From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tejun Heo Subject: [PATCH #upstream-fixes] libata: fix NULL sdev dereference race in atapi_qc_complete() Date: Mon, 01 Nov 2010 11:39:19 +0100 Message-ID: <4CCE98D7.1030906@kernel.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: Received: from hera.kernel.org ([140.211.167.34]:53998 "EHLO hera.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753722Ab0KAKjq (ORCPT ); Mon, 1 Nov 2010 06:39:46 -0400 Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: Jeff Garzik , "linux-ide@vger.kernel.org" , stable SCSI commands may be issued between __scsi_add_device() and dev->sdev assignment, so it's unsafe for ata_qc_complete() to dereference dev->sdev->locked without checking whether it's NULL or not. Fix it. Signed-off-by: Tejun Heo Cc: stable@kernel.org --- I actually hit this race condition. Lucky me. :-) Thanks. drivers/ata/libata-scsi.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) Index: work/drivers/ata/libata-scsi.c =================================================================== --- work.orig/drivers/ata/libata-scsi.c +++ work/drivers/ata/libata-scsi.c @@ -2552,8 +2552,11 @@ static void atapi_qc_complete(struct ata * * If door lock fails, always clear sdev->locked to * avoid this infinite loop. + * + * This may happen before SCSI scan is complete. Make + * sure qc->dev->sdev isn't NULL before dereferencing. */ - if (qc->cdb[0] == ALLOW_MEDIUM_REMOVAL) + if (qc->cdb[0] == ALLOW_MEDIUM_REMOVAL && qc->dev->sdev) qc->dev->sdev->locked = 0; qc->scsicmd->result = SAM_STAT_CHECK_CONDITION;