Re: [PATCH net 1/2] vsock/virtio: discard packets if the transport changes
From: Michal Luczaj <hidden>
Date: 2025-01-09 13:34:43
Also in:
bpf, kvm, lkml, virtualization
On 1/8/25 19:06, Stefano Garzarella wrote:
quoted hunk ↗ jump to hunk
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 <redacted> Reported-by: Wongi Lee <redacted> Closes: https://lore.kernel.org/netdev/Z2LvdTTQR7dBmPb5@v4bel-B760M-AORUS-ELITE-AX/ (local) Signed-off-by: Stefano Garzarella <sgarzare@redhat.com> --- 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.