Re: [PATCH] vhost/vsock: always initialize seqpacket_allow

[Eugenio Perez Martin]

On Wed, May 15, 2024 at 5:05 PM Michael S. Tsirkin <mst@xxxxxxxxxx> wrote:
>
> There are two issues around seqpacket_allow:
> 1. seqpacket_allow is not initialized when socket is
>    created. Thus if features are never set, it will be
>    read uninitialized.
> 2. if VIRTIO_VSOCK_F_SEQPACKET is set and then cleared,
>    then seqpacket_allow will not be cleared appropriately
>    (existing apps I know about don't usually do this but
>     it's legal and there's no way to be sure no one relies
>     on this).
>
> To fix:
>         - initialize seqpacket_allow after allocation
>         - set it unconditionally in set_features
>
> Reported-by: syzbot+6c21aeb59d0e82eb2782@xxxxxxxxxxxxxxxxxxxxxxxxx
> Reported-by: Jeongjun Park <aha310510@xxxxxxxxx>
> Fixes: ced7b713711f ("vhost/vsock: support SEQPACKET for transport").
> Cc: Arseny Krasnov <arseny.krasnov@xxxxxxxxxxxxx>
> Cc: David S. Miller <davem@xxxxxxxxxxxxx>
> Cc: Stefan Hajnoczi <stefanha@xxxxxxxxxx>
> Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
> Acked-by: Arseniy Krasnov <avkrasnov@xxxxxxxxxxxxxxxxx>
> Tested-by: Arseniy Krasnov <avkrasnov@xxxxxxxxxxxxxxxxx>
>

Reviewed-by: Eugenio Pérez <eperezma@xxxxxxxxxx>

Thanks!

> ---
>
>
> Reposting now it's been tested.
>
>  drivers/vhost/vsock.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/vhost/vsock.c b/drivers/vhost/vsock.c
> index ec20ecff85c7..bf664ec9341b 100644
> --- a/drivers/vhost/vsock.c
> +++ b/drivers/vhost/vsock.c
> @@ -667,6 +667,7 @@ static int vhost_vsock_dev_open(struct inode *inode, struct file *file)
>         }
>
>         vsock->guest_cid = 0; /* no CID assigned yet */
> +       vsock->seqpacket_allow = false;
>
>         atomic_set(&vsock->queued_replies, 0);
>
> @@ -810,8 +811,7 @@ static int vhost_vsock_set_features(struct vhost_vsock *vsock, u64 features)
>                         goto err;
>         }
>
> -       if (features & (1ULL << VIRTIO_VSOCK_F_SEQPACKET))
> -               vsock->seqpacket_allow = true;
> +       vsock->seqpacket_allow = features & (1ULL << VIRTIO_VSOCK_F_SEQPACKET);
>
>         for (i = 0; i < ARRAY_SIZE(vsock->vqs); i++) {
>                 vq = &vsock->vqs[i];
> --
> MST
>