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Subject[34-longterm 068/209] libata: fix NULL sdev dereference race in atapi_qc_complete()
Date
From: Tejun Heo <tj@kernel.org>

=====================================================================
| This is a commit scheduled for the next v2.6.34 longterm release. |
| If you see a problem with using this for longterm, please comment.|
=====================================================================

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 <tj@kernel.org>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
---
drivers/ata/libata-scsi.c | 5 ++++-
1 files changed, 4 insertions(+), 1 deletions(-)

diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c
index 0088cde..1d266e2 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;
--
1.7.4.4


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