Commit d61fd650 authored by Amir Goldstein's avatar Amir Goldstein Committed by Jan Kara
Browse files

fanotify: introduce group flag FAN_REPORT_TARGET_FID 

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: default avatarAmir Goldstein <amir73il@gmail.com>
Signed-off-by: default avatarJan Kara <jack@suse.cz>
parent 1c9007d6

fs/notify/fanotify/fanotify.c

+36 −12
Original line number Diff line number Diff line
@@ -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;

fs/notify/fanotify/fanotify_user.c

+10 −1
Original line number Diff line number Diff line
@@ -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,

include/linux/fanotify.h

+1 −1
Original line number Diff line number Diff line
@@ -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)

include/uapi/linux/fanotify.h

+4 −0
Original line number Diff line number Diff line
@@ -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 | \