linux-kernel - Re: [PATCH] vhost/vsock: always initialize seqpacket

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Message-ID: <CAJaqyWd9-fhrxBv3gTq82bGnSVdC_vw_LXg+XVNHT3B6cD0VOg@mail.gmail.com>
Date: Thu, 16 May 2024 15:37:42 +0200
From: Eugenio Perez Martin <eperezma@...hat.com>
To: "Michael S. Tsirkin" <mst@...hat.com>
Cc: linux-kernel@...r.kernel.org, 
	syzbot+6c21aeb59d0e82eb2782@...kaller.appspotmail.com, 
	Jeongjun Park <aha310510@...il.com>, Arseny Krasnov <arseny.krasnov@...persky.com>, 
	"David S . Miller" <davem@...emloft.net>, Stefan Hajnoczi <stefanha@...hat.com>, 
	Stefano Garzarella <sgarzare@...hat.com>, Jason Wang <jasowang@...hat.com>, kvm@...r.kernel.org, 
	virtualization@...ts.linux.dev, netdev@...r.kernel.org
Subject: Re: [PATCH] vhost/vsock: always initialize seqpacket_allow

On Wed, May 15, 2024 at 5:05 PM Michael S. Tsirkin <mst@...hat.com> 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@...kaller.appspotmail.com
> Reported-by: Jeongjun Park <aha310510@...il.com>
> Fixes: ced7b713711f ("vhost/vsock: support SEQPACKET for transport").
> Cc: Arseny Krasnov <arseny.krasnov@...persky.com>
> Cc: David S. Miller <davem@...emloft.net>
> Cc: Stefan Hajnoczi <stefanha@...hat.com>
> Signed-off-by: Michael S. Tsirkin <mst@...hat.com>
> Acked-by: Arseniy Krasnov <avkrasnov@...utedevices.com>
> Tested-by: Arseniy Krasnov <avkrasnov@...utedevices.com>
>

Reviewed-by: Eugenio Pérez <eperezma@...hat.com>

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
>