ocfs2: add extra consistency check to ocfs2_dx_dir_lookup_rec()

In 'ocfs2_dx_dir_lookup_rec()', check whether an extent list length of the
directory indexing block matches the one configured via the superblock
parameters established at mount, thus preventing an out-of-bounds accesses
while iterating over the extent records below.

Link: https://lkml.kernel.org/r/20251007094626.196143-1-dmantipov@yandex.ru
Reported-by: syzbot+30b53487d00b4f7f0922@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=30b53487d00b4f7f0922
Signed-off-by: Dmitry Antipov <dmantipov@yandex.ru>
Reviewed-by: Joseph Qi <joseph.qi@linux.alibaba.com>
Reviewed-by: Heming Zhao <heming.zhao@suse.com>>
Cc: Mark Fasheh <mark@fasheh.com>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Junxiao Bi <junxiao.bi@oracle.com>
Cc: Changwei Ge <gechangwei@live.cn>
Cc: Jun Piao <piaojun@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/fs/ocfs2/dir.c b/fs/ocfs2/dir.c
index 48b092bc83d4ba65474d8d1c93660cc38f70fca2..0fcaa0e907474b9a79933a3029b54783c39f3594 100644 (file)
--- a/fs/ocfs2/dir.c
+++ b/fs/ocfs2/dir.c
@@ -778,6 +778,14 @@ static int ocfs2_dx_dir_lookup_rec(struct inode *inode,
        struct ocfs2_extent_block *eb;
        struct ocfs2_extent_rec *rec = NULL;
 
+       if (le16_to_cpu(el->l_count) !=
+           ocfs2_extent_recs_per_dx_root(inode->i_sb)) {
+               ret = ocfs2_error(inode->i_sb,
+                                 "Inode %lu has invalid extent list length %u\n",
+                                 inode->i_ino, le16_to_cpu(el->l_count));
+               goto out;
+       }
+
        if (el->l_tree_depth) {
                ret = ocfs2_find_leaf(INODE_CACHE(inode), el, major_hash,
                                      &eb_bh);