3w-xxxx: fix oops caused by incorrect REQUEST_SENSE handling

3w-xxxx emulates a REQUEST_SENSE response by simply returning nothing.
Unfortunately, it's assuming that the REQUEST_SENSE command is
implemented with use_sg == 0, which is no longer the case.  The oops
occurs because it's clearing the scatterlist in request_buffer instead
of the memory region.

This is fixed by using tw_transfer_internal() to transfer correctly to
the scatterlist.
Acked-by: adam radford <aradford@gmail.com>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/scsi/3w-xxxx.c

@@ -1864,10 +1864,17 @@ static int tw_scsiop_read_write(TW_Device_Extension *tw_dev, int request_id)
 /* This function will handle the request sense scsi command */
 static int tw_scsiop_request_sense(TW_Device_Extension *tw_dev, int request_id)
 {
+	char request_buffer[18];
+
 	dprintk(KERN_NOTICE "3w-xxxx: tw_scsiop_request_sense()\n");
 
-	/* For now we just zero the request buffer */
-	memset(tw_dev->srb[request_id]->request_buffer, 0, tw_dev->srb[request_id]->request_bufflen);
+	memset(request_buffer, 0, sizeof(request_buffer));
+	request_buffer[0] = 0x70; /* Immediate fixed format */
+	request_buffer[7] = 10;	/* minimum size per SPC: 18 bytes */
+	/* leave all other fields zero, giving effectively NO_SENSE return */
+	tw_transfer_internal(tw_dev, request_id, request_buffer,
+			     sizeof(request_buffer));
+
 	tw_dev->state[request_id] = TW_S_COMPLETED;
 	tw_state_request_finish(tw_dev, request_id);