linux-kernel - Re: [PATCH RESEND net] vhost: fix vhost_vq_access

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Message-ID: <CAJSP0QXn2jfScW0TYU89792x7jjaPBQjTgQXeGO0nVmKVG1z1Q@mail.gmail.com>
Date:   Tue, 10 Apr 2018 09:05:11 +0800
From:   Stefan Hajnoczi <stefanha@...il.com>
To:     "Michael S. Tsirkin" <mst@...hat.com>
Cc:     David Miller <davem@...emloft.net>, netdev@...r.kernel.org,
        Linux Virtualization <virtualization@...ts.linux-foundation.org>,
        kvm <kvm@...r.kernel.org>, syzkaller-bugs@...glegroups.com,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Stefan Hajnoczi <stefanha@...hat.com>
Subject: Re: [PATCH RESEND net] vhost: fix vhost_vq_access_ok() log check

On Tue, Apr 10, 2018 at 3:40 AM, Michael S. Tsirkin <mst@...hat.com> wrote:
> From: Stefan Hajnoczi <stefanha@...hat.com>
>
> Commit d65026c6c62e7d9616c8ceb5a53b68bcdc050525 ("vhost: validate log
> when IOTLB is enabled") introduced a regression.  The logic was
> originally:
>
>   if (vq->iotlb)
>       return 1;
>   return A && B;
>
> After the patch the short-circuit logic for A was inverted:
>
>   if (A || vq->iotlb)
>       return A;
>   return B;
>
> The correct logic is:
>
>   if (!A || vq->iotlb)
>       return A;
>   return B;
>
> Reported-by: syzbot+65a84dde0214b0387ccd@...kaller.appspotmail.com
> Cc: Jason Wang <jasowang@...hat.com>
> Signed-off-by: Stefan Hajnoczi <stefanha@...hat.com>
> Acked-by: Michael S. Tsirkin <mst@...hat.com>
>
> ---
>  drivers/vhost/vhost.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

NACK

I will send a v2 with cleaner logic as suggested by Linus.

Stefan