Re: [ocfs2?] KASAN: use-after-free Read in __ocfs2_find_path

[Lizhi Xu]

Extent tree depth is never bigger than 256, because the high 8 bits cannot be used.

#syz test

diff --git a/fs/ocfs2/extent_map.c b/fs/ocfs2/extent_map.c
index f7672472fa82..2ca546af9191 100644
--- a/fs/ocfs2/extent_map.c
+++ b/fs/ocfs2/extent_map.c
@@ -415,6 +415,15 @@ static int ocfs2_get_clusters_nocache(struct inode *inode,
 	tree_height = le16_to_cpu(el->l_tree_depth);
 
 	if (tree_height > 0) {
+		if (tree_height > 256) {
+			ocfs2_error(inode->i_sb,
+				    "Inode %lu has too big tree depth %d in leaf block %llu\n",
+				    inode->i_ino,
+				    tree_height,
+				    (unsigned long long)di_bh->b_blocknr);
+			ret = -EROFS;
+			goto out;
+		}
 		ret = ocfs2_find_leaf(INODE_CACHE(inode), el, v_cluster,
 				      &eb_bh);
 		if (ret) {