releases/4.9.143/ext2-fix-potential-use-after-free.patch

   1 From ecebf55d27a11538ea84aee0be643dd953f830d5 Mon Sep 17 00:00:00 2001
   2 From: Pan Bian <bianpan2016@163.com>
   3 Date: Sun, 25 Nov 2018 08:58:02 +0800
   4 Subject: ext2: fix potential use after free
   5
   6 From: Pan Bian <bianpan2016@163.com>
   7
   8 commit ecebf55d27a11538ea84aee0be643dd953f830d5 upstream.
   9
  10 The function ext2_xattr_set calls brelse(bh) to drop the reference count
  11 of bh. After that, bh may be freed. However, following brelse(bh),
  12 it reads bh->b_data via macro HDR(bh). This may result in a
  13 use-after-free bug. This patch moves brelse(bh) after reading field.
  14
  15 CC: stable@vger.kernel.org
  16 Signed-off-by: Pan Bian <bianpan2016@163.com>
  17 Signed-off-by: Jan Kara <jack@suse.cz>
  18 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  19
  20 ---
  21  fs/ext2/xattr.c |    2 +-
  22  1 file changed, 1 insertion(+), 1 deletion(-)
  23
  24 --- a/fs/ext2/xattr.c
  25 +++ b/fs/ext2/xattr.c
  26 @@ -609,9 +609,9 @@ skip_replace:
  27         }
  28
  29  cleanup:
  30 -       brelse(bh);
  31         if (!(bh && header == HDR(bh)))
  32                 kfree(header);
  33 +       brelse(bh);
  34         up_write(&EXT2_I(inode)->xattr_sem);
  35
  36         return error;