1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * fs/inotify_user.c - inotify support for userspace
4 *
5 * Authors:
6 *	John McCutchan	<ttb@tentacle.dhs.org>
7 *	Robert Love	<rml@novell.com>
8 *
9 * Copyright (C) 2005 John McCutchan
10 * Copyright 2006 Hewlett-Packard Development Company, L.P.
11 *
12 * Copyright (C) 2009 Eric Paris <Red Hat Inc>
13 * inotify was largely rewriten to make use of the fsnotify infrastructure
14 */
15
16#include <linux/dcache.h> /* d_unlinked */
17#include <linux/fs.h> /* struct inode */
18#include <linux/fsnotify_backend.h>
19#include <linux/inotify.h>
20#include <linux/path.h> /* struct path */
21#include <linux/slab.h> /* kmem_* */
22#include <linux/types.h>
23#include <linux/sched.h>
24#include <linux/sched/user.h>
25#include <linux/sched/mm.h>
26
27#include "inotify.h"
28
29/*
30 * Check if 2 events contain the same information.
31 */
32static bool event_compare(struct fsnotify_event *old_fsn,
33			  struct fsnotify_event *new_fsn)
34{
35	struct inotify_event_info *old, *new;
36
37	old = INOTIFY_E(old_fsn);
38	new = INOTIFY_E(new_fsn);
39	if (old->mask & FS_IN_IGNORED)
40		return false;
41	if ((old->mask == new->mask) &&
42	    (old->wd == new->wd) &&
43	    (old->name_len == new->name_len) &&
44	    (!old->name_len || !strcmp(old->name, new->name)))
45		return true;
46	return false;
47}
48
49static int inotify_merge(struct list_head *list,
50			  struct fsnotify_event *event)
51{
52	struct fsnotify_event *last_event;
53
54	last_event = list_entry(list->prev, struct fsnotify_event, list);
55	return event_compare(last_event, event);
56}
57
58int inotify_handle_inode_event(struct fsnotify_mark *inode_mark, u32 mask,
59			       struct inode *inode, struct inode *dir,
60			       const struct qstr *name, u32 cookie)
61{
62	struct inotify_inode_mark *i_mark;
63	struct inotify_event_info *event;
64	struct fsnotify_event *fsn_event;
65	struct fsnotify_group *group = inode_mark->group;
66	int ret;
67	int len = 0, wd;
68	int alloc_len = sizeof(struct inotify_event_info);
69	struct mem_cgroup *old_memcg;
70
71	if (name) {
72		len = name->len;
73		alloc_len += len + 1;
74	}
75
76	pr_debug("%s: group=%p mark=%p mask=%x\n", __func__, group, inode_mark,
77		 mask);
78
79	i_mark = container_of(inode_mark, struct inotify_inode_mark,
80			      fsn_mark);
81
82	/*
83	 * We can be racing with mark being detached. Don't report event with
84	 * invalid wd.
85	 */
86	wd = READ_ONCE(i_mark->wd);
87	if (wd == -1)
88		return 0;
89	/*
90	 * Whoever is interested in the event, pays for the allocation. Do not
91	 * trigger OOM killer in the target monitoring memcg as it may have
92	 * security repercussion.
93	 */
94	old_memcg = set_active_memcg(group->memcg);
95	event = kmalloc(alloc_len, GFP_KERNEL_ACCOUNT | __GFP_RETRY_MAYFAIL);
96	set_active_memcg(old_memcg);
97
98	if (unlikely(!event)) {
99		/*
100		 * Treat lost event due to ENOMEM the same way as queue
101		 * overflow to let userspace know event was lost.
102		 */
103		fsnotify_queue_overflow(group);
104		return -ENOMEM;
105	}
106
107	/*
108	 * We now report FS_ISDIR flag with MOVE_SELF and DELETE_SELF events
109	 * for fanotify. inotify never reported IN_ISDIR with those events.
110	 * It looks like an oversight, but to avoid the risk of breaking
111	 * existing inotify programs, mask the flag out from those events.
112	 */
113	if (mask & (IN_MOVE_SELF | IN_DELETE_SELF))
114		mask &= ~IN_ISDIR;
115
116	fsn_event = &event->fse;
117	fsnotify_init_event(fsn_event, 0);
118	event->mask = mask;
119	event->wd = wd;
120	event->sync_cookie = cookie;
121	event->name_len = len;
122	if (len)
123		strcpy(event->name, name->name);
124
125	ret = fsnotify_add_event(group, fsn_event, inotify_merge);
126	if (ret) {
127		/* Our event wasn't used in the end. Free it. */
128		fsnotify_destroy_event(group, fsn_event);
129	}
130
131	if (inode_mark->mask & IN_ONESHOT)
132		fsnotify_destroy_mark(inode_mark, group);
133
134	return 0;
135}
136
137static void inotify_freeing_mark(struct fsnotify_mark *fsn_mark, struct fsnotify_group *group)
138{
139	inotify_ignored_and_remove_idr(fsn_mark, group);
140}
141
142/*
143 * This is NEVER supposed to be called.  Inotify marks should either have been
144 * removed from the idr when the watch was removed or in the
145 * fsnotify_destroy_mark_by_group() call when the inotify instance was being
146 * torn down.  This is only called if the idr is about to be freed but there
147 * are still marks in it.
148 */
149static int idr_callback(int id, void *p, void *data)
150{
151	struct fsnotify_mark *fsn_mark;
152	struct inotify_inode_mark *i_mark;
153	static bool warned = false;
154
155	if (warned)
156		return 0;
157
158	warned = true;
159	fsn_mark = p;
160	i_mark = container_of(fsn_mark, struct inotify_inode_mark, fsn_mark);
161
162	WARN(1, "inotify closing but id=%d for fsn_mark=%p in group=%p still in "
163		"idr.  Probably leaking memory\n", id, p, data);
164
165	/*
166	 * I'm taking the liberty of assuming that the mark in question is a
167	 * valid address and I'm dereferencing it.  This might help to figure
168	 * out why we got here and the panic is no worse than the original
169	 * BUG() that was here.
170	 */
171	if (fsn_mark)
172		printk(KERN_WARNING "fsn_mark->group=%p wd=%d\n",
173			fsn_mark->group, i_mark->wd);
174	return 0;
175}
176
177static void inotify_free_group_priv(struct fsnotify_group *group)
178{
179	/* ideally the idr is empty and we won't hit the BUG in the callback */
180	idr_for_each(&group->inotify_data.idr, idr_callback, group);
181	idr_destroy(&group->inotify_data.idr);
182	if (group->inotify_data.ucounts)
183		dec_inotify_instances(group->inotify_data.ucounts);
184}
185
186static void inotify_free_event(struct fsnotify_event *fsn_event)
187{
188	kfree(INOTIFY_E(fsn_event));
189}
190
191/* ding dong the mark is dead */
192static void inotify_free_mark(struct fsnotify_mark *fsn_mark)
193{
194	struct inotify_inode_mark *i_mark;
195
196	i_mark = container_of(fsn_mark, struct inotify_inode_mark, fsn_mark);
197
198	kmem_cache_free(inotify_inode_mark_cachep, i_mark);
199}
200
201const struct fsnotify_ops inotify_fsnotify_ops = {
202	.handle_inode_event = inotify_handle_inode_event,
203	.free_group_priv = inotify_free_group_priv,
204	.free_event = inotify_free_event,
205	.freeing_mark = inotify_freeing_mark,
206	.free_mark = inotify_free_mark,
207};
208