Re: [scsi 1/2] scsi_debug: schedule_resp fix input variable check

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On 15-02-23 06:13 AM, Tomas Winkler wrote:
The function should never be called with cmnd NULL so
put a fat WARN there.
Fix also smatch wraning:
schedule_resp() warn: variable dereferenced before check 'cmnd'

Signed-off-by: Tomas Winkler <tomas.winkler@xxxxxxxxx>
---
  drivers/scsi/scsi_debug.c | 11 +++++++++--
  1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/drivers/scsi/scsi_debug.c b/drivers/scsi/scsi_debug.c
index ccbe1282e975..f032aac75997 100644
--- a/drivers/scsi/scsi_debug.c
+++ b/drivers/scsi/scsi_debug.c
@@ -3947,11 +3947,18 @@ schedule_resp(struct scsi_cmnd *cmnd, struct sdebug_dev_info *devip,
  	struct sdebug_queued_cmd *sqcp = NULL;
  	struct scsi_device *sdp = cmnd->device;

This patch seems incorrect because it still dereferences
cmnd (in the above line) before it checks it for NULL.

-	if (NULL == cmnd || NULL == devip) {
-		pr_warn("called with NULL cmnd or devip pointer\n");
+	/* this should never happend */

happen?

The scsi_debug driver was written by Eric Youngdale to test
the original Linux SCSI subsystem (or a subsequent rewrite
of same). Remnants of its "trust nobody" style remain and
may have been of use to more recent tinkerers.

+	if (WARN_ON(!cmnd))
+		return SCSI_MLQUEUE_HOST_BUSY;
+
+	if (NULL == devip) {

if (unlikely(NULL == devip)) {

+		pr_warn("called devip == NULL\n");
  		/* no particularly good error to report back */
  		return SCSI_MLQUEUE_HOST_BUSY;
  	}
+
+	sdp = cmnd->device;
+
  	if ((scsi_result) && (SCSI_DEBUG_OPT_NOISE & scsi_debug_opts))
  		sdev_printk(KERN_INFO, sdp, "%s: non-zero result=0x%x\n",
  			    __func__, scsi_result);


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