fanotify: fix notification of groups with inode & mount marks

fsnotify() needs to merge inode and mount marks lists when notifying
groups about events so that ignore masks from inode marks are reflected
in mount mark notifications and groups are notified in proper order
(according to priorities).

Currently the sorting of the lists done by fsnotify_add_inode_mark() /
fsnotify_add_vfsmount_mark() and fsnotify() differed which resulted
ignore masks not being used in some cases.

Fix the problem by always using the same comparison function when
sorting / merging the mark lists.

Thanks to Heinrich Schuchardt for improvements of my patch.

Link: https://bugzilla.kernel.org/show_bug.cgi?id=87721
Signed-off-by: Jan Kara <jack@suse.cz>
Reported-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Tested-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 21 insertions, 15 deletions

diff --git a/fs/notify/fsnotify.c b/fs/notify/fsnotify.c
index 9d3e9c5..89326ac 100644
--- a/fs/notify/fsnotify.c
+++ b/fs/notify/fsnotify.c
@@ -229,8 +229,16 @@ int fsnotify(struct inode *to_tell, __u32 mask, void *data, int data_is,
 					      &fsnotify_mark_srcu);
 	}
 
+	/*
+	 * We need to merge inode & vfsmount mark lists so that inode mark
+	 * ignore masks are properly reflected for mount mark notifications.
+	 * That's why this traversal is so complicated...
+	 */
 	while (inode_node || vfsmount_node) {
-		inode_group = vfsmount_group = NULL;
+		inode_group = NULL;
+		inode_mark = NULL;
+		vfsmount_group = NULL;
+		vfsmount_mark = NULL;
 
 		if (inode_node) {
 			inode_mark = hlist_entry(srcu_dereference(inode_node, &fsnotify_mark_srcu),
@@ -244,21 +252,19 @@ int fsnotify(struct inode *to_tell, __u32 mask, void *data, int data_is,
 			vfsmount_group = vfsmount_mark->group;
 		}
 
-		if (inode_group > vfsmount_group) {
-			/* handle inode */
-			ret = send_to_group(to_tell, inode_mark, NULL, mask,
-					    data, data_is, cookie, file_name);
-			/* we didn't use the vfsmount_mark */
-			vfsmount_group = NULL;
-		} else if (vfsmount_group > inode_group) {
-			ret = send_to_group(to_tell, NULL, vfsmount_mark, mask,
-					    data, data_is, cookie, file_name);
-			inode_group = NULL;
-		} else {
-			ret = send_to_group(to_tell, inode_mark, vfsmount_mark,
-					    mask, data, data_is, cookie,
-					    file_name);
+		if (inode_group && vfsmount_group) {
+			int cmp = fsnotify_compare_groups(inode_group,
+							  vfsmount_group);
+			if (cmp > 0) {
+				inode_group = NULL;
+				inode_mark = NULL;
+			} else if (cmp < 0) {
+				vfsmount_group = NULL;
+				vfsmount_mark = NULL;
+			}
 		}
+		ret = send_to_group(to_tell, inode_mark, vfsmount_mark, mask,
+				    data, data_is, cookie, file_name);
 
 		if (ret && (mask & ALL_FSNOTIFY_PERM_EVENTS))
 			goto out;