From 31562b954b60f02acb91b7349dc6432d3f8c3c5f Mon Sep 17 00:00:00 2001
From: Jan Kara <jack@suse.cz>
Date: Sat, 6 Apr 2019 18:33:06 -0400
Subject: [PATCH] ext4: make sanity check in mballoc more strict
Git-commit: 31562b954b60f02acb91b7349dc6432d3f8c3c5f
Patch-mainline: v5.2-rc1
References: bsc#1136439

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
Acked-by: Jan Kara <jack@suse.cz>

---
 fs/ext4/mballoc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index 6fb76d408093..8ef5f12bbee2 100644
--- 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 "
-- 
2.16.4