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374ad001f7
The current codebase makes use of the zero-length array language
extension to the C90 standard, but the preferred mechanism to declare
variable-length types such as these ones is a flexible array member[1][2],
introduced in C99:
struct foo {
int stuff;
struct boo array[];
};
By making use of the mechanism above, we will get a compiler warning
in case the flexible array does not occur last in the structure, which
will help us prevent some kind of undefined behavior bugs from being
inadvertently introduced[3] to the codebase from now on.
Also, notice that, dynamic memory allocations won't be affected by
this change:
"Flexible array members have incomplete type, and so the sizeof operator
may not be applied. As a quirk of the original implementation of
zero-length arrays, sizeof evaluates to zero."[1]
sizeof(flexible-array-member) triggers a warning because flexible array
members have incomplete type[1]. There are some instances of code in
which the sizeof operator is being incorrectly/erroneously applied to
zero-length arrays and the result is zero. Such instances may be hiding
some bugs. So, this work (flexible-array member conversions) will also
help to get completely rid of those sorts of issues.
This issue was found with the help of Coccinelle.
[1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html
[2] https://github.com/KSPP/linux/issues/21
[3] commit 7649773293
("cxgb3/l2t: Fix undefined behaviour")
Link: https://lore.kernel.org/r/20200507185230.GA14229@embeddedor
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Signed-off-by: Jan Kara <jack@suse.cz>
211 lines
5.5 KiB
C
211 lines
5.5 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#include <linux/fsnotify_backend.h>
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#include <linux/path.h>
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#include <linux/slab.h>
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#include <linux/exportfs.h>
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extern struct kmem_cache *fanotify_mark_cache;
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extern struct kmem_cache *fanotify_fid_event_cachep;
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extern struct kmem_cache *fanotify_path_event_cachep;
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extern struct kmem_cache *fanotify_perm_event_cachep;
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/* Possible states of the permission event */
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enum {
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FAN_EVENT_INIT,
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FAN_EVENT_REPORTED,
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FAN_EVENT_ANSWERED,
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FAN_EVENT_CANCELED,
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};
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/*
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* 3 dwords are sufficient for most local fs (64bit ino, 32bit generation).
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* fh buf should be dword aligned. On 64bit arch, the ext_buf pointer is
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* stored in either the first or last 2 dwords.
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*/
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#define FANOTIFY_INLINE_FH_LEN (3 << 2)
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struct fanotify_fh {
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unsigned char buf[FANOTIFY_INLINE_FH_LEN];
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u8 type;
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u8 len;
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} __aligned(4);
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static inline bool fanotify_fh_has_ext_buf(struct fanotify_fh *fh)
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{
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return fh->len > FANOTIFY_INLINE_FH_LEN;
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}
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static inline char **fanotify_fh_ext_buf_ptr(struct fanotify_fh *fh)
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{
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BUILD_BUG_ON(__alignof__(char *) - 4 + sizeof(char *) >
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FANOTIFY_INLINE_FH_LEN);
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return (char **)ALIGN((unsigned long)(fh->buf), __alignof__(char *));
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}
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static inline void *fanotify_fh_ext_buf(struct fanotify_fh *fh)
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{
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return *fanotify_fh_ext_buf_ptr(fh);
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}
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static inline void *fanotify_fh_buf(struct fanotify_fh *fh)
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{
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return fanotify_fh_has_ext_buf(fh) ? fanotify_fh_ext_buf(fh) : fh->buf;
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}
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/*
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* Common structure for fanotify events. Concrete structs are allocated in
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* fanotify_handle_event() and freed when the information is retrieved by
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* userspace. The type of event determines how it was allocated, how it will
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* be freed and which concrete struct it may be cast to.
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*/
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enum fanotify_event_type {
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FANOTIFY_EVENT_TYPE_FID, /* fixed length */
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FANOTIFY_EVENT_TYPE_FID_NAME, /* variable length */
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FANOTIFY_EVENT_TYPE_PATH,
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FANOTIFY_EVENT_TYPE_PATH_PERM,
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};
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struct fanotify_event {
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struct fsnotify_event fse;
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u32 mask;
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enum fanotify_event_type type;
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struct pid *pid;
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};
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struct fanotify_fid_event {
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struct fanotify_event fae;
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__kernel_fsid_t fsid;
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struct fanotify_fh object_fh;
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};
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static inline struct fanotify_fid_event *
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FANOTIFY_FE(struct fanotify_event *event)
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{
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return container_of(event, struct fanotify_fid_event, fae);
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}
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struct fanotify_name_event {
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struct fanotify_event fae;
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__kernel_fsid_t fsid;
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struct fanotify_fh dir_fh;
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u8 name_len;
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char name[];
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};
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static inline struct fanotify_name_event *
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FANOTIFY_NE(struct fanotify_event *event)
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{
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return container_of(event, struct fanotify_name_event, fae);
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}
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static inline __kernel_fsid_t *fanotify_event_fsid(struct fanotify_event *event)
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{
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if (event->type == FANOTIFY_EVENT_TYPE_FID)
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return &FANOTIFY_FE(event)->fsid;
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else if (event->type == FANOTIFY_EVENT_TYPE_FID_NAME)
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return &FANOTIFY_NE(event)->fsid;
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else
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return NULL;
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}
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static inline struct fanotify_fh *fanotify_event_object_fh(
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struct fanotify_event *event)
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{
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if (event->type == FANOTIFY_EVENT_TYPE_FID)
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return &FANOTIFY_FE(event)->object_fh;
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else
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return NULL;
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}
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static inline struct fanotify_fh *fanotify_event_dir_fh(
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struct fanotify_event *event)
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{
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if (event->type == FANOTIFY_EVENT_TYPE_FID_NAME)
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return &FANOTIFY_NE(event)->dir_fh;
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else
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return NULL;
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}
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static inline int fanotify_event_object_fh_len(struct fanotify_event *event)
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{
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struct fanotify_fh *fh = fanotify_event_object_fh(event);
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return fh ? fh->len : 0;
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}
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static inline bool fanotify_event_has_name(struct fanotify_event *event)
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{
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return event->type == FANOTIFY_EVENT_TYPE_FID_NAME;
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}
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static inline int fanotify_event_name_len(struct fanotify_event *event)
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{
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return fanotify_event_has_name(event) ?
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FANOTIFY_NE(event)->name_len : 0;
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}
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struct fanotify_path_event {
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struct fanotify_event fae;
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struct path path;
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};
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static inline struct fanotify_path_event *
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FANOTIFY_PE(struct fanotify_event *event)
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{
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return container_of(event, struct fanotify_path_event, fae);
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}
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/*
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* Structure for permission fanotify events. It gets allocated and freed in
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* fanotify_handle_event() since we wait there for user response. When the
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* information is retrieved by userspace the structure is moved from
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* group->notification_list to group->fanotify_data.access_list to wait for
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* user response.
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*/
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struct fanotify_perm_event {
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struct fanotify_event fae;
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struct path path;
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unsigned short response; /* userspace answer to the event */
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unsigned short state; /* state of the event */
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int fd; /* fd we passed to userspace for this event */
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};
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static inline struct fanotify_perm_event *
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FANOTIFY_PERM(struct fanotify_event *event)
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{
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return container_of(event, struct fanotify_perm_event, fae);
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}
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static inline bool fanotify_is_perm_event(u32 mask)
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{
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return IS_ENABLED(CONFIG_FANOTIFY_ACCESS_PERMISSIONS) &&
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mask & FANOTIFY_PERM_EVENTS;
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}
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static inline struct fanotify_event *FANOTIFY_E(struct fsnotify_event *fse)
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{
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return container_of(fse, struct fanotify_event, fse);
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}
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static inline bool fanotify_event_has_path(struct fanotify_event *event)
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{
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return event->type == FANOTIFY_EVENT_TYPE_PATH ||
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event->type == FANOTIFY_EVENT_TYPE_PATH_PERM;
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}
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static inline struct path *fanotify_event_path(struct fanotify_event *event)
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{
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if (event->type == FANOTIFY_EVENT_TYPE_PATH)
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return &FANOTIFY_PE(event)->path;
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else if (event->type == FANOTIFY_EVENT_TYPE_PATH_PERM)
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return &FANOTIFY_PERM(event)->path;
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else
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return NULL;
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}
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struct fanotify_event *fanotify_alloc_event(struct fsnotify_group *group,
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struct inode *inode, u32 mask,
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const void *data, int data_type,
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const struct qstr *file_name,
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__kernel_fsid_t *fsid);
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