Re: [PATCH 2/2 v4] vdpa: check that offsets are within bounds

From: Jason Wang <jasowang@redhat.com>
To: Dan Carpenter <dan.carpenter@oracle.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>,
	"Tiwei Bie" <tiwei.bie@intel.com>,
	"Xie Yongji" <xieyongji@bytedance.com>,
	"Eugenio Pérez" <eperezma@redhat.com>, kvm <kvm@vger.kernel.org>,
	virtualization <virtualization@lists.linux-foundation.org>,
	kernel-janitors@vger.kernel.org
Subject: Re: [PATCH 2/2 v4] vdpa: check that offsets are within bounds
Date: Thu, 9 Dec 2021 10:12:39 +0800	[thread overview]
Message-ID: <CACGkMEtp+29Y4zcUppakRmQLqKbkUfFN-dm6a70bvn9GUCrWRA@mail.gmail.com> (raw)
In-Reply-To: <20211208103337.GA4047@kili>

On Wed, Dec 8, 2021 at 6:34 PM Dan Carpenter <dan.carpenter@oracle.com> wrote:
>
> In this function "c->off" is a u32 and "size" is a long.  On 64bit systems
> if "c->off" is greater than "size" then "size - c->off" is a negative and
> we always return -E2BIG.  But on 32bit systems the subtraction is type
> promoted to a high positive u32 value and basically any "c->len" is
> accepted.
>
> Fixes: 4c8cf31885f6 ("vhost: introduce vDPA-based backend")
> Reported-by: Xie Yongji <xieyongji@bytedance.com>
> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>

Acked-by: Jason Wang <jasowang@redhat.com>

> ---
> v4: split into a separate patch
>
>  drivers/vhost/vdpa.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
> index 29cced1cd277..e3c4f059b21a 100644
> --- a/drivers/vhost/vdpa.c
> +++ b/drivers/vhost/vdpa.c
> @@ -197,7 +197,7 @@ static int vhost_vdpa_config_validate(struct vhost_vdpa *v,
>         struct vdpa_device *vdpa = v->vdpa;
>         long size = vdpa->config->get_config_size(vdpa);
>
> -       if (c->len == 0)
> +       if (c->len == 0 || c->off > size)
>                 return -EINVAL;
>
>         if (c->len > size - c->off)
> --
> 2.20.1
>