releases/4.4.93/direct-io-prevent-null-pointer-access-in-submit_page_section.patch

   1 From 899f0429c7d3eed886406cd72182bee3b96aa1f9 Mon Sep 17 00:00:00 2001
   2 From: Andreas Gruenbacher <agruenba@redhat.com>
   3 Date: Mon, 9 Oct 2017 11:13:18 +0200
   4 Subject: direct-io: Prevent NULL pointer access in submit_page_section
   5
   6 From: Andreas Gruenbacher <agruenba@redhat.com>
   7
   8 commit 899f0429c7d3eed886406cd72182bee3b96aa1f9 upstream.
   9
  10 In the code added to function submit_page_section by commit b1058b981,
  11 sdio->bio can currently be NULL when calling dio_bio_submit.  This then
  12 leads to a NULL pointer access in dio_bio_submit, so check for a NULL
  13 bio in submit_page_section before trying to submit it instead.
  14
  15 Fixes xfstest generic/250 on gfs2.
  16
  17 Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
  18 Reviewed-by: Jan Kara <jack@suse.cz>
  19 Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
  20 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  21
  22 ---
  23  fs/direct-io.c |    3 ++-
  24  1 file changed, 2 insertions(+), 1 deletion(-)
  25
  26 --- a/fs/direct-io.c
  27 +++ b/fs/direct-io.c
  28 @@ -823,7 +823,8 @@ out:
  29          */
  30         if (sdio->boundary) {
  31                 ret = dio_send_cur_page(dio, sdio, map_bh);
  32 -               dio_bio_submit(dio, sdio);
  33 +               if (sdio->bio)
  34 +                       dio_bio_submit(dio, sdio);
  35                 page_cache_release(sdio->cur_page);
  36                 sdio->cur_page = NULL;
  37         }