fsnotify: fix ignore mask logic in fsnotify()

[ Upstream commit 9bdda4e9cf ]

Commit 92183a4289 ("fsnotify: fix ignore mask logic in
send_to_group()") acknoledges the use case of ignoring an event on
an inode mark, because of an ignore mask on a mount mark of the same
group (i.e. I want to get all events on this file, except for the events
that came from that mount).

This change depends on correctly merging the inode marks and mount marks
group lists, so that the mount mark ignore mask would be tested in
send_to_group(). Alas, the merging of the lists did not take into
account the case where event in question is not in the mask of any of
the mount marks.

To fix this, completely remove the tests for inode and mount event masks
from the lists merging code.

Fixes: 92183a4289 ("fsnotify: fix ignore mask logic in send_to_group")
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
[amir: backport to v4.14.y]
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

fs/notify/fsnotify.c

@@ -286,17 +286,13 @@ int fsnotify(struct inode *to_tell, __u32 mask, const void *data, int data_is,
 
 	iter_info.srcu_idx = srcu_read_lock(&fsnotify_mark_srcu);
 
-	if ((mask & FS_MODIFY) ||
-	    (test_mask & to_tell->i_fsnotify_mask)) {
-		inode_conn = srcu_dereference(to_tell->i_fsnotify_marks,
+	inode_conn = srcu_dereference(to_tell->i_fsnotify_marks,
+				      &fsnotify_mark_srcu);
+	if (inode_conn)
+		inode_node = srcu_dereference(inode_conn->list.first,
 					      &fsnotify_mark_srcu);
-		if (inode_conn)
-			inode_node = srcu_dereference(inode_conn->list.first,
-						      &fsnotify_mark_srcu);
-	}
 
-	if (mnt && ((mask & FS_MODIFY) ||
-		    (test_mask & mnt->mnt_fsnotify_mask))) {
+	if (mnt) {
 		inode_conn = srcu_dereference(to_tell->i_fsnotify_marks,
 					      &fsnotify_mark_srcu);
 		if (inode_conn)