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ext4: reject mount if clusters/inodes per group are not 8-aligned

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The block and inode bitmap checksums are computed over a whole number of
bytes: ext4_inode_bitmap_csum_*() use EXT4_INODES_PER_GROUP(sb) >> 3 and
ext4_block_bitmap_csum_*() use EXT4_CLUSTERS_PER_GROUP(sb) / 8 as the
length passed to ext4_chksum().

If s_inodes_per_group or s_clusters_per_group is not a multiple of 8, the
trailing fractional bits are excluded from the checksum.  Those bits are
then unprotected, and any incremental csum update path that assumes a
byte-aligned bitmap can compute a checksum inconsistent with the full
recalculation, corrupting the on-disk bitmap checksum.

Reject such filesystems at mount time by adding the missing " & 7"
alignment checks alongside the existing range validation.

Suggested-by: Theodore Ts'o <tytso@mit.edu>
Link: https://patch.msgid.link/h3n7jlfhyna64dn5o76qxcspnhxdddcs6crpxftmy7gnl7b3sx@jenszfpcsnit
Reported-by: Sashiko <sashiko-bot@kernel.org>
Closes: https://sashiko.dev/#/patchset/20260508121539.4174601-1-libaokun%40linux.alibaba.com?part=10
Signed-off-by: Baokun Li <libaokun@linux.alibaba.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Zhang Yi <yi.zhang@huawei.com>
Link: https://patch.msgid.link/20260608111150.827117-2-libaokun@linux.alibaba.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
This commit is contained in:
Baokun Li
2026-06-08 19:11:48 +08:00
committed by Theodore Ts'o
parent a13c140cc2
commit d42dc7726a
1 changed files with 6 additions and 4 deletions
Download Patch File Download Diff File Expand all files Collapse all files

10
fs/ext4/super.c
View File

@@ -4475,8 +4475,9 @@ static int ext4_handle_clustersize(struct super_block *sb)
sbi->s_cluster_bits = 0;
}
sbi->s_clusters_per_group = le32_to_cpu(es->s_clusters_per_group);
if (sbi->s_clusters_per_group > sb->s_blocksize * 8) {
ext4_msg(sb, KERN_ERR, "#clusters per group too big: %lu",
if (sbi->s_clusters_per_group > sb->s_blocksize * 8 ||
sbi->s_clusters_per_group & 7) {
ext4_msg(sb, KERN_ERR, "invalid #clusters per group: %lu",
sbi->s_clusters_per_group);
return -EINVAL;
}
@@ -5308,8 +5309,9 @@ static int ext4_block_group_meta_init(struct super_block *sb, int silent)
return -EINVAL;
}
if (sbi->s_inodes_per_group < sbi->s_inodes_per_block ||
sbi->s_inodes_per_group > sb->s_blocksize * 8) {
ext4_msg(sb, KERN_ERR, "invalid inodes per group: %lu\n",
sbi->s_inodes_per_group > sb->s_blocksize * 8 ||
sbi->s_inodes_per_group & 7) {
ext4_msg(sb, KERN_ERR, "invalid inodes per group: %lu",
sbi->s_inodes_per_group);
return -EINVAL;
}