netdev - [PATCH net] vsock/bpf: Handle EINTR connect() racing against sockmap update

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Message-Id: <20250307-vsock-trans-signal-race-v1-1-3aca3f771fbd@rbox.co>
Date: Fri, 07 Mar 2025 10:27:50 +0100
From: Michal Luczaj <mhal@...x.co>
To: Stefano Garzarella <sgarzare@...hat.com>, 
 "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, 
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, 
 Simon Horman <horms@...nel.org>, 
 Bobby Eshleman <bobby.eshleman@...edance.com>, 
 "Michael S. Tsirkin" <mst@...hat.com>
Cc: netdev@...r.kernel.org, bpf@...r.kernel.org, 
 Michal Luczaj <mhal@...x.co>
Subject: [PATCH net] vsock/bpf: Handle EINTR connect() racing against
 sockmap update

Signal delivered 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.

Ensure the socket does not stay in sockmap.

WARNING: CPU: 10 PID: 1310 at net/vmw_vsock/vsock_bpf.c:90 vsock_bpf_recvmsg+0xb4b/0xdf0
CPU: 10 UID: 0 PID: 1310 Comm: a.out Tainted: G        W          6.14.0-rc4+
 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")
Signed-off-by: Michal Luczaj <mhal@...x.co>
---
 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 7742a9ae0131310bba197830a241541b2cde6123..e5a6d1d413634f414370595c02bcd77664780d8e 100644
--- a/net/vmw_vsock/af_vsock.c
+++ b/net/vmw_vsock/af_vsock.c
@@ -1581,7 +1581,15 @@ 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;
 }

---
base-commit: b1455a45afcf789f98032ec93c16fea0facdec93
change-id: 20250305-vsock-trans-signal-race-d62f7718d099

Best regards,
-- 
Michal Luczaj <mhal@...x.co>