From: Andreas Gruenbacher <agruenba@redhat.com>
Date: Mon, 9 Oct 2017 09:13:18 +0000 (+0200)
Subject: direct-io: Prevent NULL pointer access in submit_page_section
X-Git-Tag: v3.10.108~87
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=d75e8540fd8bedc8ee8d11941a7aed3a86735c47;p=thirdparty%2Fkernel%2Fstable.git

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.

Cc: stable@vger.kernel.org # v3.10+
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: Willy Tarreau <w@1wt.eu>
---

diff --git a/fs/direct-io.c b/fs/direct-io.c
index e17d919aa6d83..4007749a478eb 100644
--- a/fs/direct-io.c
+++ b/fs/direct-io.c
@@ -759,7 +759,8 @@ 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;
 	}