Re: SCSI regression in 4.11

[Christoph Hellwig <hch@lst.de>]

On Thu, Mar 02, 2017 at 01:01:35AM +0100, Christoph Hellwig wrote:
> On Wed, Mar 01, 2017 at 07:54:12AM -0800, Stephen Hemminger wrote:
> > > 	http://git.infradead.org/users/hch/block.git/commitdiff/148cff67b401e2229c076c0ea418712654be77e4
> > 
> > It appears that is already in the code I am testing in linux-next...
> 
> It's in -next now, but it wasn't at the time you reported the bug.
> 
> And it would sortof explain the bug if the INQUIRY data is correct
> in the scatterlist, but we ignore it, given that scsi_probe_lun
> ignores the result based on sense data.
> 
> Can you check what happens with the horrible hack below:

Strike that - we're checking result later, so this can't be the case.

Now the other interesting thing is the memset in __scsi_exectute,
which looks very suspicious.  Try the following please:

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 3e32dc954c3c..22f4fb550561 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -253,7 +253,8 @@ static int __scsi_execute(struct scsi_device *sdev, const unsigned char *cmd,
 	 * and prevent security leaks by zeroing out the excess data.
 	 */
 	if (unlikely(rq->resid_len > 0 && rq->resid_len <= bufflen))
-		memset(buffer + (bufflen - rq->resid_len), 0, rq->resid_len);
+//		memset(buffer + (bufflen - rq->resid_len), 0, rq->resid_len);
+		printk_ratelimited("%s: got resid %d\n", __func__, rq->resid_len);
 
 	if (resid)
 		*resid = rq->resid_len;