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References: <20220826161605.559317-1-maxime.coquelin@redhat.com>
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From:   Jason Wang <jasowang@redhat.com>
Date:   Mon, 29 Aug 2022 08:44:17 +0800
Message-ID: <CACGkMEt=WOBuF0M7PyY_y4pdpANW96_ku78cRuCKTR4-v+_q_Q@mail.gmail.com>
Subject: Re: [PATCH] vduse: prevent uninitialized memory accesses
To:     Maxime Coquelin <maxime.coquelin@redhat.com>
Cc:     linux-kernel <linux-kernel@vger.kernel.org>,
        virtualization <virtualization@lists.linux-foundation.org>,
        Eli Cohen <elic@nvidia.com>,
        Guanjun <guanjun@linux.alibaba.com>,
        Parav Pandit <parav@nvidia.com>,
        Gautam Dawar <gautam.dawar@xilinx.com>,
        Dan Carpenter <dan.carpenter@oracle.com>,
        Yongji Xie <xieyongji@bytedance.com>, mst <mst@redhat.com>
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On Sat, Aug 27, 2022 at 12:16 AM Maxime Coquelin
<maxime.coquelin@redhat.com> wrote:
>
> If the VDUSE application provides a smaller config space
> than the driver expects, the driver may use uninitialized
> memory from the stack.
>
> This patch prevents it by initializing the buffer passed by
> the driver to store the config value.
>
> Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>

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

> ---
>  drivers/vdpa/vdpa_user/vduse_dev.c | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/vdpa/vdpa_user/vduse_dev.c b/drivers/vdpa/vdpa_user/vduse_dev.c
> index 41c0b29739f1..35dceee3ed56 100644
> --- a/drivers/vdpa/vdpa_user/vduse_dev.c
> +++ b/drivers/vdpa/vdpa_user/vduse_dev.c
> @@ -673,10 +673,15 @@ static void vduse_vdpa_get_config(struct vdpa_device *vdpa, unsigned int offset,
>  {
>         struct vduse_dev *dev = vdpa_to_vduse(vdpa);
>
> -       if (offset > dev->config_size ||
> -           len > dev->config_size - offset)
> +       /* Initialize the buffer in case of partial copy. */
> +       memset(buf, 0, len);
> +
> +       if (offset > dev->config_size)
>                 return;
>
> +       if (len > dev->config_size - offset)
> +               len = dev->config_size - offset;
> +
>         memcpy(buf, dev->config + offset, len);
>  }
>
> --
> 2.37.1
>