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Date: Thu, 27 Jul 2017 10:01:38 +0200
From: Cornelia Huck <cohuck@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH 2/2] s390x/css: fix bits must be zero check
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To: Halil Pasic <pasic@linux.vnet.ibm.com>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>, Dong Jia Shi <bjsdjshi@linux.vnet.ibm.com>, qemu-devel@nongnu.org

On Wed, 26 Jul 2017 00:44:42 +0200
Halil Pasic <pasic@linux.vnet.ibm.com> wrote:

> According to the PoP bit positions 0-3 and 8-32 of the format-1 CCW must
> contain zeros.  Bits 0-3 are already covered by cmd_code validity
> checking, and bit 32 is covered by the CCW address checking.
> 
> Bits 8-31 correspond to CCW1.flags and CCW1.count.  Currently we only
> check for the absence of certain flags.  Let's fix this.
> 
> Signed-off-by: Halil Pasic <pasic@linux.vnet.ibm.com>
> ---
>  hw/s390x/css.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/hw/s390x/css.c b/hw/s390x/css.c
> index d17e21b7af..1f04ce4a1b 100644
> --- a/hw/s390x/css.c
> +++ b/hw/s390x/css.c
> @@ -884,7 +884,8 @@ static int css_interpret_ccw(SubchDev *sch, hwaddr ccw_addr,
>              ret = -EINVAL;
>              break;
>          }
> -        if (ccw.flags & (CCW_FLAG_CC | CCW_FLAG_DC)) {
> +        if (ccw.flags || ccw.count) {
> +            /* We have already sanitized these if fmt 0. */

I'd tweak that to

/* We have already sanitized these if converted from fmt 0. */

Seems less confusing.

>              ret = -EINVAL;
>              break;
>          }

I'm inclined to pick this as a 2.10 bugfix. Patch 1 still needs work
from what I've seen.