> But now that it's explained, the bugfix as proposed is incomplete:
> userspace can set features twice and the second time will leak
> old VIRTIO_VSOCK_F_SEQPACKET bit value.
>
> And I am pretty sure the Fixes tag is wrong.
>
> So I wrote this, but I actually don't have a set for
> seqpacket to test this. Arseny could you help test maybe?
> Thanks!
Hi! Sorry for late reply! Just run vsock test suite with this patch -
seems everything is ok!
>
>
> commit bcc17a060d93b198d8a17a9b87b593f41337ee28
> Author: Michael S. Tsirkin <mst@xxxxxxxxxx>
> Date: Mon Apr 22 10:03:13 2024 -0400
>
> vhost/vsock: always initialize seqpacket_allow
>
> 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>
>
> 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];
