xref: /openbmc/linux/fs/fcntl.c (revision 82ced6fd) 
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/fdtable.h>
13 #include <linux/capability.h>
14 #include <linux/dnotify.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 #include <linux/smp_lock.h>
23 
24 #include <asm/poll.h>
25 #include <asm/siginfo.h>
26 #include <asm/uaccess.h>
27 
28 void set_close_on_exec(unsigned int fd, int flag)
29 {
30 	struct files_struct *files = current->files;
31 	struct fdtable *fdt;
32 	spin_lock(&files->file_lock);
33 	fdt = files_fdtable(files);
34 	if (flag)
35 		FD_SET(fd, fdt->close_on_exec);
36 	else
37 		FD_CLR(fd, fdt->close_on_exec);
38 	spin_unlock(&files->file_lock);
39 }
40 
41 static int get_close_on_exec(unsigned int fd)
42 {
43 	struct files_struct *files = current->files;
44 	struct fdtable *fdt;
45 	int res;
46 	rcu_read_lock();
47 	fdt = files_fdtable(files);
48 	res = FD_ISSET(fd, fdt->close_on_exec);
49 	rcu_read_unlock();
50 	return res;
51 }
52 
53 SYSCALL_DEFINE3(dup3, unsigned int, oldfd, unsigned int, newfd, int, flags)
54 {
55 	int err = -EBADF;
56 	struct file * file, *tofree;
57 	struct files_struct * files = current->files;
58 	struct fdtable *fdt;
59 
60 	if ((flags & ~O_CLOEXEC) != 0)
61 		return -EINVAL;
62 
63 	if (unlikely(oldfd == newfd))
64 		return -EINVAL;
65 
66 	spin_lock(&files->file_lock);
67 	err = expand_files(files, newfd);
68 	file = fcheck(oldfd);
69 	if (unlikely(!file))
70 		goto Ebadf;
71 	if (unlikely(err < 0)) {
72 		if (err == -EMFILE)
73 			goto Ebadf;
74 		goto out_unlock;
75 	}
76 	/*
77 	 * We need to detect attempts to do dup2() over allocated but still
78 	 * not finished descriptor.  NB: OpenBSD avoids that at the price of
79 	 * extra work in their equivalent of fget() - they insert struct
80 	 * file immediately after grabbing descriptor, mark it larval if
81 	 * more work (e.g. actual opening) is needed and make sure that
82 	 * fget() treats larval files as absent.  Potentially interesting,
83 	 * but while extra work in fget() is trivial, locking implications
84 	 * and amount of surgery on open()-related paths in VFS are not.
85 	 * FreeBSD fails with -EBADF in the same situation, NetBSD "solution"
86 	 * deadlocks in rather amusing ways, AFAICS.  All of that is out of
87 	 * scope of POSIX or SUS, since neither considers shared descriptor
88 	 * tables and this condition does not arise without those.
89 	 */
90 	err = -EBUSY;
91 	fdt = files_fdtable(files);
92 	tofree = fdt->fd[newfd];
93 	if (!tofree && FD_ISSET(newfd, fdt->open_fds))
94 		goto out_unlock;
95 	get_file(file);
96 	rcu_assign_pointer(fdt->fd[newfd], file);
97 	FD_SET(newfd, fdt->open_fds);
98 	if (flags & O_CLOEXEC)
99 		FD_SET(newfd, fdt->close_on_exec);
100 	else
101 		FD_CLR(newfd, fdt->close_on_exec);
102 	spin_unlock(&files->file_lock);
103 
104 	if (tofree)
105 		filp_close(tofree, files);
106 
107 	return newfd;
108 
109 Ebadf:
110 	err = -EBADF;
111 out_unlock:
112 	spin_unlock(&files->file_lock);
113 	return err;
114 }
115 
116 SYSCALL_DEFINE2(dup2, unsigned int, oldfd, unsigned int, newfd)
117 {
118 	if (unlikely(newfd == oldfd)) { /* corner case */
119 		struct files_struct *files = current->files;
120 		int retval = oldfd;
121 
122 		rcu_read_lock();
123 		if (!fcheck_files(files, oldfd))
124 			retval = -EBADF;
125 		rcu_read_unlock();
126 		return retval;
127 	}
128 	return sys_dup3(oldfd, newfd, 0);
129 }
130 
131 SYSCALL_DEFINE1(dup, unsigned int, fildes)
132 {
133 	int ret = -EBADF;
134 	struct file *file = fget(fildes);
135 
136 	if (file) {
137 		ret = get_unused_fd();
138 		if (ret >= 0)
139 			fd_install(ret, file);
140 		else
141 			fput(file);
142 	}
143 	return ret;
144 }
145 
146 #define SETFL_MASK (O_APPEND | O_NONBLOCK | O_NDELAY | O_DIRECT | O_NOATIME)
147 
148 static int setfl(int fd, struct file * filp, unsigned long arg)
149 {
150 	struct inode * inode = filp->f_path.dentry->d_inode;
151 	int error = 0;
152 
153 	/*
154 	 * O_APPEND cannot be cleared if the file is marked as append-only
155 	 * and the file is open for write.
156 	 */
157 	if (((arg ^ filp->f_flags) & O_APPEND) && IS_APPEND(inode))
158 		return -EPERM;
159 
160 	/* O_NOATIME can only be set by the owner or superuser */
161 	if ((arg & O_NOATIME) && !(filp->f_flags & O_NOATIME))
162 		if (!is_owner_or_cap(inode))
163 			return -EPERM;
164 
165 	/* required for strict SunOS emulation */
166 	if (O_NONBLOCK != O_NDELAY)
167 	       if (arg & O_NDELAY)
168 		   arg |= O_NONBLOCK;
169 
170 	if (arg & O_DIRECT) {
171 		if (!filp->f_mapping || !filp->f_mapping->a_ops ||
172 			!filp->f_mapping->a_ops->direct_IO)
173 				return -EINVAL;
174 	}
175 
176 	if (filp->f_op && filp->f_op->check_flags)
177 		error = filp->f_op->check_flags(arg);
178 	if (error)
179 		return error;
180 
181 	/*
182 	 * ->fasync() is responsible for setting the FASYNC bit.
183 	 */
184 	if (((arg ^ filp->f_flags) & FASYNC) && filp->f_op &&
185 			filp->f_op->fasync) {
186 		error = filp->f_op->fasync(fd, filp, (arg & FASYNC) != 0);
187 		if (error < 0)
188 			goto out;
189 		if (error > 0)
190 			error = 0;
191 	}
192 	spin_lock(&filp->f_lock);
193 	filp->f_flags = (arg & SETFL_MASK) | (filp->f_flags & ~SETFL_MASK);
194 	spin_unlock(&filp->f_lock);
195 
196  out:
197 	return error;
198 }
199 
200 static void f_modown(struct file *filp, struct pid *pid, enum pid_type type,
201                      uid_t uid, uid_t euid, int force)
202 {
203 	write_lock_irq(&filp->f_owner.lock);
204 	if (force || !filp->f_owner.pid) {
205 		put_pid(filp->f_owner.pid);
206 		filp->f_owner.pid = get_pid(pid);
207 		filp->f_owner.pid_type = type;
208 		filp->f_owner.uid = uid;
209 		filp->f_owner.euid = euid;
210 	}
211 	write_unlock_irq(&filp->f_owner.lock);
212 }
213 
214 int __f_setown(struct file *filp, struct pid *pid, enum pid_type type,
215 		int force)
216 {
217 	const struct cred *cred = current_cred();
218 	int err;
219 
220 	err = security_file_set_fowner(filp);
221 	if (err)
222 		return err;
223 
224 	f_modown(filp, pid, type, cred->uid, cred->euid, force);
225 	return 0;
226 }
227 EXPORT_SYMBOL(__f_setown);
228 
229 int f_setown(struct file *filp, unsigned long arg, int force)
230 {
231 	enum pid_type type;
232 	struct pid *pid;
233 	int who = arg;
234 	int result;
235 	type = PIDTYPE_PID;
236 	if (who < 0) {
237 		type = PIDTYPE_PGID;
238 		who = -who;
239 	}
240 	rcu_read_lock();
241 	pid = find_vpid(who);
242 	result = __f_setown(filp, pid, type, force);
243 	rcu_read_unlock();
244 	return result;
245 }
246 EXPORT_SYMBOL(f_setown);
247 
248 void f_delown(struct file *filp)
249 {
250 	f_modown(filp, NULL, PIDTYPE_PID, 0, 0, 1);
251 }
252 
253 pid_t f_getown(struct file *filp)
254 {
255 	pid_t pid;
256 	read_lock(&filp->f_owner.lock);
257 	pid = pid_vnr(filp->f_owner.pid);
258 	if (filp->f_owner.pid_type == PIDTYPE_PGID)
259 		pid = -pid;
260 	read_unlock(&filp->f_owner.lock);
261 	return pid;
262 }
263 
264 static long do_fcntl(int fd, unsigned int cmd, unsigned long arg,
265 		struct file *filp)
266 {
267 	long err = -EINVAL;
268 
269 	switch (cmd) {
270 	case F_DUPFD:
271 	case F_DUPFD_CLOEXEC:
272 		if (arg >= current->signal->rlim[RLIMIT_NOFILE].rlim_cur)
273 			break;
274 		err = alloc_fd(arg, cmd == F_DUPFD_CLOEXEC ? O_CLOEXEC : 0);
275 		if (err >= 0) {
276 			get_file(filp);
277 			fd_install(err, filp);
278 		}
279 		break;
280 	case F_GETFD:
281 		err = get_close_on_exec(fd) ? FD_CLOEXEC : 0;
282 		break;
283 	case F_SETFD:
284 		err = 0;
285 		set_close_on_exec(fd, arg & FD_CLOEXEC);
286 		break;
287 	case F_GETFL:
288 		err = filp->f_flags;
289 		break;
290 	case F_SETFL:
291 		err = setfl(fd, filp, arg);
292 		break;
293 	case F_GETLK:
294 		err = fcntl_getlk(filp, (struct flock __user *) arg);
295 		break;
296 	case F_SETLK:
297 	case F_SETLKW:
298 		err = fcntl_setlk(fd, filp, cmd, (struct flock __user *) arg);
299 		break;
300 	case F_GETOWN:
301 		/*
302 		 * XXX If f_owner is a process group, the
303 		 * negative return value will get converted
304 		 * into an error.  Oops.  If we keep the
305 		 * current syscall conventions, the only way
306 		 * to fix this will be in libc.
307 		 */
308 		err = f_getown(filp);
309 		force_successful_syscall_return();
310 		break;
311 	case F_SETOWN:
312 		err = f_setown(filp, arg, 1);
313 		break;
314 	case F_GETSIG:
315 		err = filp->f_owner.signum;
316 		break;
317 	case F_SETSIG:
318 		/* arg == 0 restores default behaviour. */
319 		if (!valid_signal(arg)) {
320 			break;
321 		}
322 		err = 0;
323 		filp->f_owner.signum = arg;
324 		break;
325 	case F_GETLEASE:
326 		err = fcntl_getlease(filp);
327 		break;
328 	case F_SETLEASE:
329 		err = fcntl_setlease(fd, filp, arg);
330 		break;
331 	case F_NOTIFY:
332 		err = fcntl_dirnotify(fd, filp, arg);
333 		break;
334 	default:
335 		break;
336 	}
337 	return err;
338 }
339 
340 SYSCALL_DEFINE3(fcntl, unsigned int, fd, unsigned int, cmd, unsigned long, arg)
341 {
342 	struct file *filp;
343 	long err = -EBADF;
344 
345 	filp = fget(fd);
346 	if (!filp)
347 		goto out;
348 
349 	err = security_file_fcntl(filp, cmd, arg);
350 	if (err) {
351 		fput(filp);
352 		return err;
353 	}
354 
355 	err = do_fcntl(fd, cmd, arg, filp);
356 
357  	fput(filp);
358 out:
359 	return err;
360 }
361 
362 #if BITS_PER_LONG == 32
363 SYSCALL_DEFINE3(fcntl64, unsigned int, fd, unsigned int, cmd,
364 		unsigned long, arg)
365 {
366 	struct file * filp;
367 	long err;
368 
369 	err = -EBADF;
370 	filp = fget(fd);
371 	if (!filp)
372 		goto out;
373 
374 	err = security_file_fcntl(filp, cmd, arg);
375 	if (err) {
376 		fput(filp);
377 		return err;
378 	}
379 	err = -EBADF;
380 
381 	switch (cmd) {
382 		case F_GETLK64:
383 			err = fcntl_getlk64(filp, (struct flock64 __user *) arg);
384 			break;
385 		case F_SETLK64:
386 		case F_SETLKW64:
387 			err = fcntl_setlk64(fd, filp, cmd,
388 					(struct flock64 __user *) arg);
389 			break;
390 		default:
391 			err = do_fcntl(fd, cmd, arg, filp);
392 			break;
393 	}
394 	fput(filp);
395 out:
396 	return err;
397 }
398 #endif
399 
400 /* Table to convert sigio signal codes into poll band bitmaps */
401 
402 static const long band_table[NSIGPOLL] = {
403 	POLLIN | POLLRDNORM,			/* POLL_IN */
404 	POLLOUT | POLLWRNORM | POLLWRBAND,	/* POLL_OUT */
405 	POLLIN | POLLRDNORM | POLLMSG,		/* POLL_MSG */
406 	POLLERR,				/* POLL_ERR */
407 	POLLPRI | POLLRDBAND,			/* POLL_PRI */
408 	POLLHUP | POLLERR			/* POLL_HUP */
409 };
410 
411 static inline int sigio_perm(struct task_struct *p,
412                              struct fown_struct *fown, int sig)
413 {
414 	const struct cred *cred;
415 	int ret;
416 
417 	rcu_read_lock();
418 	cred = __task_cred(p);
419 	ret = ((fown->euid == 0 ||
420 		fown->euid == cred->suid || fown->euid == cred->uid ||
421 		fown->uid  == cred->suid || fown->uid  == cred->uid) &&
422 	       !security_file_send_sigiotask(p, fown, sig));
423 	rcu_read_unlock();
424 	return ret;
425 }
426 
427 static void send_sigio_to_task(struct task_struct *p,
428 			       struct fown_struct *fown,
429 			       int fd,
430 			       int reason)
431 {
432 	if (!sigio_perm(p, fown, fown->signum))
433 		return;
434 
435 	switch (fown->signum) {
436 		siginfo_t si;
437 		default:
438 			/* Queue a rt signal with the appropriate fd as its
439 			   value.  We use SI_SIGIO as the source, not
440 			   SI_KERNEL, since kernel signals always get
441 			   delivered even if we can't queue.  Failure to
442 			   queue in this case _should_ be reported; we fall
443 			   back to SIGIO in that case. --sct */
444 			si.si_signo = fown->signum;
445 			si.si_errno = 0;
446 		        si.si_code  = reason;
447 			/* Make sure we are called with one of the POLL_*
448 			   reasons, otherwise we could leak kernel stack into
449 			   userspace.  */
450 			BUG_ON((reason & __SI_MASK) != __SI_POLL);
451 			if (reason - POLL_IN >= NSIGPOLL)
452 				si.si_band  = ~0L;
453 			else
454 				si.si_band = band_table[reason - POLL_IN];
455 			si.si_fd    = fd;
456 			if (!group_send_sig_info(fown->signum, &si, p))
457 				break;
458 		/* fall-through: fall back on the old plain SIGIO signal */
459 		case 0:
460 			group_send_sig_info(SIGIO, SEND_SIG_PRIV, p);
461 	}
462 }
463 
464 void send_sigio(struct fown_struct *fown, int fd, int band)
465 {
466 	struct task_struct *p;
467 	enum pid_type type;
468 	struct pid *pid;
469 
470 	read_lock(&fown->lock);
471 	type = fown->pid_type;
472 	pid = fown->pid;
473 	if (!pid)
474 		goto out_unlock_fown;
475 
476 	read_lock(&tasklist_lock);
477 	do_each_pid_task(pid, type, p) {
478 		send_sigio_to_task(p, fown, fd, band);
479 	} while_each_pid_task(pid, type, p);
480 	read_unlock(&tasklist_lock);
481  out_unlock_fown:
482 	read_unlock(&fown->lock);
483 }
484 
485 static void send_sigurg_to_task(struct task_struct *p,
486                                 struct fown_struct *fown)
487 {
488 	if (sigio_perm(p, fown, SIGURG))
489 		group_send_sig_info(SIGURG, SEND_SIG_PRIV, p);
490 }
491 
492 int send_sigurg(struct fown_struct *fown)
493 {
494 	struct task_struct *p;
495 	enum pid_type type;
496 	struct pid *pid;
497 	int ret = 0;
498 
499 	read_lock(&fown->lock);
500 	type = fown->pid_type;
501 	pid = fown->pid;
502 	if (!pid)
503 		goto out_unlock_fown;
504 
505 	ret = 1;
506 
507 	read_lock(&tasklist_lock);
508 	do_each_pid_task(pid, type, p) {
509 		send_sigurg_to_task(p, fown);
510 	} while_each_pid_task(pid, type, p);
511 	read_unlock(&tasklist_lock);
512  out_unlock_fown:
513 	read_unlock(&fown->lock);
514 	return ret;
515 }
516 
517 static DEFINE_RWLOCK(fasync_lock);
518 static struct kmem_cache *fasync_cache __read_mostly;
519 
520 /*
521  * fasync_helper() is used by almost all character device drivers
522  * to set up the fasync queue. It returns negative on error, 0 if it did
523  * no changes and positive if it added/deleted the entry.
524  */
525 int fasync_helper(int fd, struct file * filp, int on, struct fasync_struct **fapp)
526 {
527 	struct fasync_struct *fa, **fp;
528 	struct fasync_struct *new = NULL;
529 	int result = 0;
530 
531 	if (on) {
532 		new = kmem_cache_alloc(fasync_cache, GFP_KERNEL);
533 		if (!new)
534 			return -ENOMEM;
535 	}
536 
537 	/*
538 	 * We need to take f_lock first since it's not an IRQ-safe
539 	 * lock.
540 	 */
541 	spin_lock(&filp->f_lock);
542 	write_lock_irq(&fasync_lock);
543 	for (fp = fapp; (fa = *fp) != NULL; fp = &fa->fa_next) {
544 		if (fa->fa_file == filp) {
545 			if(on) {
546 				fa->fa_fd = fd;
547 				kmem_cache_free(fasync_cache, new);
548 			} else {
549 				*fp = fa->fa_next;
550 				kmem_cache_free(fasync_cache, fa);
551 				result = 1;
552 			}
553 			goto out;
554 		}
555 	}
556 
557 	if (on) {
558 		new->magic = FASYNC_MAGIC;
559 		new->fa_file = filp;
560 		new->fa_fd = fd;
561 		new->fa_next = *fapp;
562 		*fapp = new;
563 		result = 1;
564 	}
565 out:
566 	if (on)
567 		filp->f_flags |= FASYNC;
568 	else
569 		filp->f_flags &= ~FASYNC;
570 	write_unlock_irq(&fasync_lock);
571 	spin_unlock(&filp->f_lock);
572 	return result;
573 }
574 
575 EXPORT_SYMBOL(fasync_helper);
576 
577 void __kill_fasync(struct fasync_struct *fa, int sig, int band)
578 {
579 	while (fa) {
580 		struct fown_struct * fown;
581 		if (fa->magic != FASYNC_MAGIC) {
582 			printk(KERN_ERR "kill_fasync: bad magic number in "
583 			       "fasync_struct!\n");
584 			return;
585 		}
586 		fown = &fa->fa_file->f_owner;
587 		/* Don't send SIGURG to processes which have not set a
588 		   queued signum: SIGURG has its own default signalling
589 		   mechanism. */
590 		if (!(sig == SIGURG && fown->signum == 0))
591 			send_sigio(fown, fa->fa_fd, band);
592 		fa = fa->fa_next;
593 	}
594 }
595 
596 EXPORT_SYMBOL(__kill_fasync);
597 
598 void kill_fasync(struct fasync_struct **fp, int sig, int band)
599 {
600 	/* First a quick test without locking: usually
601 	 * the list is empty.
602 	 */
603 	if (*fp) {
604 		read_lock(&fasync_lock);
605 		/* reread *fp after obtaining the lock */
606 		__kill_fasync(*fp, sig, band);
607 		read_unlock(&fasync_lock);
608 	}
609 }
610 EXPORT_SYMBOL(kill_fasync);
611 
612 static int __init fasync_init(void)
613 {
614 	fasync_cache = kmem_cache_create("fasync_cache",
615 		sizeof(struct fasync_struct), 0, SLAB_PANIC, NULL);
616 	return 0;
617 }
618 
619 module_init(fasync_init)
620