From: Pan Bian <bianpan2016@163.com>
Date: Sun, 25 Nov 2018 00:58:02 +0000 (+0800)
Subject: ext2: fix potential use after free
X-Git-Url: http://git.cdn.openwrt.org/?a=commitdiff_plain;h=ecebf55d27a11538ea84aee0be643dd953f830d5;p=openwrt%2Fstaging%2Fblogic.git

ext2: fix potential use after free

The function ext2_xattr_set calls brelse(bh) to drop the reference count
of bh. After that, bh may be freed. However, following brelse(bh),
it reads bh->b_data via macro HDR(bh). This may result in a
use-after-free bug. This patch moves brelse(bh) after reading field.

CC: stable@vger.kernel.org
Signed-off-by: Pan Bian <bianpan2016@163.com>
Signed-off-by: Jan Kara <jack@suse.cz>
---

diff --git a/fs/ext2/xattr.c b/fs/ext2/xattr.c
index 62d9a659a8ff..dd8f10db82e9 100644
--- a/fs/ext2/xattr.c
+++ b/fs/ext2/xattr.c
@@ -612,9 +612,9 @@ skip_replace:
 	}
 
 cleanup:
-	brelse(bh);
 	if (!(bh && header == HDR(bh)))
 		kfree(header);
+	brelse(bh);
 	up_write(&EXT2_I(inode)->xattr_sem);
 
 	return error;