scsi: zero per-cmd private driver data for each MQ I/O

commit 1bad6c4a57efda0d5f5bf8a2403b21b1ed24875c upstream.

In lower layer driver's (LLD) scsi_host_template, the driver may
optionally ask SCSI to allocate its private driver memory for each
command, by specifying cmd_size. This memory is allocated at the end of
scsi_cmnd by SCSI.  Later when SCSI queues a command, the LLD can use
scsi_cmd_priv to get to its private data.

Some LLD, e.g. hv_storvsc, doesn't clear its private data before use. In
this case, the LLD may get to stale or uninitialized data in its private
driver memory. This may result in unexpected driver and hardware
behavior.

Fix this problem by also zeroing the private driver memory before
passing them to LLD.

Signed-off-by: Long Li <longli@microsoft.com>
Reviewed-by: Bart Van Assche <Bart.VanAssche@sandisk.com>
Reviewed-by: KY Srinivasan <kys@microsoft.com>
Reviewed-by: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 15c9fe766071a392cbaf49b329c60188cc3e6484..464e7a989cc5c478f3c7e275a56878ca6726d72a 100644 (file)
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -1850,7 +1850,7 @@ static int scsi_mq_prep_fn(struct request *req)
 
        /* zero out the cmd, except for the embedded scsi_request */
        memset((char *)cmd + sizeof(cmd->req), 0,
-               sizeof(*cmd) - sizeof(cmd->req));
+               sizeof(*cmd) - sizeof(cmd->req) + shost->hostt->cmd_size);
 
        req->special = cmd;