linux-kernel - [PATCH 06/13] ide: Potential null pointer dereference in generic_ide

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Message-Id: <1344520529-19164-4-git-send-email-makienko@ispras.ru>
Date:	Thu,  9 Aug 2012 17:55:23 +0400
From:	Marina Makienko <makienko@...ras.ru>
To:	"David S. Miller" <davem@...emloft.net>
Cc:	Marina Makienko <makienko@...ras.ru>, linux-ide@...r.kernel.org,
	linux-kernel@...r.kernel.org, ldv-project@...ras.ru
Subject: [PATCH 06/13] ide: Potential null pointer dereference in generic_ide_resume()

he 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/ide/ide-pm.c |    6 ++++++
 1 files changed, 6 insertions(+), 0 deletions(-)

diff --git a/drivers/ide/ide-pm.c b/drivers/ide/ide-pm.c
index 9240609..4412f24 100644
--- a/drivers/ide/ide-pm.c
+++ b/drivers/ide/ide-pm.c
@@ -19,6 +19,10 @@ int generic_ide_suspend(struct device *dev, pm_message_t mesg)
 
 	memset(&rqpm, 0, sizeof(rqpm));
 	rq = blk_get_request(drive->queue, READ, __GFP_WAIT);
+
+	if (!rq)
+		return -EIO;
+
 	rq->cmd_type = REQ_TYPE_PM_SUSPEND;
 	rq->special = &rqpm;
 	rqpm.pm_step = IDE_PM_START_SUSPEND;
@@ -59,6 +63,8 @@ int generic_ide_resume(struct device *dev)
 
 	memset(&rqpm, 0, sizeof(rqpm));
 	rq = blk_get_request(drive->queue, READ, __GFP_WAIT);
+	if (!rq)
+		return -EIO;
 	rq->cmd_type = REQ_TYPE_PM_RESUME;
 	rq->cmd_flags |= REQ_PREEMPT;
 	rq->special = &rqpm;
-- 
1.7.7

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