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  */
32 static 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_fsn->inode == new_fsn->inode) &&
43 	    (old->name_len == new->name_len) &&
44 	    (!old->name_len || !strcmp(old->name, new->name)))
45 		return true;
46 	return false;
47 }
48 
49 static 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 
58 int inotify_handle_event(struct fsnotify_group *group,
59 			 struct inode *inode,
60 			 u32 mask, const void *data, int data_type,
61 			 const struct qstr *file_name, u32 cookie,
62 			 struct fsnotify_iter_info *iter_info)
63 {
64 	struct fsnotify_mark *inode_mark = fsnotify_iter_inode_mark(iter_info);
65 	struct inotify_inode_mark *i_mark;
66 	struct inotify_event_info *event;
67 	struct fsnotify_event *fsn_event;
68 	int ret;
69 	int len = 0;
70 	int alloc_len = sizeof(struct inotify_event_info);
71 
72 	if (WARN_ON(fsnotify_iter_vfsmount_mark(iter_info)))
73 		return 0;
74 
75 	if ((inode_mark->mask & FS_EXCL_UNLINK) &&
76 	    (data_type == FSNOTIFY_EVENT_PATH)) {
77 		const struct path *path = data;
78 
79 		if (d_unlinked(path->dentry))
80 			return 0;
81 	}
82 	if (file_name) {
83 		len = file_name->len;
84 		alloc_len += len + 1;
85 	}
86 
87 	pr_debug("%s: group=%p inode=%p mask=%x\n", __func__, group, inode,
88 		 mask);
89 
90 	i_mark = container_of(inode_mark, struct inotify_inode_mark,
91 			      fsn_mark);
92 
93 	/*
94 	 * Whoever is interested in the event, pays for the allocation. Do not
95 	 * trigger OOM killer in the target monitoring memcg as it may have
96 	 * security repercussion.
97 	 */
98 	memalloc_use_memcg(group->memcg);
99 	event = kmalloc(alloc_len, GFP_KERNEL_ACCOUNT | __GFP_RETRY_MAYFAIL);
100 	memalloc_unuse_memcg();
101 
102 	if (unlikely(!event)) {
103 		/*
104 		 * Treat lost event due to ENOMEM the same way as queue
105 		 * overflow to let userspace know event was lost.
106 		 */
107 		fsnotify_queue_overflow(group);
108 		return -ENOMEM;
109 	}
110 
111 	/*
112 	 * We now report FS_ISDIR flag with MOVE_SELF and DELETE_SELF events
113 	 * for fanotify. inotify never reported IN_ISDIR with those events.
114 	 * It looks like an oversight, but to avoid the risk of breaking
115 	 * existing inotify programs, mask the flag out from those events.
116 	 */
117 	if (mask & (IN_MOVE_SELF | IN_DELETE_SELF))
118 		mask &= ~IN_ISDIR;
119 
120 	fsn_event = &event->fse;
121 	fsnotify_init_event(fsn_event, inode);
122 	event->mask = mask;
123 	event->wd = i_mark->wd;
124 	event->sync_cookie = cookie;
125 	event->name_len = len;
126 	if (len)
127 		strcpy(event->name, file_name->name);
128 
129 	ret = fsnotify_add_event(group, fsn_event, inotify_merge);
130 	if (ret) {
131 		/* Our event wasn't used in the end. Free it. */
132 		fsnotify_destroy_event(group, fsn_event);
133 	}
134 
135 	if (inode_mark->mask & IN_ONESHOT)
136 		fsnotify_destroy_mark(inode_mark, group);
137 
138 	return 0;
139 }
140 
141 static void inotify_freeing_mark(struct fsnotify_mark *fsn_mark, struct fsnotify_group *group)
142 {
143 	inotify_ignored_and_remove_idr(fsn_mark, group);
144 }
145 
146 /*
147  * This is NEVER supposed to be called.  Inotify marks should either have been
148  * removed from the idr when the watch was removed or in the
149  * fsnotify_destroy_mark_by_group() call when the inotify instance was being
150  * torn down.  This is only called if the idr is about to be freed but there
151  * are still marks in it.
152  */
153 static int idr_callback(int id, void *p, void *data)
154 {
155 	struct fsnotify_mark *fsn_mark;
156 	struct inotify_inode_mark *i_mark;
157 	static bool warned = false;
158 
159 	if (warned)
160 		return 0;
161 
162 	warned = true;
163 	fsn_mark = p;
164 	i_mark = container_of(fsn_mark, struct inotify_inode_mark, fsn_mark);
165 
166 	WARN(1, "inotify closing but id=%d for fsn_mark=%p in group=%p still in "
167 		"idr.  Probably leaking memory\n", id, p, data);
168 
169 	/*
170 	 * I'm taking the liberty of assuming that the mark in question is a
171 	 * valid address and I'm dereferencing it.  This might help to figure
172 	 * out why we got here and the panic is no worse than the original
173 	 * BUG() that was here.
174 	 */
175 	if (fsn_mark)
176 		printk(KERN_WARNING "fsn_mark->group=%p wd=%d\n",
177 			fsn_mark->group, i_mark->wd);
178 	return 0;
179 }
180 
181 static void inotify_free_group_priv(struct fsnotify_group *group)
182 {
183 	/* ideally the idr is empty and we won't hit the BUG in the callback */
184 	idr_for_each(&group->inotify_data.idr, idr_callback, group);
185 	idr_destroy(&group->inotify_data.idr);
186 	if (group->inotify_data.ucounts)
187 		dec_inotify_instances(group->inotify_data.ucounts);
188 }
189 
190 static void inotify_free_event(struct fsnotify_event *fsn_event)
191 {
192 	kfree(INOTIFY_E(fsn_event));
193 }
194 
195 /* ding dong the mark is dead */
196 static void inotify_free_mark(struct fsnotify_mark *fsn_mark)
197 {
198 	struct inotify_inode_mark *i_mark;
199 
200 	i_mark = container_of(fsn_mark, struct inotify_inode_mark, fsn_mark);
201 
202 	kmem_cache_free(inotify_inode_mark_cachep, i_mark);
203 }
204 
205 const struct fsnotify_ops inotify_fsnotify_ops = {
206 	.handle_event = inotify_handle_event,
207 	.free_group_priv = inotify_free_group_priv,
208 	.free_event = inotify_free_event,
209 	.freeing_mark = inotify_freeing_mark,
210 	.free_mark = inotify_free_mark,
211 };
212