linux-kernel - [PATCH 4.14 41/63] ext4: make sanity check in mballoc more strict

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Date:   Mon, 20 May 2019 14:14:20 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Jan Kara <jack@...e.cz>,
        Theodore Tso <tytso@....edu>, stable@...nel.org
Subject: [PATCH 4.14 41/63] ext4: make sanity check in mballoc more strict

From: Jan Kara <jack@...e.cz>

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@...e.cz>
Signed-off-by: Theodore Ts'o <tytso@....edu>
Cc: stable@...nel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

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

--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -1555,7 +1555,7 @@ static int mb_find_extent(struct ext4_bu
 		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 "