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> --- 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