linux-kernel - Re: [PATCH net v4 2/3] selftest/bpf: Add test for AF

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Message-ID: <hlfjllms6ih53rdw45apgajek6fp4ljnfxlwkr2efyqcuf6fqo@rj6yjmj4fjem>
Date: Wed, 19 Mar 2025 10:17:18 +0100
From: Stefano Garzarella <sgarzare@...hat.com>
To: Michal Luczaj <mhal@...x.co>
Cc: "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>, 
	"Michael S. Tsirkin" <mst@...hat.com>, Bobby Eshleman <bobby.eshleman@...edance.com>, 
	Andrii Nakryiko <andrii@...nel.org>, Eduard Zingerman <eddyz87@...il.com>, 
	Mykola Lysenko <mykolal@...com>, Alexei Starovoitov <ast@...nel.org>, 
	Daniel Borkmann <daniel@...earbox.net>, Martin KaFai Lau <martin.lau@...ux.dev>, 
	Song Liu <song@...nel.org>, Yonghong Song <yonghong.song@...ux.dev>, 
	John Fastabend <john.fastabend@...il.com>, KP Singh <kpsingh@...nel.org>, 
	Stanislav Fomichev <sdf@...ichev.me>, Hao Luo <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>, 
	Shuah Khan <shuah@...nel.org>, netdev@...r.kernel.org, bpf@...r.kernel.org, 
	virtualization@...ts.linux.dev, linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org
Subject: Re: [PATCH net v4 2/3] selftest/bpf: Add test for AF_VSOCK connect()
 racing sockmap update

On Mon, Mar 17, 2025 at 10:52:24AM +0100, Michal Luczaj wrote:
>Racing signal-interrupted connect() and sockmap update may result in an
>unconnected (and missing vsock transport) socket in a sockmap.
>
>Test spends 2 seconds attempting to reach 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)
>
>Signed-off-by: Michal Luczaj <mhal@...x.co>
>---
> .../selftests/bpf/prog_tests/sockmap_basic.c       | 99 ++++++++++++++++++++++
> 1 file changed, 99 insertions(+)

LGTM for the vsock part!

Acked-by: Stefano Garzarella <sgarzare@...hat.com>

>
>diff --git a/tools/testing/selftests/bpf/prog_tests/sockmap_basic.c b/tools/testing/selftests/bpf/prog_tests/sockmap_basic.c
>index 1e3e4392dcca0e1722c1982ecc649a80c27443b2..2f8bba27866354848f1e30b5473cedb6a85244ff 100644
>--- a/tools/testing/selftests/bpf/prog_tests/sockmap_basic.c
>+++ b/tools/testing/selftests/bpf/prog_tests/sockmap_basic.c
>@@ -3,6 +3,7 @@
> #include <error.h>
> #include <netinet/tcp.h>
> #include <sys/epoll.h>
>+#include <linux/time64.h>
>
> #include "test_progs.h"
> #include "test_skmsg_load_helpers.skel.h"
>@@ -1042,6 +1043,102 @@ static void test_sockmap_vsock_unconnected(void)
> 	xclose(map);
> }
>
>+#define CONNECT_SIGNAL_RACE_TIMEOUT 2 /* seconds */
>+
>+static void sig_handler(int signum)
>+{
>+	/* nop */
>+}
>+
>+static void connect_signal_racer_cleanup(void *map)
>+{
>+	xclose(*(int *)map);
>+}
>+
>+static void *connect_signal_racer(void *arg)
>+{
>+	pid_t pid;
>+	int map;
>+
>+	map = bpf_map_create(BPF_MAP_TYPE_SOCKMAP, NULL, sizeof(int),
>+			     sizeof(int), 1, NULL);
>+	if (!ASSERT_OK_FD(map, "bpf_map_create"))
>+		return NULL;
>+
>+	pthread_cleanup_push(connect_signal_racer_cleanup, &map);
>+	pid = getpid();
>+
>+	for (;;) {
>+		int c = *(int *)arg;
>+		int zero = 0;
>+
>+		(void)bpf_map_update_elem(map, &zero, &c, BPF_ANY);
>+
>+		if (kill(pid, SIGUSR1)) {
>+			FAIL_ERRNO("kill");
>+			break;
>+		}
>+
>+		if ((recv(c, NULL, 0, MSG_DONTWAIT) < 0) && errno == ENODEV) {
>+			FAIL_ERRNO("recv");
>+			break;
>+		}
>+	}
>+
>+	pthread_cleanup_pop(1);
>+
>+	return NULL;
>+}
>+
>+static void test_sockmap_vsock_connect_signal_race(void)
>+{
>+	struct sockaddr_vm addr, bad_addr;
>+	socklen_t alen = sizeof(addr);
>+	sighandler_t orig_handler;
>+	pthread_t thread;
>+	int s, c, p;
>+	__u64 tout;
>+
>+	orig_handler = signal(SIGUSR1, sig_handler);
>+	if (!ASSERT_NEQ(orig_handler, SIG_ERR, "signal handler setup"))
>+		return;
>+
>+	s = socket_loopback(AF_VSOCK, SOCK_SEQPACKET | SOCK_NONBLOCK);
>+	if (s < 0)
>+		goto restore;
>+
>+	if (xgetsockname(s, (struct sockaddr *)&addr, &alen))
>+		goto close;
>+
>+	bad_addr = addr;
>+	bad_addr.svm_cid = 0x42424242; /* non-existing */
>+
>+	if (xpthread_create(&thread, 0, connect_signal_racer, &c))
>+		goto close;
>+
>+	tout = get_time_ns() + CONNECT_SIGNAL_RACE_TIMEOUT * NSEC_PER_SEC;
>+	do {
>+		c = xsocket(AF_VSOCK, SOCK_SEQPACKET, 0);
>+		if (c < 0)
>+			break;
>+
>+		if (connect(c, (struct sockaddr *)&addr, alen) && errno == EINTR)
>+			(void)connect(c, (struct sockaddr *)&bad_addr, alen);
>+
>+		xclose(c);
>+		p = accept(s, NULL, NULL);
>+		if (p >= 0)
>+			xclose(p);
>+	} while (get_time_ns() < tout);
>+
>+	ASSERT_OK(pthread_cancel(thread), "pthread_cancel");
>+	xpthread_join(thread, NULL);
>+close:
>+	xclose(s);
>+restore:
>+	ASSERT_NEQ(signal(SIGUSR1, orig_handler), SIG_ERR, "handler restore");
>+}
>+
> void test_sockmap_basic(void)
> {
> 	if (test__start_subtest("sockmap create_update_free"))
>@@ -1108,4 +1205,6 @@ void test_sockmap_basic(void)
> 		test_sockmap_skb_verdict_vsock_poll();
> 	if (test__start_subtest("sockmap vsock unconnected"))
> 		test_sockmap_vsock_unconnected();
>+	if (test__start_subtest("sockmap vsock connect signal race"))
>+		test_sockmap_vsock_connect_signal_race();
> }
>
>-- 
>2.48.1
>