summaryrefslogtreecommitdiffstats
path: root/fs/notify/fanotify/fanotify.h
blob: 4a5e555dc3d25d4f33104f35c9750409e4225713 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
/* SPDX-License-Identifier: GPL-2.0 */
#include <linux/fsnotify_backend.h>
#include <linux/path.h>
#include <linux/slab.h>
#include <linux/exportfs.h>
#include <linux/hashtable.h>

extern struct kmem_cache *fanotify_mark_cache;
extern struct kmem_cache *fanotify_fid_event_cachep;
extern struct kmem_cache *fanotify_path_event_cachep;
extern struct kmem_cache *fanotify_perm_event_cachep;

/* Possible states of the permission event */
enum {
	FAN_EVENT_INIT,
	FAN_EVENT_REPORTED,
	FAN_EVENT_ANSWERED,
	FAN_EVENT_CANCELED,
};

/*
 * 3 dwords are sufficient for most local fs (64bit ino, 32bit generation).
 * fh buf should be dword aligned. On 64bit arch, the ext_buf pointer is
 * stored in either the first or last 2 dwords.
 */
#define FANOTIFY_INLINE_FH_LEN	(3 << 2)
#define FANOTIFY_FH_HDR_LEN	offsetof(struct fanotify_fh, buf)

/* Fixed size struct for file handle */
struct fanotify_fh {
	u8 type;
	u8 len;
#define FANOTIFY_FH_FLAG_EXT_BUF 1
	u8 flags;
	u8 pad;
	unsigned char buf[];
} __aligned(4);

/* Variable size struct for dir file handle + child file handle + name */
struct fanotify_info {
	/* size of dir_fh/file_fh including fanotify_fh hdr size */
	u8 dir_fh_totlen;
	u8 file_fh_totlen;
	u8 name_len;
	u8 pad;
	unsigned char buf[];
	/*
	 * (struct fanotify_fh) dir_fh starts at buf[0]
	 * (optional) file_fh starts at buf[dir_fh_totlen]
	 * name starts at buf[dir_fh_totlen + file_fh_totlen]
	 */
} __aligned(4);

static inline bool fanotify_fh_has_ext_buf(struct fanotify_fh *fh)
{
	return (fh->flags & FANOTIFY_FH_FLAG_EXT_BUF);
}

static inline char **fanotify_fh_ext_buf_ptr(struct fanotify_fh *fh)
{
	BUILD_BUG_ON(FANOTIFY_FH_HDR_LEN % 4);
	BUILD_BUG_ON(__alignof__(char *) - 4 + sizeof(char *) >
		     FANOTIFY_INLINE_FH_LEN);
	return (char **)ALIGN((unsigned long)(fh->buf), __alignof__(char *));
}

static inline void *fanotify_fh_ext_buf(struct fanotify_fh *fh)
{
	return *fanotify_fh_ext_buf_ptr(fh);
}

static inline void *fanotify_fh_buf(struct fanotify_fh *fh)
{
	return fanotify_fh_has_ext_buf(fh) ? fanotify_fh_ext_buf(fh) : fh->buf;
}

static inline int fanotify_info_dir_fh_len(struct fanotify_info *info)
{
	if (!info->dir_fh_totlen ||
	    WARN_ON_ONCE(info->dir_fh_totlen < FANOTIFY_FH_HDR_LEN))
		return 0;

	return info->dir_fh_totlen - FANOTIFY_FH_HDR_LEN;
}

static inline struct fanotify_fh *fanotify_info_dir_fh(struct fanotify_info *info)
{
	BUILD_BUG_ON(offsetof(struct fanotify_info, buf) % 4);

	return (struct fanotify_fh *)info->buf;
}

static inline int fanotify_info_file_fh_len(struct fanotify_info *info)
{
	if (!info->file_fh_totlen ||
	    WARN_ON_ONCE(info->file_fh_totlen < FANOTIFY_FH_HDR_LEN))
		return 0;

	return info->file_fh_totlen - FANOTIFY_FH_HDR_LEN;
}

static inline struct fanotify_fh *fanotify_info_file_fh(struct fanotify_info *info)
{
	return (struct fanotify_fh *)(info->buf + info->dir_fh_totlen);
}

static inline const char *fanotify_info_name(struct fanotify_info *info)
{
	return info->buf + info->dir_fh_totlen + info->file_fh_totlen;
}

static inline void fanotify_info_init(struct fanotify_info *info)
{
	info->dir_fh_totlen = 0;
	info->file_fh_totlen = 0;
	info->name_len = 0;
}

static inline unsigned int fanotify_info_len(struct fanotify_info *info)
{
	return info->dir_fh_totlen + info->file_fh_totlen + info->name_len;
}

static inline void fanotify_info_copy_name(struct fanotify_info *info,
					   const struct qstr *name)
{
	info->name_len = name->len;
	strcpy(info->buf + info->dir_fh_totlen + info->file_fh_totlen,
	       name->name);
}

/*
 * Common structure for fanotify events. Concrete structs are allocated in
 * fanotify_handle_event() and freed when the information is retrieved by
 * userspace. The type of event determines how it was allocated, how it will
 * be freed and which concrete struct it may be cast to.
 */
enum fanotify_event_type {
	FANOTIFY_EVENT_TYPE_FID, /* fixed length */
	FANOTIFY_EVENT_TYPE_FID_NAME, /* variable length */
	FANOTIFY_EVENT_TYPE_PATH,
	FANOTIFY_EVENT_TYPE_PATH_PERM,
	FANOTIFY_EVENT_TYPE_OVERFLOW, /* struct fanotify_event */
	__FANOTIFY_EVENT_TYPE_NUM
};

#define FANOTIFY_EVENT_TYPE_BITS \
	(ilog2(__FANOTIFY_EVENT_TYPE_NUM - 1) + 1)
#define FANOTIFY_EVENT_HASH_BITS \
	(32 - FANOTIFY_EVENT_TYPE_BITS)

struct fanotify_event {
	struct fsnotify_event fse;
	struct hlist_node merge_list;	/* List for hashed merge */
	u32 mask;
	struct {
		unsigned int type : FANOTIFY_EVENT_TYPE_BITS;
		unsigned int hash : FANOTIFY_EVENT_HASH_BITS;
	};
	struct pid *pid;
};

static inline void fanotify_init_event(struct fanotify_event *event,
				       unsigned int hash, u32 mask)
{
	fsnotify_init_event(&event->fse);
	INIT_HLIST_NODE(&event->merge_list);
	event->hash = hash;
	event->mask = mask;
	event->pid = NULL;
}

struct fanotify_fid_event {
	struct fanotify_event fae;
	__kernel_fsid_t fsid;
	struct fanotify_fh object_fh;
	/* Reserve space in object_fh.buf[] - access with fanotify_fh_buf() */
	unsigned char _inline_fh_buf[FANOTIFY_INLINE_FH_LEN];
};

static inline struct fanotify_fid_event *
FANOTIFY_FE(struct fanotify_event *event)
{
	return container_of(event, struct fanotify_fid_event, fae);
}

struct fanotify_name_event {
	struct fanotify_event fae;
	__kernel_fsid_t fsid;
	struct fanotify_info info;
};

static inline struct fanotify_name_event *
FANOTIFY_NE(struct fanotify_event *event)
{
	return container_of(event, struct fanotify_name_event, fae);
}

static inline __kernel_fsid_t *fanotify_event_fsid(struct fanotify_event *event)
{
	if (event->type == FANOTIFY_EVENT_TYPE_FID)
		return &FANOTIFY_FE(event)->fsid;
	else if (event->type == FANOTIFY_EVENT_TYPE_FID_NAME)
		return &FANOTIFY_NE(event)->fsid;
	else
		return NULL;
}

static inline struct fanotify_fh *fanotify_event_object_fh(
						struct fanotify_event *event)
{
	if (event->type == FANOTIFY_EVENT_TYPE_FID)
		return &FANOTIFY_FE(event)->object_fh;
	else if (event->type == FANOTIFY_EVENT_TYPE_FID_NAME)
		return fanotify_info_file_fh(&FANOTIFY_NE(event)->info);
	else
		return NULL;
}

static inline struct fanotify_info *fanotify_event_info(
						struct fanotify_event *event)
{
	if (event->type == FANOTIFY_EVENT_TYPE_FID_NAME)
		return &FANOTIFY_NE(event)->info;
	else
		return NULL;
}

static inline int fanotify_event_object_fh_len(struct fanotify_event *event)
{
	struct fanotify_info *info = fanotify_event_info(event);
	struct fanotify_fh *fh = fanotify_event_object_fh(event);

	if (info)
		return info->file_fh_totlen ? fh->len : 0;
	else
		return fh ? fh->len : 0;
}

static inline int fanotify_event_dir_fh_len(struct fanotify_event *event)
{
	struct fanotify_info *info = fanotify_event_info(event);

	return info ? fanotify_info_dir_fh_len(info) : 0;
}

struct fanotify_path_event {
	struct fanotify_event fae;
	struct path path;
};

static inline struct fanotify_path_event *
FANOTIFY_PE(struct fanotify_event *event)
{
	return container_of(event, struct fanotify_path_event, fae);
}

/*
 * Structure for permission fanotify events. It gets allocated and freed in
 * fanotify_handle_event() since we wait there for user response. When the
 * information is retrieved by userspace the structure is moved from
 * group->notification_list to group->fanotify_data.access_list to wait for
 * user response.
 */
struct fanotify_perm_event {
	struct fanotify_event fae;
	struct path path;
	unsigned short response;	/* userspace answer to the event */
	unsigned short state;		/* state of the event */
	int fd;		/* fd we passed to userspace for this event */
};

static inline struct fanotify_perm_event *
FANOTIFY_PERM(struct fanotify_event *event)
{
	return container_of(event, struct fanotify_perm_event, fae);
}

static inline bool fanotify_is_perm_event(u32 mask)
{
	return IS_ENABLED(CONFIG_FANOTIFY_ACCESS_PERMISSIONS) &&
		mask & FANOTIFY_PERM_EVENTS;
}

static inline struct fanotify_event *FANOTIFY_E(struct fsnotify_event *fse)
{
	return container_of(fse, struct fanotify_event, fse);
}

static inline bool fanotify_event_has_path(struct fanotify_event *event)
{
	return event->type == FANOTIFY_EVENT_TYPE_PATH ||
		event->type == FANOTIFY_EVENT_TYPE_PATH_PERM;
}

static inline struct path *fanotify_event_path(struct fanotify_event *event)
{
	if (event->type == FANOTIFY_EVENT_TYPE_PATH)
		return &FANOTIFY_PE(event)->path;
	else if (event->type == FANOTIFY_EVENT_TYPE_PATH_PERM)
		return &FANOTIFY_PERM(event)->path;
	else
		return NULL;
}

/*
 * Use 128 size hash table to speed up events merge.
 */
#define FANOTIFY_HTABLE_BITS	(7)
#define FANOTIFY_HTABLE_SIZE	(1 << FANOTIFY_HTABLE_BITS)
#define FANOTIFY_HTABLE_MASK	(FANOTIFY_HTABLE_SIZE - 1)

/*
 * Permission events and overflow event do not get merged - don't hash them.
 */
static inline bool fanotify_is_hashed_event(u32 mask)
{
	return !fanotify_is_perm_event(mask) && !(mask & FS_Q_OVERFLOW);
}

static inline unsigned int fanotify_event_hash_bucket(
						struct fsnotify_group *group,
						struct fanotify_event *event)
{
	return event->hash & FANOTIFY_HTABLE_MASK;
}