ext2: fix potential use after free
authorPan Bian <bianpan2016@163.com>
Sun, 25 Nov 2018 00:58:02 +0000 (08:58 +0800)
committerJan Kara <jack@suse.cz>
Tue, 27 Nov 2018 09:21:15 +0000 (10:21 +0100)
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>
fs/ext2/xattr.c

index 62d9a659a8ff4e7a3a9556449e35fecc25612e43..dd8f10db82e992da8b8f4fb37699d7bf4a87cf4d 100644 (file)
@@ -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;