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)
---
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;
