xref: /openbmc/linux/fs/notify/fanotify/fanotify.h (revision d40d48e1) 
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 file_fh_totlen;
44 	u8 name_len;
45 	u8 pad;
46 	unsigned char buf[];
47 	/*
48 	 * (struct fanotify_fh) dir_fh starts at buf[0]
49 	 * (optional) file_fh starts at buf[dir_fh_totlen]
50 	 * name starts at buf[dir_fh_totlen + file_fh_totlen]
51 	 */
52 } __aligned(4);
53 
54 static inline bool fanotify_fh_has_ext_buf(struct fanotify_fh *fh)
55 {
56 	return (fh->flags & FANOTIFY_FH_FLAG_EXT_BUF);
57 }
58 
59 static inline char **fanotify_fh_ext_buf_ptr(struct fanotify_fh *fh)
60 {
61 	BUILD_BUG_ON(FANOTIFY_FH_HDR_LEN % 4);
62 	BUILD_BUG_ON(__alignof__(char *) - 4 + sizeof(char *) >
63 		     FANOTIFY_INLINE_FH_LEN);
64 	return (char **)ALIGN((unsigned long)(fh->buf), __alignof__(char *));
65 }
66 
67 static inline void *fanotify_fh_ext_buf(struct fanotify_fh *fh)
68 {
69 	return *fanotify_fh_ext_buf_ptr(fh);
70 }
71 
72 static inline void *fanotify_fh_buf(struct fanotify_fh *fh)
73 {
74 	return fanotify_fh_has_ext_buf(fh) ? fanotify_fh_ext_buf(fh) : fh->buf;
75 }
76 
77 static inline int fanotify_info_dir_fh_len(struct fanotify_info *info)
78 {
79 	if (!info->dir_fh_totlen ||
80 	    WARN_ON_ONCE(info->dir_fh_totlen < FANOTIFY_FH_HDR_LEN))
81 		return 0;
82 
83 	return info->dir_fh_totlen - FANOTIFY_FH_HDR_LEN;
84 }
85 
86 static inline struct fanotify_fh *fanotify_info_dir_fh(struct fanotify_info *info)
87 {
88 	BUILD_BUG_ON(offsetof(struct fanotify_info, buf) % 4);
89 
90 	return (struct fanotify_fh *)info->buf;
91 }
92 
93 static inline int fanotify_info_file_fh_len(struct fanotify_info *info)
94 {
95 	if (!info->file_fh_totlen ||
96 	    WARN_ON_ONCE(info->file_fh_totlen < FANOTIFY_FH_HDR_LEN))
97 		return 0;
98 
99 	return info->file_fh_totlen - FANOTIFY_FH_HDR_LEN;
100 }
101 
102 static inline struct fanotify_fh *fanotify_info_file_fh(struct fanotify_info *info)
103 {
104 	return (struct fanotify_fh *)(info->buf + info->dir_fh_totlen);
105 }
106 
107 static inline const char *fanotify_info_name(struct fanotify_info *info)
108 {
109 	return info->buf + info->dir_fh_totlen + info->file_fh_totlen;
110 }
111 
112 static inline void fanotify_info_init(struct fanotify_info *info)
113 {
114 	info->dir_fh_totlen = 0;
115 	info->file_fh_totlen = 0;
116 	info->name_len = 0;
117 }
118 
119 static inline unsigned int fanotify_info_len(struct fanotify_info *info)
120 {
121 	return info->dir_fh_totlen + info->file_fh_totlen + info->name_len;
122 }
123 
124 static inline void fanotify_info_copy_name(struct fanotify_info *info,
125 					   const struct qstr *name)
126 {
127 	info->name_len = name->len;
128 	strcpy(info->buf + info->dir_fh_totlen + info->file_fh_totlen,
129 	       name->name);
130 }
131 
132 /*
133  * Common structure for fanotify events. Concrete structs are allocated in
134  * fanotify_handle_event() and freed when the information is retrieved by
135  * userspace. The type of event determines how it was allocated, how it will
136  * be freed and which concrete struct it may be cast to.
137  */
138 enum fanotify_event_type {
139 	FANOTIFY_EVENT_TYPE_FID, /* fixed length */
140 	FANOTIFY_EVENT_TYPE_FID_NAME, /* variable length */
141 	FANOTIFY_EVENT_TYPE_PATH,
142 	FANOTIFY_EVENT_TYPE_PATH_PERM,
143 	FANOTIFY_EVENT_TYPE_OVERFLOW, /* struct fanotify_event */
144 	FANOTIFY_EVENT_TYPE_FS_ERROR, /* struct fanotify_error_event */
145 	__FANOTIFY_EVENT_TYPE_NUM
146 };
147 
148 #define FANOTIFY_EVENT_TYPE_BITS \
149 	(ilog2(__FANOTIFY_EVENT_TYPE_NUM - 1) + 1)
150 #define FANOTIFY_EVENT_HASH_BITS \
151 	(32 - FANOTIFY_EVENT_TYPE_BITS)
152 
153 struct fanotify_event {
154 	struct fsnotify_event fse;
155 	struct hlist_node merge_list;	/* List for hashed merge */
156 	u32 mask;
157 	struct {
158 		unsigned int type : FANOTIFY_EVENT_TYPE_BITS;
159 		unsigned int hash : FANOTIFY_EVENT_HASH_BITS;
160 	};
161 	struct pid *pid;
162 };
163 
164 static inline void fanotify_init_event(struct fanotify_event *event,
165 				       unsigned int hash, u32 mask)
166 {
167 	fsnotify_init_event(&event->fse);
168 	INIT_HLIST_NODE(&event->merge_list);
169 	event->hash = hash;
170 	event->mask = mask;
171 	event->pid = NULL;
172 }
173 
174 #define FANOTIFY_INLINE_FH(name, size)					\
175 struct {								\
176 	struct fanotify_fh (name);					\
177 	/* Space for object_fh.buf[] - access with fanotify_fh_buf() */	\
178 	unsigned char _inline_fh_buf[(size)];				\
179 }
180 
181 struct fanotify_fid_event {
182 	struct fanotify_event fae;
183 	__kernel_fsid_t fsid;
184 
185 	FANOTIFY_INLINE_FH(object_fh, FANOTIFY_INLINE_FH_LEN);
186 };
187 
188 static inline struct fanotify_fid_event *
189 FANOTIFY_FE(struct fanotify_event *event)
190 {
191 	return container_of(event, struct fanotify_fid_event, fae);
192 }
193 
194 struct fanotify_name_event {
195 	struct fanotify_event fae;
196 	__kernel_fsid_t fsid;
197 	struct fanotify_info info;
198 };
199 
200 static inline struct fanotify_name_event *
201 FANOTIFY_NE(struct fanotify_event *event)
202 {
203 	return container_of(event, struct fanotify_name_event, fae);
204 }
205 
206 struct fanotify_error_event {
207 	struct fanotify_event fae;
208 	s32 error; /* Error reported by the Filesystem. */
209 	u32 err_count; /* Suppressed errors count */
210 
211 	__kernel_fsid_t fsid; /* FSID this error refers to. */
212 
213 	FANOTIFY_INLINE_FH(object_fh, MAX_HANDLE_SZ);
214 };
215 
216 static inline struct fanotify_error_event *
217 FANOTIFY_EE(struct fanotify_event *event)
218 {
219 	return container_of(event, struct fanotify_error_event, fae);
220 }
221 
222 static inline __kernel_fsid_t *fanotify_event_fsid(struct fanotify_event *event)
223 {
224 	if (event->type == FANOTIFY_EVENT_TYPE_FID)
225 		return &FANOTIFY_FE(event)->fsid;
226 	else if (event->type == FANOTIFY_EVENT_TYPE_FID_NAME)
227 		return &FANOTIFY_NE(event)->fsid;
228 	else if (event->type == FANOTIFY_EVENT_TYPE_FS_ERROR)
229 		return &FANOTIFY_EE(event)->fsid;
230 	else
231 		return NULL;
232 }
233 
234 static inline struct fanotify_fh *fanotify_event_object_fh(
235 						struct fanotify_event *event)
236 {
237 	if (event->type == FANOTIFY_EVENT_TYPE_FID)
238 		return &FANOTIFY_FE(event)->object_fh;
239 	else if (event->type == FANOTIFY_EVENT_TYPE_FID_NAME)
240 		return fanotify_info_file_fh(&FANOTIFY_NE(event)->info);
241 	else if (event->type == FANOTIFY_EVENT_TYPE_FS_ERROR)
242 		return &FANOTIFY_EE(event)->object_fh;
243 	else
244 		return NULL;
245 }
246 
247 static inline struct fanotify_info *fanotify_event_info(
248 						struct fanotify_event *event)
249 {
250 	if (event->type == FANOTIFY_EVENT_TYPE_FID_NAME)
251 		return &FANOTIFY_NE(event)->info;
252 	else
253 		return NULL;
254 }
255 
256 static inline int fanotify_event_object_fh_len(struct fanotify_event *event)
257 {
258 	struct fanotify_info *info = fanotify_event_info(event);
259 	struct fanotify_fh *fh = fanotify_event_object_fh(event);
260 
261 	if (info)
262 		return info->file_fh_totlen ? fh->len : 0;
263 	else
264 		return fh ? fh->len : 0;
265 }
266 
267 static inline int fanotify_event_dir_fh_len(struct fanotify_event *event)
268 {
269 	struct fanotify_info *info = fanotify_event_info(event);
270 
271 	return info ? fanotify_info_dir_fh_len(info) : 0;
272 }
273 
274 static inline bool fanotify_event_has_object_fh(struct fanotify_event *event)
275 {
276 	/* For error events, even zeroed fh are reported. */
277 	if (event->type == FANOTIFY_EVENT_TYPE_FS_ERROR)
278 		return true;
279 	return fanotify_event_object_fh_len(event) > 0;
280 }
281 
282 static inline bool fanotify_event_has_dir_fh(struct fanotify_event *event)
283 {
284 	return fanotify_event_dir_fh_len(event) > 0;
285 }
286 
287 struct fanotify_path_event {
288 	struct fanotify_event fae;
289 	struct path path;
290 };
291 
292 static inline struct fanotify_path_event *
293 FANOTIFY_PE(struct fanotify_event *event)
294 {
295 	return container_of(event, struct fanotify_path_event, fae);
296 }
297 
298 /*
299  * Structure for permission fanotify events. It gets allocated and freed in
300  * fanotify_handle_event() since we wait there for user response. When the
301  * information is retrieved by userspace the structure is moved from
302  * group->notification_list to group->fanotify_data.access_list to wait for
303  * user response.
304  */
305 struct fanotify_perm_event {
306 	struct fanotify_event fae;
307 	struct path path;
308 	unsigned short response;	/* userspace answer to the event */
309 	unsigned short state;		/* state of the event */
310 	int fd;		/* fd we passed to userspace for this event */
311 };
312 
313 static inline struct fanotify_perm_event *
314 FANOTIFY_PERM(struct fanotify_event *event)
315 {
316 	return container_of(event, struct fanotify_perm_event, fae);
317 }
318 
319 static inline bool fanotify_is_perm_event(u32 mask)
320 {
321 	return IS_ENABLED(CONFIG_FANOTIFY_ACCESS_PERMISSIONS) &&
322 		mask & FANOTIFY_PERM_EVENTS;
323 }
324 
325 static inline struct fanotify_event *FANOTIFY_E(struct fsnotify_event *fse)
326 {
327 	return container_of(fse, struct fanotify_event, fse);
328 }
329 
330 static inline bool fanotify_is_error_event(u32 mask)
331 {
332 	return mask & FAN_FS_ERROR;
333 }
334 
335 static inline bool fanotify_event_has_path(struct fanotify_event *event)
336 {
337 	return event->type == FANOTIFY_EVENT_TYPE_PATH ||
338 		event->type == FANOTIFY_EVENT_TYPE_PATH_PERM;
339 }
340 
341 static inline struct path *fanotify_event_path(struct fanotify_event *event)
342 {
343 	if (event->type == FANOTIFY_EVENT_TYPE_PATH)
344 		return &FANOTIFY_PE(event)->path;
345 	else if (event->type == FANOTIFY_EVENT_TYPE_PATH_PERM)
346 		return &FANOTIFY_PERM(event)->path;
347 	else
348 		return NULL;
349 }
350 
351 /*
352  * Use 128 size hash table to speed up events merge.
353  */
354 #define FANOTIFY_HTABLE_BITS	(7)
355 #define FANOTIFY_HTABLE_SIZE	(1 << FANOTIFY_HTABLE_BITS)
356 #define FANOTIFY_HTABLE_MASK	(FANOTIFY_HTABLE_SIZE - 1)
357 
358 /*
359  * Permission events and overflow event do not get merged - don't hash them.
360  */
361 static inline bool fanotify_is_hashed_event(u32 mask)
362 {
363 	return !(fanotify_is_perm_event(mask) ||
364 		 fsnotify_is_overflow_event(mask));
365 }
366 
367 static inline unsigned int fanotify_event_hash_bucket(
368 						struct fsnotify_group *group,
369 						struct fanotify_event *event)
370 {
371 	return event->hash & FANOTIFY_HTABLE_MASK;
372 }
373