linux-kernel - Re: [PATCH v2] scsi: sg: don't return bogus Sg

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Message-ID: <ec8d85ca-10c6-b857-049d-74fedc55aba7@interlog.com>
Date:   Wed, 10 May 2017 15:37:56 -0400
From:   Douglas Gilbert <dgilbert@...erlog.com>
To:     Johannes Thumshirn <jthumshirn@...e.de>,
        "Martin K . Petersen" <martin.petersen@...cle.com>
Cc:     James Bottomley <jejb@...ux.vnet.ibm.com>,
        Andrey Konovalov <andreyknvl@...gle.com>,
        Linux Kernel Mailinglist <linux-kernel@...r.kernel.org>,
        Linux SCSI Mailinglist <linux-scsi@...r.kernel.org>,
        Hannes Reinecke <hare@...e.de>, Christoph Hellwig <hch@....de>
Subject: Re: [PATCH v2] scsi: sg: don't return bogus Sg_requests

On 2017-05-10 03:53 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@...e.de>
> Reported-by: Andrey Konovalov <andreyknvl@...gle.com>
> Cc: Hannes Reinecke <hare@...e.de>
> Cc: Christoph Hellwig <hch@....de>
> Cc: Doug Gilbert <dgilbert@...erlog.com>
> ---
> Changes to v1:
> * Directly return found element within the loop (Hannes)
>
>  drivers/scsi/sg.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c
> index 0a38ba01b7b4..82c33a6edbea 100644
> --- a/drivers/scsi/sg.c
> +++ b/drivers/scsi/sg.c
> @@ -2074,11 +2074,12 @@ sg_get_rq_mark(Sg_fd * sfp, int pack_id)
>  		if ((1 == resp->done) && (!resp->sg_io_owned) &&
>  		    ((-1 == pack_id) || (resp->header.pack_id == pack_id))) {
>  			resp->done = 2;	/* guard against other readers */
> -			break;
> +			write_unlock_irqrestore(&sfp->rq_list_lock, iflags);
> +			return resp;
>  		}
>  	}
>  	write_unlock_irqrestore(&sfp->rq_list_lock, iflags);
> -	return resp;
> +	return NULL;
>  }
>
>  /* always adds to end of list */
>

Acked-by: Douglas Gilbert <dgilbert@...erlog.com>