direct-io: Prevent NULL pointer access in submit_page_section

BugLink: http://bugs.launchpad.net/bugs/1724669
commit 899f0429c7d3eed886406cd72182bee3b96aa1f9 upstream.

In the code added to function submit_page_section by commit b1058b981,
sdio->bio can currently be NULL when calling dio_bio_submit.  This then
leads to a NULL pointer access in dio_bio_submit, so check for a NULL
bio in submit_page_section before trying to submit it instead.

Fixes xfstest generic/250 on gfs2.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Seth Forshee <seth.forshee@canonical.com>

diff --git a/fs/direct-io.c b/fs/direct-io.c
index 08cf27811e5af22b62a5330a2f21b0d0af25de77..ad379f082d831717caad9681a358b79af7ce39f9 100644 (file)
--- a/fs/direct-io.c
+++ b/fs/direct-io.c
@@ -838,7 +838,8 @@ out:
         */
        if (sdio->boundary) {
                ret = dio_send_cur_page(dio, sdio, map_bh);
-               dio_bio_submit(dio, sdio);
+               if (sdio->bio)
+                       dio_bio_submit(dio, sdio);
                put_page(sdio->cur_page);
                sdio->cur_page = NULL;
        }