On Sat, Sep 19, 2026 at 5:32 AM Bartłomiej Dmitruk <[email protected]> wrote: > > The send hook vmci_transport_dgram_allow() refuses datagrams when the socket's > netns is not in global mode (vsock_net_mode_global()), but the receive path > (vmci_transport_recv_dgram_cb() -> vmci_transport_allow_dgram()) did not, so a > socket bound in a non-global (local) netns received datagrams from peers it > could never send to, defeating namespace isolation. > > Add the check at the start of the receive decision, before the > VMADDR_CID_HYPERVISOR short-circuit, so the hypervisor CID is covered too > (matching the send side). > > This was found by code inspection; I do not have VMCI hardware to test on > (compile-tested only). > > Fixes: eafb64f40ca4 ("vsock: add netns to vsock core") > Signed-off-by: Bartłomiej Dmitruk <[email protected]> > Assisted-by: Claude (Anthropic)
Reviewed-by: Vishnu Dasa <[email protected]> > --- > v2: perform the netns check first (before the hypervisor early return) so > hypervisor datagrams are also gated in local mode -- the Sashiko AI review > noted v1 left that path partially bypassed. > v1: > https://lore.kernel.org/netdev/[email protected]/ > > diff --git a/net/vmw_vsock/vmci_transport.c b/net/vmw_vsock/vmci_transport.c > --- a/net/vmw_vsock/vmci_transport.c > +++ b/net/vmw_vsock/vmci_transport.c > @@ -532,6 +532,14 @@ > static bool vmci_transport_allow_dgram(struct vsock_sock *vsock, u32 > peer_cid) > { > u64 access; > + > + /* Enforce the per-netns mode first, symmetrically with the send hook > + * vmci_transport_dgram_allow(): a socket in a non-global (local) > netns > + * must not receive datagrams it could never send (this also covers > the > + * hypervisor CID). > + */ > + if (!vsock_net_mode_global(vsock)) > + return false; > > if (VMADDR_CID_HYPERVISOR == peer_cid) > return true;
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