fsnotify: fix ignore mask logic in send_to_group()

The ignore mask logic in send_to_group() does not match the logic
in fanotify_should_send_event(). In the latter, a vfsmount mark ignore
mask precedes an inode mark mask and in the former, it does not.

That difference may cause events to be sent to fanotify backend for no
reason. Fix the logic in send_to_group() to match that of
fanotify_should_send_event().

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>

fs/notify/fsnotify.c

@@ -192,8 +192,9 @@ static int send_to_group(struct inode *to_tell,
 			 struct fsnotify_iter_info *iter_info)
 {
 	struct fsnotify_group *group = NULL;
-	__u32 inode_test_mask = 0;
-	__u32 vfsmount_test_mask = 0;
+	__u32 test_mask = (mask & ~FS_EVENT_ON_CHILD);
+	__u32 marks_mask = 0;
+	__u32 marks_ignored_mask = 0;
 
 	if (unlikely(!inode_mark && !vfsmount_mark)) {
 		BUG();
@@ -213,29 +214,25 @@ static int send_to_group(struct inode *to_tell,
 	/* does the inode mark tell us to do something? */
 	if (inode_mark) {
 		group = inode_mark->group;
-		inode_test_mask = (mask & ~FS_EVENT_ON_CHILD);
-		inode_test_mask &= inode_mark->mask;
-		inode_test_mask &= ~inode_mark->ignored_mask;
+		marks_mask |= inode_mark->mask;
+		marks_ignored_mask |= inode_mark->ignored_mask;
 	}
 
 	/* does the vfsmount_mark tell us to do something? */
 	if (vfsmount_mark) {
-		vfsmount_test_mask = (mask & ~FS_EVENT_ON_CHILD);
 		group = vfsmount_mark->group;
-		vfsmount_test_mask &= vfsmount_mark->mask;
-		vfsmount_test_mask &= ~vfsmount_mark->ignored_mask;
-		if (inode_mark)
-			vfsmount_test_mask &= ~inode_mark->ignored_mask;
+		marks_mask |= vfsmount_mark->mask;
+		marks_ignored_mask |= vfsmount_mark->ignored_mask;
 	}
 
 	pr_debug("%s: group=%p to_tell=%p mask=%x inode_mark=%p"
-		 " inode_test_mask=%x vfsmount_mark=%p vfsmount_test_mask=%x"
+		 " vfsmount_mark=%p marks_mask=%x marks_ignored_mask=%x"
 		 " data=%p data_is=%d cookie=%d\n",
-		 __func__, group, to_tell, mask, inode_mark,
-		 inode_test_mask, vfsmount_mark, vfsmount_test_mask, data,
+		 __func__, group, to_tell, mask, inode_mark, vfsmount_mark,
+		 marks_mask, marks_ignored_mask, data,
 		 data_is, cookie);
 
-	if (!inode_test_mask && !vfsmount_test_mask)
+	if (!(test_mask & marks_mask & ~marks_ignored_mask))
 		return 0;
 
 	return group->ops->handle_event(group, to_tell, inode_mark,