[PATCH v2 0/3] ext4: tighten mount-time superblock geometry validation

[Baokun Li <libaokun@linux.alibaba.com>]

Changes since v1:
 * Patch 1: Removed a spurious newline in the error message format string.
 * Added Patches 2 and 3 to fix additional issues reported by Sashiko
   (independent of Patch 1).

v1: https://patch.msgid.link/20260608061112.392391-1-libaokun@linux.alibaba.com

This series adds missing mount-time sanity checks for superblock
geometry parameters, preventing crafted filesystem images from causing
bitmap checksum corruption, integer overflow, or out-of-bounds inode
table access.

Patch 1 rejects filesystems where s_clusters_per_group or
s_inodes_per_group is not 8-aligned, since the bitmap checksum
functions operate on whole bytes and would leave trailing bits
unprotected.

Patch 2 reduces EXT4_MAX_CLUSTER_LOG_SIZE from 30 to 28 to match
the documented 256MB limit in mke2fs, preventing a 32-bit overflow
in the blocks-per-group consistency check on bigalloc filesystems.

Patch 3 rejects filesystems where s_inodes_per_group is not a
multiple of s_inodes_per_block, preventing truncation in the
s_itb_per_group calculation that could lead __ext4_get_inode_loc()
to read beyond the inode table.

Baokun Li (3):
  ext4: reject mount if clusters/inodes per group are not 8-aligned
  ext4: reduce max cluster size to match documented 256MB limit
  ext4: reject mount if inodes per group is not a multiple of inodes per
    block

 fs/ext4/ext4.h  |  2 +-
 fs/ext4/super.c | 11 +++++++----
 2 files changed, 8 insertions(+), 5 deletions(-)

-- 
2.43.7