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@rbox.co

.../selftests/bpf/prog_tests/sockmap_basic.c | 99 ++++++++++++++++++++++ 1 file changed, 99 insertions(+)

LGTM for the vsock part!

Acked-by: Stefano Garzarella sgarzare@redhat.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