From f9139a1a2457323894c1780f0e44271af807346d Mon Sep 17 00:00:00 2001
From: Andreas Gruenbacher <agruenba@redhat.com>
Date: Mon, 9 Oct 2017 11:13:18 +0200
Subject: direct-io: Prevent NULL pointer access in submit_page_section

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>

diff --git a/fs/direct-io.c b/fs/direct-io.c
index c60756e..c6220a2 100644
--- a/fs/direct-io.c
+++ b/fs/direct-io.c
@@ -835,7 +835,8 @@ 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;
 	}
-- 
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