ext4: avoid resizing to a partial cluster size

jira VULN-69318
cve CVE-2022-50020
commit-author Kiselev, Oleg <[email protected]>
commit 69cb8e9

This patch avoids an attempt to resize the filesystem to an
unaligned cluster boundary.  An online resize to a size that is not
integral to cluster size results in the last iteration attempting to
grow the fs by a negative amount, which trips a BUG_ON and leaves the fs
with a corrupted in-memory superblock.

	Signed-off-by: Oleg Kiselev <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
	Signed-off-by: Theodore Ts'o <[email protected]>
(cherry picked from commit 69cb8e9)
	Signed-off-by: Pratham Patel <[email protected]>

Author: thefossguy-ciq

fs/ext4/resize.c

@@ -1943,6 +1943,16 @@ int ext4_resize_fs(struct super_block *sb, ext4_fsblk_t n_blocks_count)
 	}
 	brelse(bh);
 
+	/*
+	 * For bigalloc, trim the requested size to the nearest cluster
+	 * boundary to avoid creating an unusable filesystem. We do this
+	 * silently, instead of returning an error, to avoid breaking
+	 * callers that blindly resize the filesystem to the full size of
+	 * the underlying block device.
+	 */
+	if (ext4_has_feature_bigalloc(sb))
+		n_blocks_count &= ~((1 << EXT4_CLUSTER_BITS(sb)) - 1);
+
 retry:
 	o_blocks_count = ext4_blocks_count(es);