linux-kernel - [PATCH 13/13] scsi: Potential null pointer dereference in scsi_eh_lock

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Date:	Thu,  9 Aug 2012 17:55:50 +0400
From:	Marina Makienko <makienko@...ras.ru>
To:	Mike Anderson <andmike@...ibm.com>
Cc:	Marina Makienko <makienko@...ras.ru>,
	"James E.J. Bottomley" <JBottomley@...allels.com>,
	linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org,
	ldv-project@...ras.ru
Subject: [PATCH 13/13] scsi: Potential null pointer dereference in scsi_eh_lock_door()

The function blk_get_request() can return NULL in some cases. There are
checks on it if function is called with argumetns one of which is
GFP_ATOMIC/GFP_NOIO/etc. If system couldn't find request
blk_get_request() return NULL.

But if there is function call with argument __GFP_WAIT
the system will wait until get request or the queue becomes
dead. If something kills the queue, blk_get_request()
return NULL and next operations will lead to errors.

Found by Linux Driver Verification project (linuxtesting.org).

Signed-off-by: Marina Makienko <makienko@...ras.ru>
---
 drivers/scsi/scsi_error.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/drivers/scsi/scsi_error.c b/drivers/scsi/scsi_error.c
index 4a6381c..7dd67d4 100644
--- a/drivers/scsi/scsi_error.c
+++ b/drivers/scsi/scsi_error.c
@@ -1624,6 +1624,9 @@ static void scsi_eh_lock_door(struct scsi_device *sdev)
 	 */
 	req = blk_get_request(sdev->request_queue, READ, GFP_KERNEL);
 
+	if (!req)
+		return;
+
 	req->cmd[0] = ALLOW_MEDIUM_REMOVAL;
 	req->cmd[1] = 0;
 	req->cmd[2] = 0;
-- 
1.7.7

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