Merge branch 'vsock-fix-so_zerocopy-on-accept-ed-vsocks'

Michal Luczaj says:

====================
vsock: Fix SO_ZEROCOPY on accept()ed vsocks

vsock has its own handling of setsockopt(SO_ZEROCOPY). Which works just
fine unless socket comes from a call to accept(). Because
SOCK_CUSTOM_SOCKOPT flag is missing, attempting to set the option always
results in errno EOPNOTSUPP.
====================

Link: https://patch.msgid.link/20251229-vsock-child-sock-custom-sockopt-v2-0-64778d6c4f88@rbox.co
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

2 files changed, 36 insertions, 0 deletions

diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
index adcba1b7bf74..a3505a4dcee0 100644
--- a/net/vmw_vsock/af_vsock.c
+++ b/net/vmw_vsock/af_vsock.c
@@ -1787,6 +1787,10 @@ static int vsock_accept(struct socket *sock, struct socket *newsock,
 		} else {
 			newsock->state = SS_CONNECTED;
 			sock_graft(connected, newsock);
+
+			set_bit(SOCK_CUSTOM_SOCKOPT,
+				&connected->sk_socket->flags);
+
 			if (vsock_msgzerocopy_allow(vconnected->transport))
 				set_bit(SOCK_SUPPORT_ZC,
 					&connected->sk_socket->flags);
diff --git a/tools/testing/vsock/vsock_test.c b/tools/testing/vsock/vsock_test.c
index 9e1250790f33..bbe3723babdc 100644
--- a/tools/testing/vsock/vsock_test.c
+++ b/tools/testing/vsock/vsock_test.c
@@ -2192,6 +2192,33 @@ static void test_stream_nolinger_server(const struct test_opts *opts)
 	close(fd);
 }
 
+static void test_stream_accepted_setsockopt_client(const struct test_opts *opts)
+{
+	int fd;
+
+	fd = vsock_stream_connect(opts->peer_cid, opts->peer_port);
+	if (fd < 0) {
+		perror("connect");
+		exit(EXIT_FAILURE);
+	}
+
+	close(fd);
+}
+
+static void test_stream_accepted_setsockopt_server(const struct test_opts *opts)
+{
+	int fd;
+
+	fd = vsock_stream_accept(VMADDR_CID_ANY, opts->peer_port, NULL);
+	if (fd < 0) {
+		perror("accept");
+		exit(EXIT_FAILURE);
+	}
+
+	enable_so_zerocopy_check(fd);
+	close(fd);
+}
+
 static struct test_case test_cases[] = {
 	{
 		.name = "SOCK_STREAM connection reset",
@@ -2371,6 +2398,11 @@ static struct test_case test_cases[] = {
 		.run_client = test_seqpacket_unread_bytes_client,
 		.run_server = test_seqpacket_unread_bytes_server,
 	},
+	{
+		.name = "SOCK_STREAM accept()ed socket custom setsockopt()",
+		.run_client = test_stream_accepted_setsockopt_client,
+		.run_server = test_stream_accepted_setsockopt_server,
+	},
 	{},
 };