Merge branch 'so_passrights'

Kuniyuki Iwashima says:
====================

af_unix: Introduce SO_PASSRIGHTS.

As long as recvmsg() or recvmmsg() is used with cmsg, it is not
possible to avoid receiving file descriptors via SCM_RIGHTS.

This series introduces a new socket option, SO_PASSRIGHTS, to allow
disabling SCM_RIGHTS.  The option is enabled by default.

See patch 8 for background/context.

This series is related to [0], but is split into a separate series,
as most of the patches are specific to af_unix.

The v2 of the BPF LSM extension part will be posted later, once
this series is merged into net-next and has landed in bpf-next.

[0]: https://lore.kernel.org/bpf/20250505215802.48449-1-kuniyu@amazon.com/

Changes:
  v5:
    * Patch 4
      * Fix BPF selftest failure (setget_sockopt.c)

  v4: https://lore.kernel.org/netdev/20250515224946.6931-1-kuniyu@amazon.com/
    * Patch 6
      * Group sk->sk_scm_XXX bits by struct
    * Patch 9
      * Remove errno handling

  v3: https://lore.kernel.org/netdev/20250514165226.40410-1-kuniyu@amazon.com/
    * Patch 3
      * Remove inline in scm.c
    * Patch 4 & 5 & 8
      * Return -EOPNOTSUPP in getsockopt()
    * Patch 5
      * Add CONFIG_SECURITY_NETWORK check for SO_PASSSEC
    * Patch 6
      * Add kdoc for sk_scm_unused
      * Update sk_scm_XXX under lock_sock() in setsockopt()
    * Patch 7
      * Update changelog (recent change -> aed6ecef55d7)

  v2: https://lore.kernel.org/netdev/20250510015652.9931-1-kuniyu@amazon.com/
    * Added patch 4 & 5 to reuse sk_txrehash for scm_recv() flags

  v1: https://lore.kernel.org/netdev/20250508013021.79654-1-kuniyu@amazon.com/
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

3 files changed, 91 insertions, 2 deletions

diff --git a/tools/include/uapi/asm-generic/socket.h b/tools/include/uapi/asm-generic/socket.h
index aa5016ff3d91..f333a0ac4ee4 100644
--- a/tools/include/uapi/asm-generic/socket.h
+++ b/tools/include/uapi/asm-generic/socket.h
@@ -145,6 +145,8 @@
 
 #define SO_RCVPRIORITY		82
 
+#define SO_PASSRIGHTS		83
+
 #if !defined(__KERNEL__)
 
 #if __BITS_PER_LONG == 64 || (defined(__x86_64__) && defined(__ILP32__))
diff --git a/tools/testing/selftests/bpf/progs/setget_sockopt.c b/tools/testing/selftests/bpf/progs/setget_sockopt.c
index 0107a24b7522..d330b1511979 100644
--- a/tools/testing/selftests/bpf/progs/setget_sockopt.c
+++ b/tools/testing/selftests/bpf/progs/setget_sockopt.c
@@ -83,6 +83,14 @@ struct loop_ctx {
 	struct sock *sk;
 };
 
+static bool sk_is_tcp(struct sock *sk)
+{
+	return (sk->__sk_common.skc_family == AF_INET ||
+		sk->__sk_common.skc_family == AF_INET6) &&
+		sk->sk_type == SOCK_STREAM &&
+		sk->sk_protocol == IPPROTO_TCP;
+}
+
 static int bpf_test_sockopt_flip(void *ctx, struct sock *sk,
 				 const struct sockopt_test *t,
 				 int level)
@@ -91,6 +99,9 @@ static int bpf_test_sockopt_flip(void *ctx, struct sock *sk,
 
 	opt = t->opt;
 
+	if (opt == SO_TXREHASH && !sk_is_tcp(sk))
+		return 0;
+
 	if (bpf_getsockopt(ctx, level, opt, &old, sizeof(old)))
 		return 1;
 	/* kernel initialized txrehash to 255 */
diff --git a/tools/testing/selftests/net/af_unix/scm_rights.c b/tools/testing/selftests/net/af_unix/scm_rights.c
index d66336256580..8b015f16c03d 100644
--- a/tools/testing/selftests/net/af_unix/scm_rights.c
+++ b/tools/testing/selftests/net/af_unix/scm_rights.c
@@ -23,6 +23,7 @@ FIXTURE_VARIANT(scm_rights)
 	int type;
 	int flags;
 	bool test_listener;
+	bool disabled;
 };
 
 FIXTURE_VARIANT_ADD(scm_rights, dgram)
@@ -31,6 +32,16 @@ FIXTURE_VARIANT_ADD(scm_rights, dgram)
 	.type = SOCK_DGRAM,
 	.flags = 0,
 	.test_listener = false,
+	.disabled = false,
+};
+
+FIXTURE_VARIANT_ADD(scm_rights, dgram_disabled)
+{
+	.name = "UNIX ",
+	.type = SOCK_DGRAM,
+	.flags = 0,
+	.test_listener = false,
+	.disabled = true,
 };
 
 FIXTURE_VARIANT_ADD(scm_rights, stream)
@@ -39,6 +50,16 @@ FIXTURE_VARIANT_ADD(scm_rights, stream)
 	.type = SOCK_STREAM,
 	.flags = 0,
 	.test_listener = false,
+	.disabled = false,
+};
+
+FIXTURE_VARIANT_ADD(scm_rights, stream_disabled)
+{
+	.name = "UNIX-STREAM ",
+	.type = SOCK_STREAM,
+	.flags = 0,
+	.test_listener = false,
+	.disabled = true,
 };
 
 FIXTURE_VARIANT_ADD(scm_rights, stream_oob)
@@ -47,6 +68,16 @@ FIXTURE_VARIANT_ADD(scm_rights, stream_oob)
 	.type = SOCK_STREAM,
 	.flags = MSG_OOB,
 	.test_listener = false,
+	.disabled = false,
+};
+
+FIXTURE_VARIANT_ADD(scm_rights, stream_oob_disabled)
+{
+	.name = "UNIX-STREAM ",
+	.type = SOCK_STREAM,
+	.flags = MSG_OOB,
+	.test_listener = false,
+	.disabled = true,
 };
 
 FIXTURE_VARIANT_ADD(scm_rights, stream_listener)
@@ -55,6 +86,16 @@ FIXTURE_VARIANT_ADD(scm_rights, stream_listener)
 	.type = SOCK_STREAM,
 	.flags = 0,
 	.test_listener = true,
+	.disabled = false,
+};
+
+FIXTURE_VARIANT_ADD(scm_rights, stream_listener_disabled)
+{
+	.name = "UNIX-STREAM ",
+	.type = SOCK_STREAM,
+	.flags = 0,
+	.test_listener = true,
+	.disabled = true,
 };
 
 FIXTURE_VARIANT_ADD(scm_rights, stream_listener_oob)
@@ -63,6 +104,16 @@ FIXTURE_VARIANT_ADD(scm_rights, stream_listener_oob)
 	.type = SOCK_STREAM,
 	.flags = MSG_OOB,
 	.test_listener = true,
+	.disabled = false,
+};
+
+FIXTURE_VARIANT_ADD(scm_rights, stream_listener_oob_disabled)
+{
+	.name = "UNIX-STREAM ",
+	.type = SOCK_STREAM,
+	.flags = MSG_OOB,
+	.test_listener = true,
+	.disabled = true,
 };
 
 static int count_sockets(struct __test_metadata *_metadata,
@@ -105,6 +156,9 @@ FIXTURE_SETUP(scm_rights)
 	ret = unshare(CLONE_NEWNET);
 	ASSERT_EQ(0, ret);
 
+	if (variant->disabled)
+		return;
+
 	ret = count_sockets(_metadata, variant);
 	ASSERT_EQ(0, ret);
 }
@@ -113,6 +167,9 @@ FIXTURE_TEARDOWN(scm_rights)
 {
 	int ret;
 
+	if (variant->disabled)
+		return;
+
 	sleep(1);
 
 	ret = count_sockets(_metadata, variant);
@@ -121,6 +178,7 @@ FIXTURE_TEARDOWN(scm_rights)
 
 static void create_listeners(struct __test_metadata *_metadata,
 			     FIXTURE_DATA(scm_rights) *self,
+			     const FIXTURE_VARIANT(scm_rights) *variant,
 			     int n)
 {
 	struct sockaddr_un addr = {
@@ -140,6 +198,12 @@ static void create_listeners(struct __test_metadata *_metadata,
 		ret = listen(self->fd[i], -1);
 		ASSERT_EQ(0, ret);
 
+		if (variant->disabled) {
+			ret = setsockopt(self->fd[i], SOL_SOCKET, SO_PASSRIGHTS,
+					 &(int){0}, sizeof(int));
+			ASSERT_EQ(0, ret);
+		}
+
 		addrlen = sizeof(addr);
 		ret = getsockname(self->fd[i], (struct sockaddr *)&addr, &addrlen);
 		ASSERT_EQ(0, ret);
@@ -164,6 +228,12 @@ static void create_socketpairs(struct __test_metadata *_metadata,
 	for (i = 0; i < n * 2; i += 2) {
 		ret = socketpair(AF_UNIX, variant->type, 0, self->fd + i);
 		ASSERT_EQ(0, ret);
+
+		if (variant->disabled) {
+			ret = setsockopt(self->fd[i], SOL_SOCKET, SO_PASSRIGHTS,
+					 &(int){0}, sizeof(int));
+			ASSERT_EQ(0, ret);
+		}
 	}
 }
 
@@ -175,7 +245,7 @@ static void __create_sockets(struct __test_metadata *_metadata,
 	ASSERT_LE(n * 2, sizeof(self->fd) / sizeof(self->fd[0]));
 
 	if (variant->test_listener)
-		create_listeners(_metadata, self, n);
+		create_listeners(_metadata, self, variant, n);
 	else
 		create_socketpairs(_metadata, self, variant, n);
 }
@@ -230,7 +300,13 @@ void __send_fd(struct __test_metadata *_metadata,
 	int ret;
 
 	ret = sendmsg(self->fd[receiver * 2 + 1], &msg, variant->flags);
-	ASSERT_EQ(MSGLEN, ret);
+
+	if (variant->disabled) {
+		ASSERT_EQ(-1, ret);
+		ASSERT_EQ(-EPERM, -errno);
+	} else {
+		ASSERT_EQ(MSGLEN, ret);
+	}
 }
 
 #define create_sockets(n)					\