xref: /openbmc/linux/fs/notify/fanotify/fanotify.h (revision dd21bfa4) 
1 /* SPDX-License-Identifier: GPL-2.0 */
2 #include <linux/fsnotify_backend.h>
3 #include <linux/path.h>
4 #include <linux/slab.h>
5 #include <linux/exportfs.h>
6 #include <linux/hashtable.h>
7 
8 extern struct kmem_cache *fanotify_mark_cache;
9 extern struct kmem_cache *fanotify_fid_event_cachep;
10 extern struct kmem_cache *fanotify_path_event_cachep;
11 extern struct kmem_cache *fanotify_perm_event_cachep;
12 
13 /* Possible states of the permission event */
14 enum {
15 	FAN_EVENT_INIT,
16 	FAN_EVENT_REPORTED,
17 	FAN_EVENT_ANSWERED,
18 	FAN_EVENT_CANCELED,
19 };
20 
21 /*
22  * 3 dwords are sufficient for most local fs (64bit ino, 32bit generation).
23  * fh buf should be dword aligned. On 64bit arch, the ext_buf pointer is
24  * stored in either the first or last 2 dwords.
25  */
26 #define FANOTIFY_INLINE_FH_LEN	(3 << 2)
27 #define FANOTIFY_FH_HDR_LEN	offsetof(struct fanotify_fh, buf)
28 
29 /* Fixed size struct for file handle */
30 struct fanotify_fh {
31 	u8 type;
32 	u8 len;
33 #define FANOTIFY_FH_FLAG_EXT_BUF 1
34 	u8 flags;
35 	u8 pad;
36 	unsigned char buf[];
37 } __aligned(4);
38 
39 /* Variable size struct for dir file handle + child file handle + name */
40 struct fanotify_info {
41 	/* size of dir_fh/file_fh including fanotify_fh hdr size */
42 	u8 dir_fh_totlen;
43 	u8 dir2_fh_totlen;
44 	u8 file_fh_totlen;
45 	u8 name_len;
46 	u8 name2_len;
47 	u8 pad[3];
48 	unsigned char buf[];
49 	/*
50 	 * (struct fanotify_fh) dir_fh starts at buf[0]
51 	 * (optional) dir2_fh starts at buf[dir_fh_totlen]
52 	 * (optional) file_fh starts at buf[dir_fh_totlen + dir2_fh_totlen]
53 	 * name starts at buf[dir_fh_totlen + dir2_fh_totlen + file_fh_totlen]
54 	 * ...
55 	 */
56 #define FANOTIFY_DIR_FH_SIZE(info)	((info)->dir_fh_totlen)
57 #define FANOTIFY_DIR2_FH_SIZE(info)	((info)->dir2_fh_totlen)
58 #define FANOTIFY_FILE_FH_SIZE(info)	((info)->file_fh_totlen)
59 #define FANOTIFY_NAME_SIZE(info)	((info)->name_len + 1)
60 #define FANOTIFY_NAME2_SIZE(info)	((info)->name2_len + 1)
61 
62 #define FANOTIFY_DIR_FH_OFFSET(info)	0
63 #define FANOTIFY_DIR2_FH_OFFSET(info) \
64 	(FANOTIFY_DIR_FH_OFFSET(info) + FANOTIFY_DIR_FH_SIZE(info))
65 #define FANOTIFY_FILE_FH_OFFSET(info) \
66 	(FANOTIFY_DIR2_FH_OFFSET(info) + FANOTIFY_DIR2_FH_SIZE(info))
67 #define FANOTIFY_NAME_OFFSET(info) \
68 	(FANOTIFY_FILE_FH_OFFSET(info) + FANOTIFY_FILE_FH_SIZE(info))
69 #define FANOTIFY_NAME2_OFFSET(info) \
70 	(FANOTIFY_NAME_OFFSET(info) + FANOTIFY_NAME_SIZE(info))
71 
72 #define FANOTIFY_DIR_FH_BUF(info) \
73 	((info)->buf + FANOTIFY_DIR_FH_OFFSET(info))
74 #define FANOTIFY_DIR2_FH_BUF(info) \
75 	((info)->buf + FANOTIFY_DIR2_FH_OFFSET(info))
76 #define FANOTIFY_FILE_FH_BUF(info) \
77 	((info)->buf + FANOTIFY_FILE_FH_OFFSET(info))
78 #define FANOTIFY_NAME_BUF(info) \
79 	((info)->buf + FANOTIFY_NAME_OFFSET(info))
80 #define FANOTIFY_NAME2_BUF(info) \
81 	((info)->buf + FANOTIFY_NAME2_OFFSET(info))
82 } __aligned(4);
83 
84 static inline bool fanotify_fh_has_ext_buf(struct fanotify_fh *fh)
85 {
86 	return (fh->flags & FANOTIFY_FH_FLAG_EXT_BUF);
87 }
88 
89 static inline char **fanotify_fh_ext_buf_ptr(struct fanotify_fh *fh)
90 {
91 	BUILD_BUG_ON(FANOTIFY_FH_HDR_LEN % 4);
92 	BUILD_BUG_ON(__alignof__(char *) - 4 + sizeof(char *) >
93 		     FANOTIFY_INLINE_FH_LEN);
94 	return (char **)ALIGN((unsigned long)(fh->buf), __alignof__(char *));
95 }
96 
97 static inline void *fanotify_fh_ext_buf(struct fanotify_fh *fh)
98 {
99 	return *fanotify_fh_ext_buf_ptr(fh);
100 }
101 
102 static inline void *fanotify_fh_buf(struct fanotify_fh *fh)
103 {
104 	return fanotify_fh_has_ext_buf(fh) ? fanotify_fh_ext_buf(fh) : fh->buf;
105 }
106 
107 static inline int fanotify_info_dir_fh_len(struct fanotify_info *info)
108 {
109 	if (!info->dir_fh_totlen ||
110 	    WARN_ON_ONCE(info->dir_fh_totlen < FANOTIFY_FH_HDR_LEN))
111 		return 0;
112 
113 	return info->dir_fh_totlen - FANOTIFY_FH_HDR_LEN;
114 }
115 
116 static inline struct fanotify_fh *fanotify_info_dir_fh(struct fanotify_info *info)
117 {
118 	BUILD_BUG_ON(offsetof(struct fanotify_info, buf) % 4);
119 
120 	return (struct fanotify_fh *)FANOTIFY_DIR_FH_BUF(info);
121 }
122 
123 static inline int fanotify_info_dir2_fh_len(struct fanotify_info *info)
124 {
125 	if (!info->dir2_fh_totlen ||
126 	    WARN_ON_ONCE(info->dir2_fh_totlen < FANOTIFY_FH_HDR_LEN))
127 		return 0;
128 
129 	return info->dir2_fh_totlen - FANOTIFY_FH_HDR_LEN;
130 }
131 
132 static inline struct fanotify_fh *fanotify_info_dir2_fh(struct fanotify_info *info)
133 {
134 	return (struct fanotify_fh *)FANOTIFY_DIR2_FH_BUF(info);
135 }
136 
137 static inline int fanotify_info_file_fh_len(struct fanotify_info *info)
138 {
139 	if (!info->file_fh_totlen ||
140 	    WARN_ON_ONCE(info->file_fh_totlen < FANOTIFY_FH_HDR_LEN))
141 		return 0;
142 
143 	return info->file_fh_totlen - FANOTIFY_FH_HDR_LEN;
144 }
145 
146 static inline struct fanotify_fh *fanotify_info_file_fh(struct fanotify_info *info)
147 {
148 	return (struct fanotify_fh *)FANOTIFY_FILE_FH_BUF(info);
149 }
150 
151 static inline char *fanotify_info_name(struct fanotify_info *info)
152 {
153 	if (!info->name_len)
154 		return NULL;
155 
156 	return FANOTIFY_NAME_BUF(info);
157 }
158 
159 static inline char *fanotify_info_name2(struct fanotify_info *info)
160 {
161 	if (!info->name2_len)
162 		return NULL;
163 
164 	return FANOTIFY_NAME2_BUF(info);
165 }
166 
167 static inline void fanotify_info_init(struct fanotify_info *info)
168 {
169 	BUILD_BUG_ON(FANOTIFY_FH_HDR_LEN + MAX_HANDLE_SZ > U8_MAX);
170 	BUILD_BUG_ON(NAME_MAX > U8_MAX);
171 
172 	info->dir_fh_totlen = 0;
173 	info->dir2_fh_totlen = 0;
174 	info->file_fh_totlen = 0;
175 	info->name_len = 0;
176 	info->name2_len = 0;
177 }
178 
179 /* These set/copy helpers MUST be called by order */
180 static inline void fanotify_info_set_dir_fh(struct fanotify_info *info,
181 					    unsigned int totlen)
182 {
183 	if (WARN_ON_ONCE(info->dir2_fh_totlen > 0) ||
184 	    WARN_ON_ONCE(info->file_fh_totlen > 0) ||
185 	    WARN_ON_ONCE(info->name_len > 0) ||
186 	    WARN_ON_ONCE(info->name2_len > 0))
187 		return;
188 
189 	info->dir_fh_totlen = totlen;
190 }
191 
192 static inline void fanotify_info_set_dir2_fh(struct fanotify_info *info,
193 					     unsigned int totlen)
194 {
195 	if (WARN_ON_ONCE(info->file_fh_totlen > 0) ||
196 	    WARN_ON_ONCE(info->name_len > 0) ||
197 	    WARN_ON_ONCE(info->name2_len > 0))
198 		return;
199 
200 	info->dir2_fh_totlen = totlen;
201 }
202 
203 static inline void fanotify_info_set_file_fh(struct fanotify_info *info,
204 					     unsigned int totlen)
205 {
206 	if (WARN_ON_ONCE(info->name_len > 0) ||
207 	    WARN_ON_ONCE(info->name2_len > 0))
208 		return;
209 
210 	info->file_fh_totlen = totlen;
211 }
212 
213 static inline void fanotify_info_copy_name(struct fanotify_info *info,
214 					   const struct qstr *name)
215 {
216 	if (WARN_ON_ONCE(name->len > NAME_MAX) ||
217 	    WARN_ON_ONCE(info->name2_len > 0))
218 		return;
219 
220 	info->name_len = name->len;
221 	strcpy(fanotify_info_name(info), name->name);
222 }
223 
224 static inline void fanotify_info_copy_name2(struct fanotify_info *info,
225 					    const struct qstr *name)
226 {
227 	if (WARN_ON_ONCE(name->len > NAME_MAX))
228 		return;
229 
230 	info->name2_len = name->len;
231 	strcpy(fanotify_info_name2(info), name->name);
232 }
233 
234 /*
235  * Common structure for fanotify events. Concrete structs are allocated in
236  * fanotify_handle_event() and freed when the information is retrieved by
237  * userspace. The type of event determines how it was allocated, how it will
238  * be freed and which concrete struct it may be cast to.
239  */
240 enum fanotify_event_type {
241 	FANOTIFY_EVENT_TYPE_FID, /* fixed length */
242 	FANOTIFY_EVENT_TYPE_FID_NAME, /* variable length */
243 	FANOTIFY_EVENT_TYPE_PATH,
244 	FANOTIFY_EVENT_TYPE_PATH_PERM,
245 	FANOTIFY_EVENT_TYPE_OVERFLOW, /* struct fanotify_event */
246 	FANOTIFY_EVENT_TYPE_FS_ERROR, /* struct fanotify_error_event */
247 	__FANOTIFY_EVENT_TYPE_NUM
248 };
249 
250 #define FANOTIFY_EVENT_TYPE_BITS \
251 	(ilog2(__FANOTIFY_EVENT_TYPE_NUM - 1) + 1)
252 #define FANOTIFY_EVENT_HASH_BITS \
253 	(32 - FANOTIFY_EVENT_TYPE_BITS)
254 
255 struct fanotify_event {
256 	struct fsnotify_event fse;
257 	struct hlist_node merge_list;	/* List for hashed merge */
258 	u32 mask;
259 	struct {
260 		unsigned int type : FANOTIFY_EVENT_TYPE_BITS;
261 		unsigned int hash : FANOTIFY_EVENT_HASH_BITS;
262 	};
263 	struct pid *pid;
264 };
265 
266 static inline void fanotify_init_event(struct fanotify_event *event,
267 				       unsigned int hash, u32 mask)
268 {
269 	fsnotify_init_event(&event->fse);
270 	INIT_HLIST_NODE(&event->merge_list);
271 	event->hash = hash;
272 	event->mask = mask;
273 	event->pid = NULL;
274 }
275 
276 #define FANOTIFY_INLINE_FH(name, size)					\
277 struct {								\
278 	struct fanotify_fh (name);					\
279 	/* Space for object_fh.buf[] - access with fanotify_fh_buf() */	\
280 	unsigned char _inline_fh_buf[(size)];				\
281 }
282 
283 struct fanotify_fid_event {
284 	struct fanotify_event fae;
285 	__kernel_fsid_t fsid;
286 
287 	FANOTIFY_INLINE_FH(object_fh, FANOTIFY_INLINE_FH_LEN);
288 };
289 
290 static inline struct fanotify_fid_event *
291 FANOTIFY_FE(struct fanotify_event *event)
292 {
293 	return container_of(event, struct fanotify_fid_event, fae);
294 }
295 
296 struct fanotify_name_event {
297 	struct fanotify_event fae;
298 	__kernel_fsid_t fsid;
299 	struct fanotify_info info;
300 };
301 
302 static inline struct fanotify_name_event *
303 FANOTIFY_NE(struct fanotify_event *event)
304 {
305 	return container_of(event, struct fanotify_name_event, fae);
306 }
307 
308 struct fanotify_error_event {
309 	struct fanotify_event fae;
310 	s32 error; /* Error reported by the Filesystem. */
311 	u32 err_count; /* Suppressed errors count */
312 
313 	__kernel_fsid_t fsid; /* FSID this error refers to. */
314 
315 	FANOTIFY_INLINE_FH(object_fh, MAX_HANDLE_SZ);
316 };
317 
318 static inline struct fanotify_error_event *
319 FANOTIFY_EE(struct fanotify_event *event)
320 {
321 	return container_of(event, struct fanotify_error_event, fae);
322 }
323 
324 static inline __kernel_fsid_t *fanotify_event_fsid(struct fanotify_event *event)
325 {
326 	if (event->type == FANOTIFY_EVENT_TYPE_FID)
327 		return &FANOTIFY_FE(event)->fsid;
328 	else if (event->type == FANOTIFY_EVENT_TYPE_FID_NAME)
329 		return &FANOTIFY_NE(event)->fsid;
330 	else if (event->type == FANOTIFY_EVENT_TYPE_FS_ERROR)
331 		return &FANOTIFY_EE(event)->fsid;
332 	else
333 		return NULL;
334 }
335 
336 static inline struct fanotify_fh *fanotify_event_object_fh(
337 						struct fanotify_event *event)
338 {
339 	if (event->type == FANOTIFY_EVENT_TYPE_FID)
340 		return &FANOTIFY_FE(event)->object_fh;
341 	else if (event->type == FANOTIFY_EVENT_TYPE_FID_NAME)
342 		return fanotify_info_file_fh(&FANOTIFY_NE(event)->info);
343 	else if (event->type == FANOTIFY_EVENT_TYPE_FS_ERROR)
344 		return &FANOTIFY_EE(event)->object_fh;
345 	else
346 		return NULL;
347 }
348 
349 static inline struct fanotify_info *fanotify_event_info(
350 						struct fanotify_event *event)
351 {
352 	if (event->type == FANOTIFY_EVENT_TYPE_FID_NAME)
353 		return &FANOTIFY_NE(event)->info;
354 	else
355 		return NULL;
356 }
357 
358 static inline int fanotify_event_object_fh_len(struct fanotify_event *event)
359 {
360 	struct fanotify_info *info = fanotify_event_info(event);
361 	struct fanotify_fh *fh = fanotify_event_object_fh(event);
362 
363 	if (info)
364 		return info->file_fh_totlen ? fh->len : 0;
365 	else
366 		return fh ? fh->len : 0;
367 }
368 
369 static inline int fanotify_event_dir_fh_len(struct fanotify_event *event)
370 {
371 	struct fanotify_info *info = fanotify_event_info(event);
372 
373 	return info ? fanotify_info_dir_fh_len(info) : 0;
374 }
375 
376 static inline int fanotify_event_dir2_fh_len(struct fanotify_event *event)
377 {
378 	struct fanotify_info *info = fanotify_event_info(event);
379 
380 	return info ? fanotify_info_dir2_fh_len(info) : 0;
381 }
382 
383 static inline bool fanotify_event_has_object_fh(struct fanotify_event *event)
384 {
385 	/* For error events, even zeroed fh are reported. */
386 	if (event->type == FANOTIFY_EVENT_TYPE_FS_ERROR)
387 		return true;
388 	return fanotify_event_object_fh_len(event) > 0;
389 }
390 
391 static inline bool fanotify_event_has_dir_fh(struct fanotify_event *event)
392 {
393 	return fanotify_event_dir_fh_len(event) > 0;
394 }
395 
396 static inline bool fanotify_event_has_dir2_fh(struct fanotify_event *event)
397 {
398 	return fanotify_event_dir2_fh_len(event) > 0;
399 }
400 
401 static inline bool fanotify_event_has_any_dir_fh(struct fanotify_event *event)
402 {
403 	return fanotify_event_has_dir_fh(event) ||
404 		fanotify_event_has_dir2_fh(event);
405 }
406 
407 struct fanotify_path_event {
408 	struct fanotify_event fae;
409 	struct path path;
410 };
411 
412 static inline struct fanotify_path_event *
413 FANOTIFY_PE(struct fanotify_event *event)
414 {
415 	return container_of(event, struct fanotify_path_event, fae);
416 }
417 
418 /*
419  * Structure for permission fanotify events. It gets allocated and freed in
420  * fanotify_handle_event() since we wait there for user response. When the
421  * information is retrieved by userspace the structure is moved from
422  * group->notification_list to group->fanotify_data.access_list to wait for
423  * user response.
424  */
425 struct fanotify_perm_event {
426 	struct fanotify_event fae;
427 	struct path path;
428 	unsigned short response;	/* userspace answer to the event */
429 	unsigned short state;		/* state of the event */
430 	int fd;		/* fd we passed to userspace for this event */
431 };
432 
433 static inline struct fanotify_perm_event *
434 FANOTIFY_PERM(struct fanotify_event *event)
435 {
436 	return container_of(event, struct fanotify_perm_event, fae);
437 }
438 
439 static inline bool fanotify_is_perm_event(u32 mask)
440 {
441 	return IS_ENABLED(CONFIG_FANOTIFY_ACCESS_PERMISSIONS) &&
442 		mask & FANOTIFY_PERM_EVENTS;
443 }
444 
445 static inline struct fanotify_event *FANOTIFY_E(struct fsnotify_event *fse)
446 {
447 	return container_of(fse, struct fanotify_event, fse);
448 }
449 
450 static inline bool fanotify_is_error_event(u32 mask)
451 {
452 	return mask & FAN_FS_ERROR;
453 }
454 
455 static inline bool fanotify_event_has_path(struct fanotify_event *event)
456 {
457 	return event->type == FANOTIFY_EVENT_TYPE_PATH ||
458 		event->type == FANOTIFY_EVENT_TYPE_PATH_PERM;
459 }
460 
461 static inline struct path *fanotify_event_path(struct fanotify_event *event)
462 {
463 	if (event->type == FANOTIFY_EVENT_TYPE_PATH)
464 		return &FANOTIFY_PE(event)->path;
465 	else if (event->type == FANOTIFY_EVENT_TYPE_PATH_PERM)
466 		return &FANOTIFY_PERM(event)->path;
467 	else
468 		return NULL;
469 }
470 
471 /*
472  * Use 128 size hash table to speed up events merge.
473  */
474 #define FANOTIFY_HTABLE_BITS	(7)
475 #define FANOTIFY_HTABLE_SIZE	(1 << FANOTIFY_HTABLE_BITS)
476 #define FANOTIFY_HTABLE_MASK	(FANOTIFY_HTABLE_SIZE - 1)
477 
478 /*
479  * Permission events and overflow event do not get merged - don't hash them.
480  */
481 static inline bool fanotify_is_hashed_event(u32 mask)
482 {
483 	return !(fanotify_is_perm_event(mask) ||
484 		 fsnotify_is_overflow_event(mask));
485 }
486 
487 static inline unsigned int fanotify_event_hash_bucket(
488 						struct fsnotify_group *group,
489 						struct fanotify_event *event)
490 {
491 	return event->hash & FANOTIFY_HTABLE_MASK;
492 }
493