ext4: make sanity check in mballoc more strict

commit 31562b954b60f02acb91b7349dc6432d3f8c3c5f upstream.

The sanity check in mb_find_extent() only checked that returned extent
does not extend past blocksize * 8, however it should not extend past
EXT4_CLUSTERS_PER_GROUP(sb). This can happen when clusters_per_group <
blocksize * 8 and the tail of the bitmap is not properly filled by 1s
which happened e.g. when ancient kernels have grown the filesystem.

Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index e29fce2..cc229f3 100644 (file)
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -1539,7 +1539,7 @@ static int mb_find_extent(struct ext4_buddy *e4b, int block,
                ex->fe_len += 1 << order;
        }
 
-       if (ex->fe_start + ex->fe_len > (1 << (e4b->bd_blkbits + 3))) {
+       if (ex->fe_start + ex->fe_len > EXT4_CLUSTERS_PER_GROUP(e4b->bd_sb)) {
                /* Should never happen! (but apparently sometimes does?!?) */
                WARN_ON(1);
                ext4_error(e4b->bd_sb, "corruption or bug in mb_find_extent "