[PATCH] scsi: sg: don't return bogus Sg_requests

[PATCH] scsi: sg: don't return bogus Sg_requests

[Johannes Thumshirn]

If the list search in sg_get_rq_mark() fails to find a valid request, we
return a bogus element. This then can later lead to a GPF in sg_remove_scat().

So don't return bogus Sg_requests in sg_get_rq_mark() but NULL in case the
list search doesn't find a valid request.

Signed-off-by: Johannes Thumshirn <jthumshirn@suse.de>
Reported-by: Andrey Konovalov <andreyknvl@google.com>
Cc: Hannes Reinecke <hare@suse.de>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Doug Gilbert <dgilbert@interlog.com>
---
 drivers/scsi/sg.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c
index 0a38ba01b7b4..abfde23fa186 100644
--- a/drivers/scsi/sg.c
+++ b/drivers/scsi/sg.c
@@ -2078,7 +2078,7 @@ sg_get_rq_mark(Sg_fd * sfp, int pack_id)
 		}
 	}
 	write_unlock_irqrestore(&sfp->rq_list_lock, iflags);
-	return resp;
+	return (resp->done == 2) ? resp : NULL;
 }
 
 /* always adds to end of list */
-- 
2.12.0

Re: [PATCH] scsi: sg: don't return bogus Sg_requests

[Hannes Reinecke]

On 05/10/2017 09:41 AM, Johannes Thumshirn wrote:
> If the list search in sg_get_rq_mark() fails to find a valid request, we
> return a bogus element. This then can later lead to a GPF in sg_remove_scat().
> 
> So don't return bogus Sg_requests in sg_get_rq_mark() but NULL in case the
> list search doesn't find a valid request.
> 
> Signed-off-by: Johannes Thumshirn <jthumshirn@suse.de>
> Reported-by: Andrey Konovalov <andreyknvl@google.com>
> Cc: Hannes Reinecke <hare@suse.de>
> Cc: Christoph Hellwig <hch@lst.de>
> Cc: Doug Gilbert <dgilbert@interlog.com>
> ---
>  drivers/scsi/sg.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c
> index 0a38ba01b7b4..abfde23fa186 100644
> --- a/drivers/scsi/sg.c
> +++ b/drivers/scsi/sg.c
> @@ -2078,7 +2078,7 @@ sg_get_rq_mark(Sg_fd * sfp, int pack_id)
>  		}
>  	}
>  	write_unlock_irqrestore(&sfp->rq_list_lock, iflags);
> -	return resp;
> +	return (resp->done == 2) ? resp : NULL;
>  }
>  
>  /* always adds to end of list */
> 
Not quite.
Please return 'resp' directly from within the loop.
With this fix we run into the risk that by chance the uninitialized
'resp' pointer contains a '2' at the 'done' location, triggering this
issue again.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		   Teamlead Storage & Networking
hare@suse.de			               +49 911 74053 688
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