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fanotify: introduce group flag FAN_REPORT_TARGET_FID

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FAN_REPORT_FID is ambiguous in that it reports the fid of the child for
some events and the fid of the parent for create/delete/move events.

The new FAN_REPORT_TARGET_FID flag is an implicit request to report
the fid of the target object of the operation (a.k.a the child inode)
also in create/delete/move events in addition to the fid of the parent
and the name of the child.

To reduce the test matrix for uninteresting use cases, the new
FAN_REPORT_TARGET_FID flag requires both FAN_REPORT_NAME and
FAN_REPORT_FID.  The convenience macro FAN_REPORT_DFID_NAME_TARGET
combines FAN_REPORT_TARGET_FID with all the required flags.

Link: https://lore.kernel.org/r/20211129201537.1932819-4-amir73il@gmail.com
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
This commit is contained in:
Amir Goldstein 2021-11-29 22:15:29 +02:00 committed by Jan Kara
parent 1c9007d62b
commit d61fd650e9
4 changed files with 51 additions and 14 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

48
fs/notify/fanotify/fanotify.c
View file

@ -458,17 +458,41 @@ static int fanotify_encode_fh(struct fanotify_fh *fh, struct inode *inode,
}
/*
* The inode to use as identifier when reporting fid depends on the event.
* Report the modified directory inode on dirent modification events.
* Report the "victim" inode otherwise.
* FAN_REPORT_FID is ambiguous in that it reports the fid of the child for
* some events and the fid of the parent for create/delete/move events.
*
* With the FAN_REPORT_TARGET_FID flag, the fid of the child is reported
* also in create/delete/move events in addition to the fid of the parent
* and the name of the child.
*/
static inline bool fanotify_report_child_fid(unsigned int fid_mode, u32 mask)
{
if (mask & ALL_FSNOTIFY_DIRENT_EVENTS)
return (fid_mode & FAN_REPORT_TARGET_FID);
return (fid_mode & FAN_REPORT_FID) && !(mask & FAN_ONDIR);
}
/*
* The inode to use as identifier when reporting fid depends on the event
* and the group flags.
*
* With the group flag FAN_REPORT_TARGET_FID, always report the child fid.
*
* Without the group flag FAN_REPORT_TARGET_FID, report the modified directory
* fid on dirent events and the child fid otherwise.
*
* For example:
* FS_ATTRIB reports the child inode even if reported on a watched parent.
* FS_CREATE reports the modified dir inode and not the created inode.
* FS_ATTRIB reports the child fid even if reported on a watched parent.
* FS_CREATE reports the modified dir fid without FAN_REPORT_TARGET_FID.
* and reports the created child fid with FAN_REPORT_TARGET_FID.
*/
static struct inode *fanotify_fid_inode(u32 event_mask, const void *data,
int data_type, struct inode *dir)
int data_type, struct inode *dir,
unsigned int fid_mode)
{
if (event_mask & ALL_FSNOTIFY_DIRENT_EVENTS)
if ((event_mask & ALL_FSNOTIFY_DIRENT_EVENTS) &&
!(fid_mode & FAN_REPORT_TARGET_FID))
return dir;
return fsnotify_data_inode(data, data_type);
@ -647,10 +671,11 @@ static struct fanotify_event *fanotify_alloc_event(struct fsnotify_group *group,
{
struct fanotify_event *event = NULL;
gfp_t gfp = GFP_KERNEL_ACCOUNT;
struct inode *id = fanotify_fid_inode(mask, data, data_type, dir);
unsigned int fid_mode = FAN_GROUP_FLAG(group, FANOTIFY_FID_BITS);
struct inode *id = fanotify_fid_inode(mask, data, data_type, dir,
fid_mode);
struct inode *dirid = fanotify_dfid_inode(mask, data, data_type, dir);
const struct path *path = fsnotify_data_path(data, data_type);
unsigned int fid_mode = FAN_GROUP_FLAG(group, FANOTIFY_FID_BITS);
struct mem_cgroup *old_memcg;
struct inode *child = NULL;
bool name_event = false;
@ -660,11 +685,10 @@ static struct fanotify_event *fanotify_alloc_event(struct fsnotify_group *group,
if ((fid_mode & FAN_REPORT_DIR_FID) && dirid) {
/*
* With both flags FAN_REPORT_DIR_FID and FAN_REPORT_FID, we
* report the child fid for events reported on a non-dir child
* For certain events and group flags, report the child fid
* in addition to reporting the parent fid and maybe child name.
*/
if ((fid_mode & FAN_REPORT_FID) && id != dirid && !ondir)
if (fanotify_report_child_fid(fid_mode, mask) && id != dirid)
child = id;
id = dirid;

11
fs/notify/fanotify/fanotify_user.c
View file

@ -1275,6 +1275,15 @@ SYSCALL_DEFINE2(fanotify_init, unsigned int, flags, unsigned int, event_f_flags)
if ((fid_mode & FAN_REPORT_NAME) && !(fid_mode & FAN_REPORT_DIR_FID))
return -EINVAL;
/*
* FAN_REPORT_TARGET_FID requires FAN_REPORT_NAME and FAN_REPORT_FID
* and is used as an indication to report both dir and child fid on all
* dirent events.
*/
if ((fid_mode & FAN_REPORT_TARGET_FID) &&
(!(fid_mode & FAN_REPORT_NAME) || !(fid_mode & FAN_REPORT_FID)))
return -EINVAL;
f_flags = O_RDWR | FMODE_NONOTIFY;
if (flags & FAN_CLOEXEC)
f_flags |= O_CLOEXEC;
@ -1667,7 +1676,7 @@ static int __init fanotify_user_setup(void)
FANOTIFY_DEFAULT_MAX_USER_MARKS);
BUILD_BUG_ON(FANOTIFY_INIT_FLAGS & FANOTIFY_INTERNAL_GROUP_FLAGS);
BUILD_BUG_ON(HWEIGHT32(FANOTIFY_INIT_FLAGS) != 11);
BUILD_BUG_ON(HWEIGHT32(FANOTIFY_INIT_FLAGS) != 12);
BUILD_BUG_ON(HWEIGHT32(FANOTIFY_MARK_FLAGS) != 9);
fanotify_mark_cache = KMEM_CACHE(fsnotify_mark,

2
include/linux/fanotify.h
View file

@ -25,7 +25,7 @@ extern struct ctl_table fanotify_table[]; /* for sysctl */
#define FANOTIFY_CLASS_BITS (FAN_CLASS_NOTIF | FANOTIFY_PERM_CLASSES)
#define FANOTIFY_FID_BITS (FAN_REPORT_FID | FAN_REPORT_DFID_NAME)
#define FANOTIFY_FID_BITS (FAN_REPORT_DFID_NAME_TARGET)
#define FANOTIFY_INFO_MODES (FANOTIFY_FID_BITS | FAN_REPORT_PIDFD)

4
include/uapi/linux/fanotify.h
View file

@ -57,9 +57,13 @@
#define FAN_REPORT_FID 0x00000200 /* Report unique file id */
#define FAN_REPORT_DIR_FID 0x00000400 /* Report unique directory id */
#define FAN_REPORT_NAME 0x00000800 /* Report events with name */
#define FAN_REPORT_TARGET_FID 0x00001000 /* Report dirent target id */
/* Convenience macro - FAN_REPORT_NAME requires FAN_REPORT_DIR_FID */
#define FAN_REPORT_DFID_NAME (FAN_REPORT_DIR_FID | FAN_REPORT_NAME)
/* Convenience macro - FAN_REPORT_TARGET_FID requires all other FID flags */
#define FAN_REPORT_DFID_NAME_TARGET (FAN_REPORT_DFID_NAME | \
FAN_REPORT_FID | FAN_REPORT_TARGET_FID)
/* Deprecated - do not use this in programs and do not add new flags here! */
#define FAN_ALL_INIT_FLAGS (FAN_CLOEXEC | FAN_NONBLOCK | \