From: Tejun Heo Date: Mon, 1 Nov 2010 10:39:19 +0000 (+0100) Subject: libata: fix NULL sdev dereference race in atapi_qc_complete() X-Git-Tag: v2.6.34.9~142 X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=b8d823c716dceeb1a6b4c6b6883a4f61a5f429df;p=thirdparty%2Fkernel%2Fstable.git libata: fix NULL sdev dereference race in atapi_qc_complete() commit 2a5f07b5ec098edc69e05fdd2f35d3fbb1235723 upstream. 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 Signed-off-by: Jeff Garzik Signed-off-by: Paul Gortmaker --- diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c index 0088cdeb0b1ee..1d266e222a5cc 100644 --- a/drivers/ata/libata-scsi.c +++ b/drivers/ata/libata-scsi.c @@ -2548,8 +2548,11 @@ static void atapi_qc_complete(struct ata_queued_cmd *qc) * * 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;