[PATCH net v2 1/3] vsock/bpf: Fix EINTR connect() racing sockmap update

From: Michal Luczaj
Date: Fri Mar 14 2025 - 11:21:28 EST


Signal delivery during connect() may result in a disconnect of an already
TCP_ESTABLISHED socket. Problem is that such established socket might have
been placed in a sockmap before the connection was closed. We end up with a
SS_UNCONNECTED vsock in a sockmap. And this, combined with the ability to
reassign (unconnected) vsock's transport to NULL, breaks the sockmap
contract. As manifested by WARN_ON_ONCE.

connect
/ state = SS_CONNECTED /
sock_map_update_elem
if signal_pending
state = SS_UNCONNECTED

connect
transport = NULL
vsock_bpf_recvmsg
WARN_ON_ONCE(!vsk->transport)

Ensure the socket does not stay in sockmap.

WARNING: CPU: 8 PID: 1228 at net/vmw_vsock/vsock_bpf.c:97 vsock_bpf_recvmsg+0xb43/0xe00
CPU: 8 UID: 0 PID: 1228 Comm: a.out Not tainted 6.14.0-rc5+
RIP: 0010:vsock_bpf_recvmsg+0xb43/0xe00
sock_recvmsg+0x1b2/0x220
__sys_recvfrom+0x190/0x270
__x64_sys_recvfrom+0xdc/0x1b0
do_syscall_64+0x93/0x1b0
entry_SYSCALL_64_after_hwframe+0x76/0x7e

Fixes: 634f1a7110b4 ("vsock: support sockmap")
Reviewed-by: Stefano Garzarella <sgarzare@xxxxxxxxxx>
Signed-off-by: Michal Luczaj <mhal@xxxxxxx>
---
net/vmw_vsock/af_vsock.c | 10 +++++++++-
net/vmw_vsock/vsock_bpf.c | 1 +
2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
index 7e3db87ae4333cf63327ec105ca99253569bb9fe..81b1b8e9c946a646778367ab78ca180cef75ef72 100644
--- a/net/vmw_vsock/af_vsock.c
+++ b/net/vmw_vsock/af_vsock.c
@@ -1579,7 +1579,15 @@ static int vsock_connect(struct socket *sock, struct sockaddr *addr,

if (signal_pending(current)) {
err = sock_intr_errno(timeout);
- sk->sk_state = sk->sk_state == TCP_ESTABLISHED ? TCP_CLOSING : TCP_CLOSE;
+ if (sk->sk_state == TCP_ESTABLISHED) {
+ /* Might have raced with a sockmap update. */
+ if (sk->sk_prot->unhash)
+ sk->sk_prot->unhash(sk);
+
+ sk->sk_state = TCP_CLOSING;
+ } else {
+ sk->sk_state = TCP_CLOSE;
+ }
sock->state = SS_UNCONNECTED;
vsock_transport_cancel_pkt(vsk);
vsock_remove_connected(vsk);
diff --git a/net/vmw_vsock/vsock_bpf.c b/net/vmw_vsock/vsock_bpf.c
index 07b96d56f3a577af71021b1b8132743554996c4f..c68fdaf09046b68254dac3ea70ffbe73dfa45cef 100644
--- a/net/vmw_vsock/vsock_bpf.c
+++ b/net/vmw_vsock/vsock_bpf.c
@@ -127,6 +127,7 @@ static void vsock_bpf_rebuild_protos(struct proto *prot, const struct proto *bas
{
*prot = *base;
prot->close = sock_map_close;
+ prot->unhash = sock_map_unhash;
prot->recvmsg = vsock_bpf_recvmsg;
prot->sock_is_readable = sk_msg_is_readable;
}

--
2.48.1