From 23ce422748def9652fdc019f740cd7900fa2fe3b Mon Sep 17 00:00:00 2001
From: Philipp Reisner <philipp.reisner@linbit.com>
Date: Thu, 20 May 2010 13:35:31 +0200
Subject: [PATCH] drbd: Null pointer deref fix to the large "multi bio rewrite"

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
---
 drivers/block/drbd/drbd_receiver.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/block/drbd/drbd_receiver.c b/drivers/block/drbd/drbd_receiver.c
index 461d9872d4d3..bc9ab7fb2cc7 100644
--- a/drivers/block/drbd/drbd_receiver.c
+++ b/drivers/block/drbd/drbd_receiver.c
@@ -98,6 +98,10 @@ static struct page *page_chain_del(struct page **head, int n)
 	BUG_ON(!head);
 
 	page = *head;
+
+	if (!page)
+		return NULL;
+
 	while (page) {
 		tmp = page_chain_next(page);
 		if (--n == 0)