ext4: reject mount if inodes per group is not a multiple of inodes per block

If s_inodes_per_group is not a multiple of s_inodes_per_block, the
division that computes s_itb_per_group truncates, reserving fewer blocks
for the inode table than needed.

On a crafted filesystem image, this allows __ext4_get_inode_loc() to
compute a block offset beyond the inode table, reading unrelated data as
an inode structure.

Add the missing divisibility check alongside the existing validation in
ext4_block_group_meta_init().

Reported-by: Sashiko <sashiko-bot@kernel.org>
Closes: https://sashiko.dev/#/patchset/20260608061112.392391-1-libaokun%40linux.alibaba.com
Signed-off-by: Baokun Li <libaokun@linux.alibaba.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Zhang Yi <yi.zhang@huawei.com>
Reviewed-by: Andreas Dilger <adilger@dilger.ca>
Link: https://patch.msgid.link/20260608111150.827117-4-libaokun@linux.alibaba.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

0 files changed, 0 insertions, 0 deletions