1 /*
2  * fs/inotify_user.c - inotify support for userspace
3  *
4  * Authors:
5  *	John McCutchan	<ttb@tentacle.dhs.org>
6  *	Robert Love	<rml@novell.com>
7  *
8  * Copyright (C) 2005 John McCutchan
9  * Copyright 2006 Hewlett-Packard Development Company, L.P.
10  *
11  * Copyright (C) 2009 Eric Paris <Red Hat Inc>
12  * inotify was largely rewriten to make use of the fsnotify infrastructure
13  *
14  * This program is free software; you can redistribute it and/or modify it
15  * under the terms of the GNU General Public License as published by the
16  * Free Software Foundation; either version 2, or (at your option) any
17  * later version.
18  *
19  * This program is distributed in the hope that it will be useful, but
20  * WITHOUT ANY WARRANTY; without even the implied warranty of
21  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
22  * General Public License for more details.
23  */
24 
25 #include <linux/dcache.h> /* d_unlinked */
26 #include <linux/fs.h> /* struct inode */
27 #include <linux/fsnotify_backend.h>
28 #include <linux/inotify.h>
29 #include <linux/path.h> /* struct path */
30 #include <linux/slab.h> /* kmem_* */
31 #include <linux/types.h>
32 #include <linux/sched.h>
33 
34 #include "inotify.h"
35 
36 /*
37  * Check if 2 events contain the same information.
38  */
39 static bool event_compare(struct fsnotify_event *old_fsn,
40 			  struct fsnotify_event *new_fsn)
41 {
42 	struct inotify_event_info *old, *new;
43 
44 	if (old_fsn->mask & FS_IN_IGNORED)
45 		return false;
46 	old = INOTIFY_E(old_fsn);
47 	new = INOTIFY_E(new_fsn);
48 	if ((old_fsn->mask == new_fsn->mask) &&
49 	    (old_fsn->inode == new_fsn->inode) &&
50 	    (old->name_len == new->name_len) &&
51 	    (!old->name_len || !strcmp(old->name, new->name)))
52 		return true;
53 	return false;
54 }
55 
56 static int inotify_merge(struct list_head *list,
57 			  struct fsnotify_event *event)
58 {
59 	struct fsnotify_event *last_event;
60 
61 	last_event = list_entry(list->prev, struct fsnotify_event, list);
62 	return event_compare(last_event, event);
63 }
64 
65 int inotify_handle_event(struct fsnotify_group *group,
66 			 struct inode *inode,
67 			 struct fsnotify_mark *inode_mark,
68 			 struct fsnotify_mark *vfsmount_mark,
69 			 u32 mask, void *data, int data_type,
70 			 const unsigned char *file_name, u32 cookie)
71 {
72 	struct inotify_inode_mark *i_mark;
73 	struct inotify_event_info *event;
74 	struct fsnotify_event *fsn_event;
75 	int ret;
76 	int len = 0;
77 	int alloc_len = sizeof(struct inotify_event_info);
78 
79 	BUG_ON(vfsmount_mark);
80 
81 	if ((inode_mark->mask & FS_EXCL_UNLINK) &&
82 	    (data_type == FSNOTIFY_EVENT_PATH)) {
83 		struct path *path = data;
84 
85 		if (d_unlinked(path->dentry))
86 			return 0;
87 	}
88 	if (file_name) {
89 		len = strlen(file_name);
90 		alloc_len += len + 1;
91 	}
92 
93 	pr_debug("%s: group=%p inode=%p mask=%x\n", __func__, group, inode,
94 		 mask);
95 
96 	i_mark = container_of(inode_mark, struct inotify_inode_mark,
97 			      fsn_mark);
98 
99 	event = kmalloc(alloc_len, GFP_KERNEL);
100 	if (unlikely(!event))
101 		return -ENOMEM;
102 
103 	fsn_event = &event->fse;
104 	fsnotify_init_event(fsn_event, inode, mask);
105 	event->wd = i_mark->wd;
106 	event->sync_cookie = cookie;
107 	event->name_len = len;
108 	if (len)
109 		strcpy(event->name, file_name);
110 
111 	ret = fsnotify_add_notify_event(group, fsn_event, inotify_merge);
112 	if (ret) {
113 		/* Our event wasn't used in the end. Free it. */
114 		fsnotify_destroy_event(group, fsn_event);
115 	}
116 
117 	if (inode_mark->mask & IN_ONESHOT)
118 		fsnotify_destroy_mark(inode_mark, group);
119 
120 	return 0;
121 }
122 
123 static void inotify_freeing_mark(struct fsnotify_mark *fsn_mark, struct fsnotify_group *group)
124 {
125 	inotify_ignored_and_remove_idr(fsn_mark, group);
126 }
127 
128 /*
129  * This is NEVER supposed to be called.  Inotify marks should either have been
130  * removed from the idr when the watch was removed or in the
131  * fsnotify_destroy_mark_by_group() call when the inotify instance was being
132  * torn down.  This is only called if the idr is about to be freed but there
133  * are still marks in it.
134  */
135 static int idr_callback(int id, void *p, void *data)
136 {
137 	struct fsnotify_mark *fsn_mark;
138 	struct inotify_inode_mark *i_mark;
139 	static bool warned = false;
140 
141 	if (warned)
142 		return 0;
143 
144 	warned = true;
145 	fsn_mark = p;
146 	i_mark = container_of(fsn_mark, struct inotify_inode_mark, fsn_mark);
147 
148 	WARN(1, "inotify closing but id=%d for fsn_mark=%p in group=%p still in "
149 		"idr.  Probably leaking memory\n", id, p, data);
150 
151 	/*
152 	 * I'm taking the liberty of assuming that the mark in question is a
153 	 * valid address and I'm dereferencing it.  This might help to figure
154 	 * out why we got here and the panic is no worse than the original
155 	 * BUG() that was here.
156 	 */
157 	if (fsn_mark)
158 		printk(KERN_WARNING "fsn_mark->group=%p inode=%p wd=%d\n",
159 			fsn_mark->group, fsn_mark->i.inode, i_mark->wd);
160 	return 0;
161 }
162 
163 static void inotify_free_group_priv(struct fsnotify_group *group)
164 {
165 	/* ideally the idr is empty and we won't hit the BUG in the callback */
166 	idr_for_each(&group->inotify_data.idr, idr_callback, group);
167 	idr_destroy(&group->inotify_data.idr);
168 	atomic_dec(&group->inotify_data.user->inotify_devs);
169 	free_uid(group->inotify_data.user);
170 }
171 
172 static void inotify_free_event(struct fsnotify_event *fsn_event)
173 {
174 	kfree(INOTIFY_E(fsn_event));
175 }
176 
177 const struct fsnotify_ops inotify_fsnotify_ops = {
178 	.handle_event = inotify_handle_event,
179 	.free_group_priv = inotify_free_group_priv,
180 	.free_event = inotify_free_event,
181 	.freeing_mark = inotify_freeing_mark,
182 };
183