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 rewritten 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(fse: old_fsn);
38 new = INOTIFY_E(fse: 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 fsnotify_group *group,
50 struct fsnotify_event *event)
51{
52 struct list_head *list = &group->notification_list;
53 struct fsnotify_event *last_event;
54
55 last_event = list_entry(list->prev, struct fsnotify_event, list);
56 return event_compare(old_fsn: last_event, new_fsn: event);
57}
58
59int inotify_handle_inode_event(struct fsnotify_mark *inode_mark, u32 mask,
60 struct inode *inode, struct inode *dir,
61 const struct qstr *name, u32 cookie)
62{
63 struct inotify_inode_mark *i_mark;
64 struct inotify_event_info *event;
65 struct fsnotify_event *fsn_event;
66 struct fsnotify_group *group = inode_mark->group;
67 int ret;
68 int len = 0, wd;
69 int alloc_len = sizeof(struct inotify_event_info);
70 struct mem_cgroup *old_memcg;
71
72 if (name) {
73 len = name->len;
74 alloc_len += len + 1;
75 }
76
77 pr_debug("%s: group=%p mark=%p mask=%x\n", __func__, group, inode_mark,
78 mask);
79
80 i_mark = container_of(inode_mark, struct inotify_inode_mark,
81 fsn_mark);
82
83 /*
84 * We can be racing with mark being detached. Don't report event with
85 * invalid wd.
86 */
87 wd = READ_ONCE(i_mark->wd);
88 if (wd == -1)
89 return 0;
90 /*
91 * Whoever is interested in the event, pays for the allocation. Do not
92 * trigger OOM killer in the target monitoring memcg as it may have
93 * security repercussion.
94 */
95 old_memcg = set_active_memcg(group->memcg);
96 event = kmalloc(alloc_len, GFP_KERNEL_ACCOUNT | __GFP_RETRY_MAYFAIL);
97 set_active_memcg(old_memcg);
98
99 if (unlikely(!event)) {
100 /*
101 * Treat lost event due to ENOMEM the same way as queue
102 * overflow to let userspace know event was lost.
103 */
104 fsnotify_queue_overflow(group);
105 return -ENOMEM;
106 }
107
108 /*
109 * We now report FS_ISDIR flag with MOVE_SELF and DELETE_SELF events
110 * for fanotify. inotify never reported IN_ISDIR with those events.
111 * It looks like an oversight, but to avoid the risk of breaking
112 * existing inotify programs, mask the flag out from those events.
113 */
114 if (mask & (IN_MOVE_SELF | IN_DELETE_SELF))
115 mask &= ~IN_ISDIR;
116
117 fsn_event = &event->fse;
118 fsnotify_init_event(event: fsn_event);
119 event->mask = mask;
120 event->wd = wd;
121 event->sync_cookie = cookie;
122 event->name_len = len;
123 if (len)
124 strscpy(event->name, name->name, event->name_len + 1);
125
126 ret = fsnotify_add_event(group, event: fsn_event, merge: inotify_merge);
127 if (ret) {
128 /* Our event wasn't used in the end. Free it. */
129 fsnotify_destroy_event(group, event: fsn_event);
130 }
131
132 if (inode_mark->flags & FSNOTIFY_MARK_FLAG_IN_ONESHOT)
133 fsnotify_destroy_mark(mark: inode_mark, group);
134
135 return 0;
136}
137
138static void inotify_freeing_mark(struct fsnotify_mark *fsn_mark, struct fsnotify_group *group)
139{
140 inotify_ignored_and_remove_idr(fsn_mark, group);
141}
142
143/*
144 * This is NEVER supposed to be called. Inotify marks should either have been
145 * removed from the idr when the watch was removed or in the
146 * fsnotify_destroy_mark_by_group() call when the inotify instance was being
147 * torn down. This is only called if the idr is about to be freed but there
148 * are still marks in it.
149 */
150static int idr_callback(int id, void *p, void *data)
151{
152 struct fsnotify_mark *fsn_mark;
153 struct inotify_inode_mark *i_mark;
154 static bool warned = false;
155
156 if (warned)
157 return 0;
158
159 warned = true;
160 fsn_mark = p;
161 i_mark = container_of(fsn_mark, struct inotify_inode_mark, fsn_mark);
162
163 WARN(1, "inotify closing but id=%d for fsn_mark=%p in group=%p still in "
164 "idr. Probably leaking memory\n", id, p, data);
165
166 /*
167 * I'm taking the liberty of assuming that the mark in question is a
168 * valid address and I'm dereferencing it. This might help to figure
169 * out why we got here and the panic is no worse than the original
170 * BUG() that was here.
171 */
172 if (fsn_mark)
173 printk(KERN_WARNING "fsn_mark->group=%p wd=%d\n",
174 fsn_mark->group, i_mark->wd);
175 return 0;
176}
177
178static void inotify_free_group_priv(struct fsnotify_group *group)
179{
180 /* ideally the idr is empty and we won't hit the BUG in the callback */
181 idr_for_each(&group->inotify_data.idr, fn: idr_callback, data: group);
182 idr_destroy(&group->inotify_data.idr);
183 if (group->inotify_data.ucounts)
184 dec_inotify_instances(ucounts: group->inotify_data.ucounts);
185}
186
187static void inotify_free_event(struct fsnotify_group *group,
188 struct fsnotify_event *fsn_event)
189{
190 kfree(objp: INOTIFY_E(fse: fsn_event));
191}
192
193/* ding dong the mark is dead */
194static void inotify_free_mark(struct fsnotify_mark *fsn_mark)
195{
196 struct inotify_inode_mark *i_mark;
197
198 i_mark = container_of(fsn_mark, struct inotify_inode_mark, fsn_mark);
199
200 kmem_cache_free(s: inotify_inode_mark_cachep, objp: i_mark);
201}
202
203const struct fsnotify_ops inotify_fsnotify_ops = {
204 .handle_inode_event = inotify_handle_inode_event,
205 .free_group_priv = inotify_free_group_priv,
206 .free_event = inotify_free_event,
207 .freeing_mark = inotify_freeing_mark,
208 .free_mark = inotify_free_mark,
209};
210

source code of linux/fs/notify/inotify/inotify_fsnotify.c