
476 	pid = fown->pid;
477 	if (!pid)
478 		goto out_unlock_fown;
479 
480 	read_lock(&tasklist_lock);
481 	if (pid > 0) {
482 		p = find_task_by_pid(pid);
483 		if (p) {
484 			send_sigio_to_task(p, fown, fd, band);
485 		}
486 	} else {
487 		do_each_task_pid(-pid, PIDTYPE_PGID, p) {
488 			send_sigio_to_task(p, fown, fd, band);
489 		} while_each_task_pid(-pid, PIDTYPE_PGID, p);
490 	}
491 	read_unlock(&tasklist_lock);
492  out_unlock_fown:
493 	read_unlock(&fown->lock);
494 }
495 
496 static void send_sigurg_to_task(struct task_struct *p,
497                                 struct fown_struct *fown)
498 {
499 	if (sigio_perm(p, fown, SIGURG))
500 		group_send_sig_info(SIGURG, SEND_SIG_PRIV, p);
501 }
502 
503 int send_sigurg(struct fown_struct *fown)
504 {
505 	struct task_struct *p;
506 	int pid, ret = 0;
507 
508 	read_lock(&fown->lock);
509 	pid = fown->pid;
510 	if (!pid)
511 		goto out_unlock_fown;
512 
513 	ret = 1;
514 
515 	read_lock(&tasklist_lock);
516 	if (pid > 0) {
517 		p = find_task_by_pid(pid);
518 		if (p) {
519 			send_sigurg_to_task(p, fown);
520 		}
521 	} else {
522 		do_each_task_pid(-pid, PIDTYPE_PGID, p) {
523 			send_sigurg_to_task(p, fown);
524 		} while_each_task_pid(-pid, PIDTYPE_PGID, p);
525 	}
526 	read_unlock(&tasklist_lock);
527  out_unlock_fown:
528 	read_unlock(&fown->lock);
529 	return ret;
530 }
531 
532 static DEFINE_RWLOCK(fasync_lock);
533 static kmem_cache_t *fasync_cache __read_mostly;
534 
535 /*
536  * fasync_helper() is used by some character device drivers (mainly mice)
537  * to set up the fasync queue. It returns negative on error, 0 if it did
538  * no changes and positive if it added/deleted the entry.
539  */
540 int fasync_helper(int fd, struct file * filp, int on, struct fasync_struct **fapp)
541 {
542 	struct fasync_struct *fa, **fp;
543 	struct fasync_struct *new = NULL;
544 	int result = 0;
545 
546 	if (on) {
547 		new = kmem_cache_alloc(fasync_cache, SLAB_KERNEL);
548 		if (!new)
549 			return -ENOMEM;
550 	}
551 	write_lock_irq(&fasync_lock);
552 	for (fp = fapp; (fa = *fp) != NULL; fp = &fa->fa_next) {
553 		if (fa->fa_file == filp) {
554 			if(on) {
555 				fa->fa_fd = fd;
556 				kmem_cache_free(fasync_cache, new);
557 			} else {
558 				*fp = fa->fa_next;
559 				kmem_cache_free(fasync_cache, fa);
560 				result = 1;
561 			}
562 			goto out;
563 		}
564 	}
565 
566 	if (on) {
567 		new->magic = FASYNC_MAGIC;
568 		new->fa_file = filp;
569 		new->fa_fd = fd;
570 		new->fa_next = *fapp;
571 		*fapp = new;
572 		result = 1;
573 	}
574 out:
575 	write_unlock_irq(&fasync_lock);
576 	return result;
577 }
578 
579 EXPORT_SYMBOL(fasync_helper);
580 
581 void __kill_fasync(struct fasync_struct *fa, int sig, int band)
582 {
583 	while (fa) {
584 		struct fown_struct * fown;
585 		if (fa->magic != FASYNC_MAGIC) {
586 			printk(KERN_ERR "kill_fasync: bad magic number in "
587 			       "fasync_struct!\n");
588 			return;
589 		}
590 		fown = &fa->fa_file->f_owner;
591 		/* Don't send SIGURG to processes which have not set a
592 		   queued signum: SIGURG has its own default signalling
593 		   mechanism. */
594 		if (!(sig == SIGURG && fown->signum == 0))
595 			send_sigio(fown, fa->fa_fd, band);
596 		fa = fa->fa_next;
597 	}
598 }
599 
600 EXPORT_SYMBOL(__kill_fasync);
601 
602 void kill_fasync(struct fasync_struct **fp, int sig, int band)
603 {
604 	/* First a quick test without locking: usually
605 	 * the list is empty.
606 	 */
607 	if (*fp) {
608 		read_lock(&fasync_lock);
609 		/* reread *fp after obtaining the lock */
610 		__kill_fasync(*fp, sig, band);
611 		read_unlock(&fasync_lock);
612 	}
613 }
614 EXPORT_SYMBOL(kill_fasync);
615 
616 static int __init fasync_init(void)
617 {
618 	fasync_cache = kmem_cache_create("fasync_cache",
619 		sizeof(struct fasync_struct), 0, SLAB_PANIC, NULL, NULL);
620 	return 0;
621 }
622 
623 module_init(fasync_init)
624