[PATCH] scsi: Avoid NULL dereferences in scsi_cmd_to_driver

[Mark Rustad <mark.d.rustad@xxxxxxxxx>]

Avoid crashing if the private_data pointer happens to be NULL. This has
been seen sometimes when a host reset happens, notably when there are
many LUNs.

Signed-off-by: Mark Rustad <mark.d.rustad@xxxxxxxxx>
Tested-by: Marcus Dennis <marcusx.e.dennis@xxxxxxxxx>
---

 include/scsi/scsi_cmnd.h |    8 +++++++-
 1 files changed, 7 insertions(+), 1 deletions(-)

diff --git a/include/scsi/scsi_cmnd.h b/include/scsi/scsi_cmnd.h
index 1e11985..ac06cc5 100644
--- a/include/scsi/scsi_cmnd.h
+++ b/include/scsi/scsi_cmnd.h
@@ -134,10 +134,16 @@ struct scsi_cmnd {
 
 static inline struct scsi_driver *scsi_cmd_to_driver(struct scsi_cmnd *cmd)
 {
+	struct scsi_driver **sdp;
+
 	if (!cmd->request->rq_disk)
 		return NULL;
 
-	return *(struct scsi_driver **)cmd->request->rq_disk->private_data;
+	sdp = (struct scsi_driver **)cmd->request->rq_disk->private_data;
+	if (!sdp)
+		return NULL;
+
+	return *sdp;
 }
 
 extern struct scsi_cmnd *scsi_get_command(struct scsi_device *, gfp_t);

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