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 */
13static autofs_wqt_t autofs_next_wait_queue = 1;
14
15void 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		wake_up(&wq->queue);
36		if (!--wq->wait_ctr)
37			kfree(wq);
38		wq = nwq;
39	}
40	fput(sbi->pipe);	/* Close the pipe */
41	sbi->pipe = NULL;
42	sbi->pipefd = -1;
43	mutex_unlock(&sbi->wq_mutex);
44}
45
46static int autofs_write(struct autofs_sb_info *sbi,
47			struct file *file, const void *addr, int bytes)
48{
49	unsigned long sigpipe, flags;
50	const char *data = (const char *)addr;
51	ssize_t wr = 0;
52
53	sigpipe = sigismember(&current->pending.signal, SIGPIPE);
54
55	mutex_lock(&sbi->pipe_mutex);
56	while (bytes) {
57		wr = __kernel_write(file, data, bytes, NULL);
58		if (wr <= 0)
59			break;
60		data += wr;
61		bytes -= wr;
62	}
63	mutex_unlock(&sbi->pipe_mutex);
64
65	/* Keep the currently executing process from receiving a
66	 * SIGPIPE unless it was already supposed to get one
67	 */
68	if (wr == -EPIPE && !sigpipe) {
69		spin_lock_irqsave(&current->sighand->siglock, flags);
70		sigdelset(&current->pending.signal, SIGPIPE);
71		recalc_sigpending();
72		spin_unlock_irqrestore(&current->sighand->siglock, flags);
73	}
74
75	/* if 'wr' returned 0 (impossible) we assume -EIO (safe) */
76	return bytes == 0 ? 0 : wr < 0 ? wr : -EIO;
77}
78
79static void autofs_notify_daemon(struct autofs_sb_info *sbi,
80				 struct autofs_wait_queue *wq,
81				 int type)
82{
83	union {
84		struct autofs_packet_hdr hdr;
85		union autofs_packet_union v4_pkt;
86		union autofs_v5_packet_union v5_pkt;
87	} pkt;
88	struct file *pipe = NULL;
89	size_t pktsz;
90	int ret;
91
92	pr_debug("wait id = 0x%08lx, name = %.*s, type=%d\n",
93		 (unsigned long) wq->wait_queue_token,
94		 wq->name.len, wq->name.name, type);
95
96	memset(&pkt, 0, sizeof(pkt)); /* For security reasons */
97
98	pkt.hdr.proto_version = sbi->version;
99	pkt.hdr.type = type;
100
101	switch (type) {
102	/* Kernel protocol v4 missing and expire packets */
103	case autofs_ptype_missing:
104	{
105		struct autofs_packet_missing *mp = &pkt.v4_pkt.missing;
106
107		pktsz = sizeof(*mp);
108
109		mp->wait_queue_token = wq->wait_queue_token;
110		mp->len = wq->name.len;
111		memcpy(mp->name, wq->name.name, wq->name.len);
112		mp->name[wq->name.len] = '\0';
113		break;
114	}
115	case autofs_ptype_expire_multi:
116	{
117		struct autofs_packet_expire_multi *ep =
118					&pkt.v4_pkt.expire_multi;
119
120		pktsz = sizeof(*ep);
121
122		ep->wait_queue_token = wq->wait_queue_token;
123		ep->len = wq->name.len;
124		memcpy(ep->name, wq->name.name, wq->name.len);
125		ep->name[wq->name.len] = '\0';
126		break;
127	}
128	/*
129	 * Kernel protocol v5 packet for handling indirect and direct
130	 * mount missing and expire requests
131	 */
132	case autofs_ptype_missing_indirect:
133	case autofs_ptype_expire_indirect:
134	case autofs_ptype_missing_direct:
135	case autofs_ptype_expire_direct:
136	{
137		struct autofs_v5_packet *packet = &pkt.v5_pkt.v5_packet;
138		struct user_namespace *user_ns = sbi->pipe->f_cred->user_ns;
139
140		pktsz = sizeof(*packet);
141
142		packet->wait_queue_token = wq->wait_queue_token;
143		packet->len = wq->name.len;
144		memcpy(packet->name, wq->name.name, wq->name.len);
145		packet->name[wq->name.len] = '\0';
146		packet->dev = wq->dev;
147		packet->ino = wq->ino;
148		packet->uid = from_kuid_munged(user_ns, wq->uid);
149		packet->gid = from_kgid_munged(user_ns, wq->gid);
150		packet->pid = wq->pid;
151		packet->tgid = wq->tgid;
152		break;
153	}
154	default:
155		pr_warn("bad type %d!\n", type);
156		mutex_unlock(&sbi->wq_mutex);
157		return;
158	}
159
160	pipe = get_file(sbi->pipe);
161
162	mutex_unlock(&sbi->wq_mutex);
163
164	switch (ret = autofs_write(sbi, pipe, &pkt, pktsz)) {
165	case 0:
166		break;
167	case -ENOMEM:
168	case -ERESTARTSYS:
169		/* Just fail this one */
170		autofs_wait_release(sbi, wq->wait_queue_token, ret);
171		break;
172	default:
173		autofs_catatonic_mode(sbi);
174		break;
175	}
176	fput(pipe);
177}
178
179static struct autofs_wait_queue *
180autofs_find_wait(struct autofs_sb_info *sbi, const struct qstr *qstr)
181{
182	struct autofs_wait_queue *wq;
183
184	for (wq = sbi->queues; wq; wq = wq->next) {
185		if (wq->name.hash == qstr->hash &&
186		    wq->name.len == qstr->len &&
187		    wq->name.name &&
188		    !memcmp(wq->name.name, qstr->name, qstr->len))
189			break;
190	}
191	return wq;
192}
193
194/*
195 * Check if we have a valid request.
196 * Returns
197 * 1 if the request should continue.
198 *   In this case we can return an autofs_wait_queue entry if one is
199 *   found or NULL to idicate a new wait needs to be created.
200 * 0 or a negative errno if the request shouldn't continue.
201 */
202static int validate_request(struct autofs_wait_queue **wait,
203			    struct autofs_sb_info *sbi,
204			    const struct qstr *qstr,
205			    const struct path *path, enum autofs_notify notify)
206{
207	struct dentry *dentry = path->dentry;
208	struct autofs_wait_queue *wq;
209	struct autofs_info *ino;
210
211	if (sbi->flags & AUTOFS_SBI_CATATONIC)
212		return -ENOENT;
213
214	/* Wait in progress, continue; */
215	wq = autofs_find_wait(sbi, qstr);
216	if (wq) {
217		*wait = wq;
218		return 1;
219	}
220
221	*wait = NULL;
222
223	/* If we don't yet have any info this is a new request */
224	ino = autofs_dentry_ino(dentry);
225	if (!ino)
226		return 1;
227
228	/*
229	 * If we've been asked to wait on an existing expire (NFY_NONE)
230	 * but there is no wait in the queue ...
231	 */
232	if (notify == NFY_NONE) {
233		/*
234		 * Either we've betean the pending expire to post it's
235		 * wait or it finished while we waited on the mutex.
236		 * So we need to wait till either, the wait appears
237		 * or the expire finishes.
238		 */
239
240		while (ino->flags & AUTOFS_INF_EXPIRING) {
241			mutex_unlock(&sbi->wq_mutex);
242			schedule_timeout_interruptible(HZ/10);
243			if (mutex_lock_interruptible(&sbi->wq_mutex))
244				return -EINTR;
245
246			if (sbi->flags & AUTOFS_SBI_CATATONIC)
247				return -ENOENT;
248
249			wq = autofs_find_wait(sbi, qstr);
250			if (wq) {
251				*wait = wq;
252				return 1;
253			}
254		}
255
256		/*
257		 * Not ideal but the status has already gone. Of the two
258		 * cases where we wait on NFY_NONE neither depend on the
259		 * return status of the wait.
260		 */
261		return 0;
262	}
263
264	/*
265	 * If we've been asked to trigger a mount and the request
266	 * completed while we waited on the mutex ...
267	 */
268	if (notify == NFY_MOUNT) {
269		struct dentry *new = NULL;
270		struct path this;
271		int valid = 1;
272
273		/*
274		 * If the dentry was successfully mounted while we slept
275		 * on the wait queue mutex we can return success. If it
276		 * isn't mounted (doesn't have submounts for the case of
277		 * a multi-mount with no mount at it's base) we can
278		 * continue on and create a new request.
279		 */
280		if (!IS_ROOT(dentry)) {
281			if (d_unhashed(dentry) &&
282			    d_really_is_positive(dentry)) {
283				struct dentry *parent = dentry->d_parent;
284
285				new = d_lookup(parent, &dentry->d_name);
286				if (new)
287					dentry = new;
288			}
289		}
290		this.mnt = path->mnt;
291		this.dentry = dentry;
292		if (path_has_submounts(&this))
293			valid = 0;
294
295		if (new)
296			dput(new);
297		return valid;
298	}
299
300	return 1;
301}
302
303int autofs_wait(struct autofs_sb_info *sbi,
304		 const struct path *path, enum autofs_notify notify)
305{
306	struct dentry *dentry = path->dentry;
307	struct autofs_wait_queue *wq;
308	struct qstr qstr;
309	char *name;
310	int status, ret, type;
311	unsigned int offset = 0;
312	pid_t pid;
313	pid_t tgid;
314
315	/* In catatonic mode, we don't wait for nobody */
316	if (sbi->flags & AUTOFS_SBI_CATATONIC)
317		return -ENOENT;
318
319	/*
320	 * Try translating pids to the namespace of the daemon.
321	 *
322	 * Zero means failure: we are in an unrelated pid namespace.
323	 */
324	pid = task_pid_nr_ns(current, ns_of_pid(sbi->oz_pgrp));
325	tgid = task_tgid_nr_ns(current, ns_of_pid(sbi->oz_pgrp));
326	if (pid == 0 || tgid == 0)
327		return -ENOENT;
328
329	if (d_really_is_negative(dentry)) {
330		/*
331		 * A wait for a negative dentry is invalid for certain
332		 * cases. A direct or offset mount "always" has its mount
333		 * point directory created and so the request dentry must
334		 * be positive or the map key doesn't exist. The situation
335		 * is very similar for indirect mounts except only dentrys
336		 * in the root of the autofs file system may be negative.
337		 */
338		if (autofs_type_trigger(sbi->type))
339			return -ENOENT;
340		else if (!IS_ROOT(dentry->d_parent))
341			return -ENOENT;
342	}
343
344	name = kmalloc(NAME_MAX + 1, GFP_KERNEL);
345	if (!name)
346		return -ENOMEM;
347
348	/* If this is a direct mount request create a dummy name */
349	if (IS_ROOT(dentry) && autofs_type_trigger(sbi->type)) {
350		qstr.name = name;
351		qstr.len = sprintf(name, "%p", dentry);
352	} else {
353		char *p = dentry_path_raw(dentry, name, NAME_MAX);
354		if (IS_ERR(p)) {
355			kfree(name);
356			return -ENOENT;
357		}
358		qstr.name = ++p; // skip the leading slash
359		qstr.len = strlen(p);
360		offset = p - name;
361	}
362	qstr.hash = full_name_hash(dentry, qstr.name, qstr.len);
363
364	if (mutex_lock_interruptible(&sbi->wq_mutex)) {
365		kfree(name);
366		return -EINTR;
367	}
368
369	ret = validate_request(&wq, sbi, &qstr, path, notify);
370	if (ret <= 0) {
371		if (ret != -EINTR)
372			mutex_unlock(&sbi->wq_mutex);
373		kfree(name);
374		return ret;
375	}
376
377	if (!wq) {
378		/* Create a new wait queue */
379		wq = kmalloc(sizeof(struct autofs_wait_queue), GFP_KERNEL);
380		if (!wq) {
381			kfree(name);
382			mutex_unlock(&sbi->wq_mutex);
383			return -ENOMEM;
384		}
385
386		wq->wait_queue_token = autofs_next_wait_queue;
387		if (++autofs_next_wait_queue == 0)
388			autofs_next_wait_queue = 1;
389		wq->next = sbi->queues;
390		sbi->queues = wq;
391		init_waitqueue_head(&wq->queue);
392		memcpy(&wq->name, &qstr, sizeof(struct qstr));
393		wq->offset = offset;
394		wq->dev = autofs_get_dev(sbi);
395		wq->ino = autofs_get_ino(sbi);
396		wq->uid = current_uid();
397		wq->gid = current_gid();
398		wq->pid = pid;
399		wq->tgid = tgid;
400		wq->status = -EINTR; /* Status return if interrupted */
401		wq->wait_ctr = 2;
402
403		if (sbi->version < 5) {
404			if (notify == NFY_MOUNT)
405				type = autofs_ptype_missing;
406			else
407				type = autofs_ptype_expire_multi;
408		} else {
409			if (notify == NFY_MOUNT)
410				type = autofs_type_trigger(sbi->type) ?
411					autofs_ptype_missing_direct :
412					 autofs_ptype_missing_indirect;
413			else
414				type = autofs_type_trigger(sbi->type) ?
415					autofs_ptype_expire_direct :
416					autofs_ptype_expire_indirect;
417		}
418
419		pr_debug("new wait id = 0x%08lx, name = %.*s, nfy=%d\n",
420			 (unsigned long) wq->wait_queue_token, wq->name.len,
421			 wq->name.name, notify);
422
423		/*
424		 * autofs_notify_daemon() may block; it will unlock ->wq_mutex
425		 */
426		autofs_notify_daemon(sbi, wq, type);
427	} else {
428		wq->wait_ctr++;
429		pr_debug("existing wait id = 0x%08lx, name = %.*s, nfy=%d\n",
430			 (unsigned long) wq->wait_queue_token, wq->name.len,
431			 wq->name.name, notify);
432		mutex_unlock(&sbi->wq_mutex);
433		kfree(name);
434	}
435
436	/*
437	 * wq->name.name is NULL iff the lock is already released
438	 * or the mount has been made catatonic.
439	 */
440	wait_event_killable(wq->queue, wq->name.name == NULL);
441	status = wq->status;
442
443	/*
444	 * For direct and offset mounts we need to track the requester's
445	 * uid and gid in the dentry info struct. This is so it can be
446	 * supplied, on request, by the misc device ioctl interface.
447	 * This is needed during daemon resatart when reconnecting
448	 * to existing, active, autofs mounts. The uid and gid (and
449	 * related string values) may be used for macro substitution
450	 * in autofs mount maps.
451	 */
452	if (!status) {
453		struct autofs_info *ino;
454		struct dentry *de = NULL;
455
456		/* direct mount or browsable map */
457		ino = autofs_dentry_ino(dentry);
458		if (!ino) {
459			/* If not lookup actual dentry used */
460			de = d_lookup(dentry->d_parent, &dentry->d_name);
461			if (de)
462				ino = autofs_dentry_ino(de);
463		}
464
465		/* Set mount requester */
466		if (ino) {
467			spin_lock(&sbi->fs_lock);
468			ino->uid = wq->uid;
469			ino->gid = wq->gid;
470			spin_unlock(&sbi->fs_lock);
471		}
472
473		if (de)
474			dput(de);
475	}
476
477	/* Are we the last process to need status? */
478	mutex_lock(&sbi->wq_mutex);
479	if (!--wq->wait_ctr)
480		kfree(wq);
481	mutex_unlock(&sbi->wq_mutex);
482
483	return status;
484}
485
486
487int autofs_wait_release(struct autofs_sb_info *sbi,
488			autofs_wqt_t wait_queue_token, int status)
489{
490	struct autofs_wait_queue *wq, **wql;
491
492	mutex_lock(&sbi->wq_mutex);
493	for (wql = &sbi->queues; (wq = *wql) != NULL; wql = &wq->next) {
494		if (wq->wait_queue_token == wait_queue_token)
495			break;
496	}
497
498	if (!wq) {
499		mutex_unlock(&sbi->wq_mutex);
500		return -EINVAL;
501	}
502
503	*wql = wq->next;	/* Unlink from chain */
504	kfree(wq->name.name - wq->offset);
505	wq->name.name = NULL;	/* Do not wait on this queue */
506	wq->status = status;
507	wake_up(&wq->queue);
508	if (!--wq->wait_ctr)
509		kfree(wq);
510	mutex_unlock(&sbi->wq_mutex);
511
512	return 0;
513}
514