From patchwork Thu Aug 9 13:55:21 2012 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Subject: [04/13] ide: Potential null pointer dereference in ide_cdrom_reset() Date: Thu, 09 Aug 2012 03:55:21 -0000 From: Marina Makienko X-Patchwork-Id: 176111 Message-Id: <1344520529-19164-2-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-cd_ioctl.c | 4 ++++ 1 files changed, 4 insertions(+), 0 deletions(-) diff --git a/drivers/ide/ide-cd_ioctl.c b/drivers/ide/ide-cd_ioctl.c index 02caa7d..e29588f 100644 --- a/drivers/ide/ide-cd_ioctl.c +++ b/drivers/ide/ide-cd_ioctl.c @@ -304,6 +304,10 @@ int ide_cdrom_reset(struct cdrom_device_info *cdi) int ret; rq = blk_get_request(drive->queue, READ, __GFP_WAIT); + + if (!rq) + return -EIO; + rq->cmd_type = REQ_TYPE_SPECIAL; rq->cmd_flags = REQ_QUIET; ret = blk_execute_rq(drive->queue, cd->disk, rq, 0);