linux-kernel - [PATCH 3.10 054/139] direct-io: Prevent NULL pointer access in submit_page

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Date:   Wed,  1 Nov 2017 22:25:55 +0100
From:   Willy Tarreau <w@....eu>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        linux@...ck-us.net
Cc:     Andreas Gruenbacher <agruenba@...hat.com>,
        Al Viro <viro@...iv.linux.org.uk>, Willy Tarreau <w@....eu>
Subject: [PATCH 3.10 054/139] direct-io: Prevent NULL pointer access in submit_page_section

From: Andreas Gruenbacher <agruenba@...hat.com>

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.

Cc: stable@...r.kernel.org 
Signed-off-by: Andreas Gruenbacher <agruenba@...hat.com>
Reviewed-by: Jan Kara <jack@...e.cz>
Signed-off-by: Al Viro <viro@...iv.linux.org.uk>
Signed-off-by: Willy Tarreau <w@....eu>
---
 fs/direct-io.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/fs/direct-io.c b/fs/direct-io.c
index e17d919..85485c1 100644
--- a/fs/direct-io.c
+++ b/fs/direct-io.c
@@ -760,6 +760,8 @@ 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);
 		page_cache_release(sdio->cur_page);
 		sdio->cur_page = NULL;
 	}
-- 
2.8.0.rc2.1.gbe9624a