linux-kernel - Re: [PATCH] virtio-gpu: fix a missing check to avoid NULL dereference

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Date:   Mon, 28 Mar 2022 14:08:20 -0700
From:   Chia-I Wu <olvaffe@...il.com>
To:     Xiaomeng Tong <xiam0nd.tong@...il.com>
Cc:     David Airlie <airlied@...ux.ie>, Gerd Hoffmann <kraxel@...hat.com>,
        Gurchetan Singh <gurchetansingh@...omium.org>,
        Daniel Vetter <daniel@...ll.ch>,
        Dave Airlie <airlied@...hat.com>,
        ML dri-devel <dri-devel@...ts.freedesktop.org>,
        "open list:VIRTIO CORE, NET AND BLOCK DRIVERS" 
        <virtualization@...ts.linux-foundation.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] virtio-gpu: fix a missing check to avoid NULL dereference

On Sat, Mar 26, 2022 at 10:09 PM Xiaomeng Tong <xiam0nd.tong@...il.com> wrote:
>
> 'cache_ent' could be set NULL inside virtio_gpu_cmd_get_capset()
> and it will lead to a NULL dereference by a lately use of it
> (i.e., ptr = cache_ent->caps_cache). Fix it with a NULL check.
>
> Fixes: 62fb7a5e10962 ("virtio-gpu: add 3d/virgl support")
> Signed-off-by: Xiaomeng Tong <xiam0nd.tong@...il.com>
Reviewed-by: Chia-I Wu <olvaffe@...il.com>
> ---
>  drivers/gpu/drm/virtio/virtgpu_ioctl.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/virtio/virtgpu_ioctl.c b/drivers/gpu/drm/virtio/virtgpu_ioctl.c
> index c708bab555c6..b0f1c4d8fd23 100644
> --- a/drivers/gpu/drm/virtio/virtgpu_ioctl.c
> +++ b/drivers/gpu/drm/virtio/virtgpu_ioctl.c
> @@ -579,8 +579,10 @@ static int virtio_gpu_get_caps_ioctl(struct drm_device *dev,
>         spin_unlock(&vgdev->display_info_lock);
>
>         /* not in cache - need to talk to hw */
> -       virtio_gpu_cmd_get_capset(vgdev, found_valid, args->cap_set_ver,
> +       ret = virtio_gpu_cmd_get_capset(vgdev, found_valid, args->cap_set_ver,
>                                   &cache_ent);
> +       if (ret)
> +               return ret;
>         virtio_gpu_notify(vgdev);
>
>  copy_exit:
>
> base-commit: f443e374ae131c168a065ea1748feac6b2e76613
> --
> 2.17.1
>