netdev - Re: [PATCH net-next v3 5/7] vsock/test: Add test for accept

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Message-ID: <mnqfajtappfhgav2wqxbxi53bvnstqhwjhtdnarlmlp3uy7tid@rqcuvan7ky4b>
Date: Wed, 18 Dec 2024 18:56:07 +0100
From: Stefano Garzarella <sgarzare@...hat.com>
To: Michal Luczaj <mhal@...x.co>
Cc: netdev@...r.kernel.org
Subject: Re: [PATCH net-next v3 5/7] vsock/test: Add test for accept_queue
 memory leak

On Wed, Dec 18, 2024 at 03:32:38PM +0100, Michal Luczaj wrote:
>Attempt to enqueue a child after the queue was flushed, but before
>SOCK_DONE flag has been set.
>
>Test tries to produce a memory leak, kmemleak should be employed. Dealing
>with a race condition, test by its very nature may lead to a false
>negative.
>
>Fixed by commit d7b0ff5a8667 ("virtio/vsock: Fix accept_queue memory
>leak").
>
>Signed-off-by: Michal Luczaj <mhal@...x.co>
>---
> tools/testing/vsock/vsock_test.c | 52 ++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 52 insertions(+)

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

>
>diff --git a/tools/testing/vsock/vsock_test.c b/tools/testing/vsock/vsock_test.c
>index 8bb2ab41c55f5c4d76e89903f80411915296c44e..2a8fcb062d9d207be988da5dd350e503ca20a143 100644
>--- a/tools/testing/vsock/vsock_test.c
>+++ b/tools/testing/vsock/vsock_test.c
>@@ -29,6 +29,10 @@
> #include "control.h"
> #include "util.h"
>
>+/* Basic messages for control_writeulong(), control_readulong() */
>+#define CONTROL_CONTINUE	1
>+#define CONTROL_DONE		0
>+
> static void test_stream_connection_reset(const struct test_opts *opts)
> {
> 	union {
>@@ -1474,6 +1478,49 @@ static void test_stream_cred_upd_on_set_rcvlowat(const struct test_opts *opts)
> 	test_stream_credit_update_test(opts, false);
> }
>
>+/* The goal of test leak_acceptq is to stress the race between connect() and
>+ * close(listener). Implementation of client/server loops boils down to:
>+ *
>+ * client                server
>+ * ------                ------
>+ * write(CONTINUE)
>+ *                       expect(CONTINUE)
>+ *                       listen()
>+ *                       write(LISTENING)
>+ * expect(LISTENING)
>+ * connect()             close()
>+ */
>+#define ACCEPTQ_LEAK_RACE_TIMEOUT 2 /* seconds */
>+
>+static void test_stream_leak_acceptq_client(const struct test_opts *opts)
>+{
>+	time_t tout;
>+	int fd;
>+
>+	tout = current_nsec() + ACCEPTQ_LEAK_RACE_TIMEOUT * NSEC_PER_SEC;
>+	do {
>+		control_writeulong(CONTROL_CONTINUE);
>+
>+		fd = vsock_stream_connect(opts->peer_cid, opts->peer_port);
>+		if (fd >= 0)
>+			close(fd);
>+	} while (current_nsec() < tout);
>+
>+	control_writeulong(CONTROL_DONE);
>+}
>+
>+/* Test for a memory leak. User is expected to run kmemleak scan, see README. */
>+static void test_stream_leak_acceptq_server(const struct test_opts *opts)
>+{
>+	int fd;
>+
>+	while (control_readulong() == CONTROL_CONTINUE) {
>+		fd = vsock_stream_listen(VMADDR_CID_ANY, opts->peer_port);
>+		control_writeln("LISTENING");
>+		close(fd);
>+	}
>+}
>+
> static struct test_case test_cases[] = {
> 	{
> 		.name = "SOCK_STREAM connection reset",
>@@ -1604,6 +1651,11 @@ static struct test_case test_cases[] = {
> 		.run_client = test_seqpacket_unsent_bytes_client,
> 		.run_server = test_seqpacket_unsent_bytes_server,
> 	},
>+	{
>+		.name = "SOCK_STREAM leak accept queue",
>+		.run_client = test_stream_leak_acceptq_client,
>+		.run_server = test_stream_leak_acceptq_server,
>+	},
> 	{},
> };
>
>
>-- 
>2.47.1
>