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libata: fix NULL sdev dereference race in atapi_qc_complete()

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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 <tj@kernel.org>
Cc: stable@kernel.org
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>
This commit is contained in:
Tejun Heo 2010-11-01 11:39:19 +01:00 committed by Jeff Garzik
parent a0a6da1a73
commit 2a5f07b5ec
1 changed files with 4 additions and 1 deletions
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5
drivers/ata/libata-scsi.c
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@ -2552,8 +2552,11 @@ 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;