ocfs2: validate directory-index entry counts when reading metadata

ocfs2_validate_dx_leaf() and ocfs2_validate_dx_root() check the ECC and
signature of an indexed-directory block before it reaches higher-level
callers, but neither validator bounds the ocfs2_dx_entry_list counts
against the capacity of the block that holds them.

ocfs2_dx_dir_search() then walks

	for (i = 0; i < le16_to_cpu(entry_list->de_num_used); i++)
		dx_entry = &entry_list->de_entries[i];

over de_num_used entries with no bounds check.  entry_list is either
dx_leaf->dl_list (from ocfs2_read_dx_leaf) or, for an inline root,
dx_root->dr_entries.  A crafted on-disk image can set de_num_used (and
de_count, which is the __counted_by_le() bound of de_entries) to 0xffff
and make the walk read far past the end of the 4KB metadata block, giving
a slab out-of-bounds read reachable from any path lookup, stat() or open()
on an indexed directory once the image is mounted.

Commit 775c17386a6f ("ocfs2: validate dx_root extent list fields during
block read") already bounds dr_list for the non-inline dx_root, but left
the inline dr_entries path and the dx_leaf dl_list unchecked.  Add the
same read-time validation for both entry lists: de_count must equal the
capacity of the block (ocfs2_dx_entries_per_leaf()/per_root()) and
de_num_used must not exceed de_count, rejecting corrupted metadata with
-EFSCORRUPTED before ocfs2_dx_dir_search() can walk an out-of-range entry
array.

de_count is always written as exactly the block capacity when a leaf or
inline root is formatted, so the equality check does not reject any valid
image.

Found by 0sec automated security-research tooling (https://0sec.ai).

Link: https://lore.kernel.org/20260713205625.92391-1-doruk@0sec.ai
Fixes: 9b7895efac90 ("ocfs2: Add a name indexed b-tree to directory inodes")
Fixes: 4ed8a6bb083b ("ocfs2: Store dir index records inline")
Assisted-by: 0sec:claude-opus-4-8
Signed-off-by: Doruk Tan Ozturk <doruk@0sec.ai>
Reviewed-by: Joseph Qi <joseph.qi@linux.alibaba.com>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Kees Cook <kees@kernel.org>
Cc: Mark Fasheh <mark@fasheh.com>
Cc: Junxiao Bi <junxiao.bi@oracle.com>
Cc: Changwei Ge <gechangwei@live.cn>
Cc: Jun Piao <piaojun@huawei.com>
Cc: Heming Zhao <heming.zhao@suse.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

0 files changed, 0 insertions, 0 deletions