On 1/8/25 19:06, Stefano Garzarella wrote:
> If the socket has been de-assigned or assigned to another transport,
> we must discard any packets received because they are not expected
> and would cause issues when we access vsk->transport.
>
> A possible scenario is described by Hyunwoo Kim in the attached link,
> where after a first connect() interrupted by a signal, and a second
> connect() failed, we can find `vsk->transport` at NULL, leading to a
> NULL pointer dereference.
>
> Fixes: c0cfa2d8a788 ("vsock: add multi-transports support")
> Reported-by: Hyunwoo Kim <v4bel@xxxxxxxxx>
> Reported-by: Wongi Lee <qwerty@xxxxxxxxx>
> Closes: https://lore.kernel.org/netdev/Z2LvdTTQR7dBmPb5@v4bel-B760M-AORUS-ELITE-AX/
> Signed-off-by: Stefano Garzarella <sgarzare@xxxxxxxxxx>
> ---
> net/vmw_vsock/virtio_transport_common.c | 7 +++++--
> 1 file changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
> index 9acc13ab3f82..51a494b69be8 100644
> --- a/net/vmw_vsock/virtio_transport_common.c
> +++ b/net/vmw_vsock/virtio_transport_common.c
> @@ -1628,8 +1628,11 @@ void virtio_transport_recv_pkt(struct virtio_transport *t,
>
> lock_sock(sk);
>
> - /* Check if sk has been closed before lock_sock */
> - if (sock_flag(sk, SOCK_DONE)) {
> + /* Check if sk has been closed or assigned to another transport before
> + * lock_sock (note: listener sockets are not assigned to any transport)
> + */
> + if (sock_flag(sk, SOCK_DONE) ||
> + (sk->sk_state != TCP_LISTEN && vsk->transport != &t->transport)) {
> (void)virtio_transport_reset_no_sock(t, skb);
> release_sock(sk);
> sock_put(sk);
FWIW, I've tried simplifying Hyunwoo's repro to toy with some tests. Ended
up with
```
from threading import *
from socket import *
from signal import *
def listener(tid):
while True:
s = socket(AF_VSOCK, SOCK_SEQPACKET)
s.bind((1, 1234))
s.listen()
pthread_kill(tid, SIGUSR1)
signal(SIGUSR1, lambda *args: None)
Thread(target=listener, args=[get_ident()]).start()
while True:
c = socket(AF_VSOCK, SOCK_SEQPACKET)
c.connect_ex((1, 1234))
c.connect_ex((42, 1234))
```
which gives me splats with or without this patch.
That said, when I apply this patch, but drop the `sk->sk_state !=
TCP_LISTEN &&`: no more splats.
