1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3  * Copyright 1997-1998 Transmeta Corporation -- All Rights Reserved
4  * Copyright 2001-2006 Ian Kent <raven@themaw.net>
5  */
6 
7 #include <linux/sched/signal.h>
8 #include "autofs_i.h"
9 
10 /* We make this a static variable rather than a part of the superblock; it
11  * is better if we don't reassign numbers easily even across filesystems
12  */
13 static autofs_wqt_t autofs_next_wait_queue = 1;
14 
autofs_catatonic_mode(struct autofs_sb_info * sbi)15 void autofs_catatonic_mode(struct autofs_sb_info *sbi)
16 {
17 	struct autofs_wait_queue *wq, *nwq;
18 
19 	mutex_lock(&sbi->wq_mutex);
20 	if (sbi->flags & AUTOFS_SBI_CATATONIC) {
21 		mutex_unlock(&sbi->wq_mutex);
22 		return;
23 	}
24 
25 	pr_debug("entering catatonic mode\n");
26 
27 	sbi->flags |= AUTOFS_SBI_CATATONIC;
28 	wq = sbi->queues;
29 	sbi->queues = NULL;	/* Erase all wait queues */
30 	while (wq) {
31 		nwq = wq->next;
32 		wq->status = -ENOENT; /* Magic is gone - report failure */
33 		kfree(wq->name.name - wq->offset);
34 		wq->name.name = NULL;
35 		wq->wait_ctr--;
36 		wake_up_interruptible(&wq->queue);
37 		wq = nwq;
38 	}
39 	fput(sbi->pipe);	/* Close the pipe */
40 	sbi->pipe = NULL;
41 	sbi->pipefd = -1;
42 	mutex_unlock(&sbi->wq_mutex);
43 }
44 
autofs_write(struct autofs_sb_info * sbi,struct file * file,const void * addr,int bytes)45 static int autofs_write(struct autofs_sb_info *sbi,
46 			struct file *file, const void *addr, int bytes)
47 {
48 	unsigned long sigpipe, flags;
49 	const char *data = (const char *)addr;
50 	ssize_t wr = 0;
51 
52 	sigpipe = sigismember(&current->pending.signal, SIGPIPE);
53 
54 	mutex_lock(&sbi->pipe_mutex);
55 	while (bytes) {
56 		wr = __kernel_write(file, data, bytes, NULL);
57 		if (wr <= 0)
58 			break;
59 		data += wr;
60 		bytes -= wr;
61 	}
62 	mutex_unlock(&sbi->pipe_mutex);
63 
64 	/* Keep the currently executing process from receiving a
65 	 * SIGPIPE unless it was already supposed to get one
66 	 */
67 	if (wr == -EPIPE && !sigpipe) {
68 		spin_lock_irqsave(&current->sighand->siglock, flags);
69 		sigdelset(&current->pending.signal, SIGPIPE);
70 		recalc_sigpending();
71 		spin_unlock_irqrestore(&current->sighand->siglock, flags);
72 	}
73 
74 	/* if 'wr' returned 0 (impossible) we assume -EIO (safe) */
75 	return bytes == 0 ? 0 : wr < 0 ? wr : -EIO;
76 }
77 
autofs_notify_daemon(struct autofs_sb_info * sbi,struct autofs_wait_queue * wq,int type)78 static void autofs_notify_daemon(struct autofs_sb_info *sbi,
79 				 struct autofs_wait_queue *wq,
80 				 int type)
81 {
82 	union {
83 		struct autofs_packet_hdr hdr;
84 		union autofs_packet_union v4_pkt;
85 		union autofs_v5_packet_union v5_pkt;
86 	} pkt;
87 	struct file *pipe = NULL;
88 	size_t pktsz;
89 	int ret;
90 
91 	pr_debug("wait id = 0x%08lx, name = %.*s, type=%d\n",
92 		 (unsigned long) wq->wait_queue_token,
93 		 wq->name.len, wq->name.name, type);
94 
95 	memset(&pkt, 0, sizeof(pkt)); /* For security reasons */
96 
97 	pkt.hdr.proto_version = sbi->version;
98 	pkt.hdr.type = type;
99 
100 	switch (type) {
101 	/* Kernel protocol v4 missing and expire packets */
102 	case autofs_ptype_missing:
103 	{
104 		struct autofs_packet_missing *mp = &pkt.v4_pkt.missing;
105 
106 		pktsz = sizeof(*mp);
107 
108 		mp->wait_queue_token = wq->wait_queue_token;
109 		mp->len = wq->name.len;
110 		memcpy(mp->name, wq->name.name, wq->name.len);
111 		mp->name[wq->name.len] = '\0';
112 		break;
113 	}
114 	case autofs_ptype_expire_multi:
115 	{
116 		struct autofs_packet_expire_multi *ep =
117 					&pkt.v4_pkt.expire_multi;
118 
119 		pktsz = sizeof(*ep);
120 
121 		ep->wait_queue_token = wq->wait_queue_token;
122 		ep->len = wq->name.len;
123 		memcpy(ep->name, wq->name.name, wq->name.len);
124 		ep->name[wq->name.len] = '\0';
125 		break;
126 	}
127 	/*
128 	 * Kernel protocol v5 packet for handling indirect and direct
129 	 * mount missing and expire requests
130 	 */
131 	case autofs_ptype_missing_indirect:
132 	case autofs_ptype_expire_indirect:
133 	case autofs_ptype_missing_direct:
134 	case autofs_ptype_expire_direct:
135 	{
136 		struct autofs_v5_packet *packet = &pkt.v5_pkt.v5_packet;
137 		struct user_namespace *user_ns = sbi->pipe->f_cred->user_ns;
138 
139 		pktsz = sizeof(*packet);
140 
141 		packet->wait_queue_token = wq->wait_queue_token;
142 		packet->len = wq->name.len;
143 		memcpy(packet->name, wq->name.name, wq->name.len);
144 		packet->name[wq->name.len] = '\0';
145 		packet->dev = wq->dev;
146 		packet->ino = wq->ino;
147 		packet->uid = from_kuid_munged(user_ns, wq->uid);
148 		packet->gid = from_kgid_munged(user_ns, wq->gid);
149 		packet->pid = wq->pid;
150 		packet->tgid = wq->tgid;
151 		break;
152 	}
153 	default:
154 		pr_warn("bad type %d!\n", type);
155 		mutex_unlock(&sbi->wq_mutex);
156 		return;
157 	}
158 
159 	pipe = get_file(sbi->pipe);
160 
161 	mutex_unlock(&sbi->wq_mutex);
162 
163 	switch (ret = autofs_write(sbi, pipe, &pkt, pktsz)) {
164 	case 0:
165 		break;
166 	case -ENOMEM:
167 	case -ERESTARTSYS:
168 		/* Just fail this one */
169 		autofs_wait_release(sbi, wq->wait_queue_token, ret);
170 		break;
171 	default:
172 		autofs_catatonic_mode(sbi);
173 		break;
174 	}
175 	fput(pipe);
176 }
177 
178 static struct autofs_wait_queue *
autofs_find_wait(struct autofs_sb_info * sbi,const struct qstr * qstr)179 autofs_find_wait(struct autofs_sb_info *sbi, const struct qstr *qstr)
180 {
181 	struct autofs_wait_queue *wq;
182 
183 	for (wq = sbi->queues; wq; wq = wq->next) {
184 		if (wq->name.hash == qstr->hash &&
185 		    wq->name.len == qstr->len &&
186 		    wq->name.name &&
187 		    !memcmp(wq->name.name, qstr->name, qstr->len))
188 			break;
189 	}
190 	return wq;
191 }
192 
193 /*
194  * Check if we have a valid request.
195  * Returns
196  * 1 if the request should continue.
197  *   In this case we can return an autofs_wait_queue entry if one is
198  *   found or NULL to idicate a new wait needs to be created.
199  * 0 or a negative errno if the request shouldn't continue.
200  */
validate_request(struct autofs_wait_queue ** wait,struct autofs_sb_info * sbi,const struct qstr * qstr,const struct path * path,enum autofs_notify notify)201 static int validate_request(struct autofs_wait_queue **wait,
202 			    struct autofs_sb_info *sbi,
203 			    const struct qstr *qstr,
204 			    const struct path *path, enum autofs_notify notify)
205 {
206 	struct dentry *dentry = path->dentry;
207 	struct autofs_wait_queue *wq;
208 	struct autofs_info *ino;
209 
210 	if (sbi->flags & AUTOFS_SBI_CATATONIC)
211 		return -ENOENT;
212 
213 	/* Wait in progress, continue; */
214 	wq = autofs_find_wait(sbi, qstr);
215 	if (wq) {
216 		*wait = wq;
217 		return 1;
218 	}
219 
220 	*wait = NULL;
221 
222 	/* If we don't yet have any info this is a new request */
223 	ino = autofs_dentry_ino(dentry);
224 	if (!ino)
225 		return 1;
226 
227 	/*
228 	 * If we've been asked to wait on an existing expire (NFY_NONE)
229 	 * but there is no wait in the queue ...
230 	 */
231 	if (notify == NFY_NONE) {
232 		/*
233 		 * Either we've betean the pending expire to post it's
234 		 * wait or it finished while we waited on the mutex.
235 		 * So we need to wait till either, the wait appears
236 		 * or the expire finishes.
237 		 */
238 
239 		while (ino->flags & AUTOFS_INF_EXPIRING) {
240 			mutex_unlock(&sbi->wq_mutex);
241 			schedule_timeout_interruptible(HZ/10);
242 			if (mutex_lock_interruptible(&sbi->wq_mutex))
243 				return -EINTR;
244 
245 			if (sbi->flags & AUTOFS_SBI_CATATONIC)
246 				return -ENOENT;
247 
248 			wq = autofs_find_wait(sbi, qstr);
249 			if (wq) {
250 				*wait = wq;
251 				return 1;
252 			}
253 		}
254 
255 		/*
256 		 * Not ideal but the status has already gone. Of the two
257 		 * cases where we wait on NFY_NONE neither depend on the
258 		 * return status of the wait.
259 		 */
260 		return 0;
261 	}
262 
263 	/*
264 	 * If we've been asked to trigger a mount and the request
265 	 * completed while we waited on the mutex ...
266 	 */
267 	if (notify == NFY_MOUNT) {
268 		struct dentry *new = NULL;
269 		struct path this;
270 		int valid = 1;
271 
272 		/*
273 		 * If the dentry was successfully mounted while we slept
274 		 * on the wait queue mutex we can return success. If it
275 		 * isn't mounted (doesn't have submounts for the case of
276 		 * a multi-mount with no mount at it's base) we can
277 		 * continue on and create a new request.
278 		 */
279 		if (!IS_ROOT(dentry)) {
280 			if (d_unhashed(dentry) &&
281 			    d_really_is_positive(dentry)) {
282 				struct dentry *parent = dentry->d_parent;
283 
284 				new = d_lookup(parent, &dentry->d_name);
285 				if (new)
286 					dentry = new;
287 			}
288 		}
289 		this.mnt = path->mnt;
290 		this.dentry = dentry;
291 		if (path_has_submounts(&this))
292 			valid = 0;
293 
294 		if (new)
295 			dput(new);
296 		return valid;
297 	}
298 
299 	return 1;
300 }
301 
autofs_wait(struct autofs_sb_info * sbi,const struct path * path,enum autofs_notify notify)302 int autofs_wait(struct autofs_sb_info *sbi,
303 		 const struct path *path, enum autofs_notify notify)
304 {
305 	struct dentry *dentry = path->dentry;
306 	struct autofs_wait_queue *wq;
307 	struct qstr qstr;
308 	char *name;
309 	int status, ret, type;
310 	unsigned int offset = 0;
311 	pid_t pid;
312 	pid_t tgid;
313 
314 	/* In catatonic mode, we don't wait for nobody */
315 	if (sbi->flags & AUTOFS_SBI_CATATONIC)
316 		return -ENOENT;
317 
318 	/*
319 	 * Try translating pids to the namespace of the daemon.
320 	 *
321 	 * Zero means failure: we are in an unrelated pid namespace.
322 	 */
323 	pid = task_pid_nr_ns(current, ns_of_pid(sbi->oz_pgrp));
324 	tgid = task_tgid_nr_ns(current, ns_of_pid(sbi->oz_pgrp));
325 	if (pid == 0 || tgid == 0)
326 		return -ENOENT;
327 
328 	if (d_really_is_negative(dentry)) {
329 		/*
330 		 * A wait for a negative dentry is invalid for certain
331 		 * cases. A direct or offset mount "always" has its mount
332 		 * point directory created and so the request dentry must
333 		 * be positive or the map key doesn't exist. The situation
334 		 * is very similar for indirect mounts except only dentrys
335 		 * in the root of the autofs file system may be negative.
336 		 */
337 		if (autofs_type_trigger(sbi->type))
338 			return -ENOENT;
339 		else if (!IS_ROOT(dentry->d_parent))
340 			return -ENOENT;
341 	}
342 
343 	name = kmalloc(NAME_MAX + 1, GFP_KERNEL);
344 	if (!name)
345 		return -ENOMEM;
346 
347 	/* If this is a direct mount request create a dummy name */
348 	if (IS_ROOT(dentry) && autofs_type_trigger(sbi->type)) {
349 		qstr.name = name;
350 		qstr.len = sprintf(name, "%p", dentry);
351 	} else {
352 		char *p = dentry_path_raw(dentry, name, NAME_MAX);
353 		if (IS_ERR(p)) {
354 			kfree(name);
355 			return -ENOENT;
356 		}
357 		qstr.name = ++p; // skip the leading slash
358 		qstr.len = strlen(p);
359 		offset = p - name;
360 	}
361 	qstr.hash = full_name_hash(dentry, qstr.name, qstr.len);
362 
363 	if (mutex_lock_interruptible(&sbi->wq_mutex)) {
364 		kfree(name);
365 		return -EINTR;
366 	}
367 
368 	ret = validate_request(&wq, sbi, &qstr, path, notify);
369 	if (ret <= 0) {
370 		if (ret != -EINTR)
371 			mutex_unlock(&sbi->wq_mutex);
372 		kfree(name);
373 		return ret;
374 	}
375 
376 	if (!wq) {
377 		/* Create a new wait queue */
378 		wq = kmalloc(sizeof(struct autofs_wait_queue), GFP_KERNEL);
379 		if (!wq) {
380 			kfree(name);
381 			mutex_unlock(&sbi->wq_mutex);
382 			return -ENOMEM;
383 		}
384 
385 		wq->wait_queue_token = autofs_next_wait_queue;
386 		if (++autofs_next_wait_queue == 0)
387 			autofs_next_wait_queue = 1;
388 		wq->next = sbi->queues;
389 		sbi->queues = wq;
390 		init_waitqueue_head(&wq->queue);
391 		memcpy(&wq->name, &qstr, sizeof(struct qstr));
392 		wq->offset = offset;
393 		wq->dev = autofs_get_dev(sbi);
394 		wq->ino = autofs_get_ino(sbi);
395 		wq->uid = current_uid();
396 		wq->gid = current_gid();
397 		wq->pid = pid;
398 		wq->tgid = tgid;
399 		wq->status = -EINTR; /* Status return if interrupted */
400 		wq->wait_ctr = 2;
401 
402 		if (sbi->version < 5) {
403 			if (notify == NFY_MOUNT)
404 				type = autofs_ptype_missing;
405 			else
406 				type = autofs_ptype_expire_multi;
407 		} else {
408 			if (notify == NFY_MOUNT)
409 				type = autofs_type_trigger(sbi->type) ?
410 					autofs_ptype_missing_direct :
411 					 autofs_ptype_missing_indirect;
412 			else
413 				type = autofs_type_trigger(sbi->type) ?
414 					autofs_ptype_expire_direct :
415 					autofs_ptype_expire_indirect;
416 		}
417 
418 		pr_debug("new wait id = 0x%08lx, name = %.*s, nfy=%d\n",
419 			 (unsigned long) wq->wait_queue_token, wq->name.len,
420 			 wq->name.name, notify);
421 
422 		/*
423 		 * autofs_notify_daemon() may block; it will unlock ->wq_mutex
424 		 */
425 		autofs_notify_daemon(sbi, wq, type);
426 	} else {
427 		wq->wait_ctr++;
428 		pr_debug("existing wait id = 0x%08lx, name = %.*s, nfy=%d\n",
429 			 (unsigned long) wq->wait_queue_token, wq->name.len,
430 			 wq->name.name, notify);
431 		mutex_unlock(&sbi->wq_mutex);
432 		kfree(name);
433 	}
434 
435 	/*
436 	 * wq->name.name is NULL iff the lock is already released
437 	 * or the mount has been made catatonic.
438 	 */
439 	wait_event_killable(wq->queue, wq->name.name == NULL);
440 	status = wq->status;
441 
442 	/*
443 	 * For direct and offset mounts we need to track the requester's
444 	 * uid and gid in the dentry info struct. This is so it can be
445 	 * supplied, on request, by the misc device ioctl interface.
446 	 * This is needed during daemon resatart when reconnecting
447 	 * to existing, active, autofs mounts. The uid and gid (and
448 	 * related string values) may be used for macro substitution
449 	 * in autofs mount maps.
450 	 */
451 	if (!status) {
452 		struct autofs_info *ino;
453 		struct dentry *de = NULL;
454 
455 		/* direct mount or browsable map */
456 		ino = autofs_dentry_ino(dentry);
457 		if (!ino) {
458 			/* If not lookup actual dentry used */
459 			de = d_lookup(dentry->d_parent, &dentry->d_name);
460 			if (de)
461 				ino = autofs_dentry_ino(de);
462 		}
463 
464 		/* Set mount requester */
465 		if (ino) {
466 			spin_lock(&sbi->fs_lock);
467 			ino->uid = wq->uid;
468 			ino->gid = wq->gid;
469 			spin_unlock(&sbi->fs_lock);
470 		}
471 
472 		if (de)
473 			dput(de);
474 	}
475 
476 	/* Are we the last process to need status? */
477 	mutex_lock(&sbi->wq_mutex);
478 	if (!--wq->wait_ctr)
479 		kfree(wq);
480 	mutex_unlock(&sbi->wq_mutex);
481 
482 	return status;
483 }
484 
485 
autofs_wait_release(struct autofs_sb_info * sbi,autofs_wqt_t wait_queue_token,int status)486 int autofs_wait_release(struct autofs_sb_info *sbi,
487 			autofs_wqt_t wait_queue_token, int status)
488 {
489 	struct autofs_wait_queue *wq, **wql;
490 
491 	mutex_lock(&sbi->wq_mutex);
492 	for (wql = &sbi->queues; (wq = *wql) != NULL; wql = &wq->next) {
493 		if (wq->wait_queue_token == wait_queue_token)
494 			break;
495 	}
496 
497 	if (!wq) {
498 		mutex_unlock(&sbi->wq_mutex);
499 		return -EINVAL;
500 	}
501 
502 	*wql = wq->next;	/* Unlink from chain */
503 	kfree(wq->name.name - wq->offset);
504 	wq->name.name = NULL;	/* Do not wait on this queue */
505 	wq->status = status;
506 	wake_up(&wq->queue);
507 	if (!--wq->wait_ctr)
508 		kfree(wq);
509 	mutex_unlock(&sbi->wq_mutex);
510 
511 	return 0;
512 }
513