From patchwork Thu Aug 9 13:55:20 2012 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Subject: [03/13] ide: Potential null pointer dereference in ide_queue_pc_tail() Date: Thu, 09 Aug 2012 03:55:20 -0000 From: Marina Makienko X-Patchwork-Id: 176103 Message-Id: <1344520529-19164-1-git-send-email-makienko@ispras.ru> To: "David S. Miller" Cc: Marina Makienko , linux-ide@vger.kernel.org, linux-kernel@vger.kernel.org, ldv-project@ispras.ru 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 --- drivers/ide/ide-atapi.c | 6 ++++++ 1 files changed, 6 insertions(+), 0 deletions(-) diff --git a/drivers/ide/ide-atapi.c b/drivers/ide/ide-atapi.c index fac3d9d..8bf4109 100644 --- a/drivers/ide/ide-atapi.c +++ b/drivers/ide/ide-atapi.c @@ -93,6 +93,12 @@ int ide_queue_pc_tail(ide_drive_t *drive, struct gendisk *disk, int error; rq = blk_get_request(drive->queue, READ, __GFP_WAIT); + + if (!rq) { + printk(KERN_ERR PFX"ide_queue_pc_tail: blk_get_request() failed. \n"); + return 1; + } + rq->cmd_type = REQ_TYPE_SPECIAL; rq->special = (char *)pc;