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@syzkaller.appspotmail.com
Reported-by: Jeongjun Park <aha310510@gmail.com>
Fixes: ced7b713711f ("vhost/vsock: support SEQPACKET for transport").
Tested-by: Arseny Krasnov <arseny.krasnov@kaspersky.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Stefan Hajnoczi <stefanha@redhat.com>
Message-ID: <20240422100010-mutt-send-email-mst@kernel.org>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Reviewed-by: Eugenio Pérez <eperezma@redhat.com>
Acked-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/drivers/vhost/vsock.c b/drivers/vhost/vsock.c
index ec20ecff85c7f470edce5e2537f85e3b9a1f6c35..bf664ec9341b35112df166140892b982230a602c 100644 (file)
--- 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];