selftests/bpf: lsm_cgroup functional test

Functional test that exercises the following:

1. apply default sk_priority policy
2. permit TX-only AF_PACKET socket
3. cgroup attach/detach/replace
4. reusing trampoline shim

Signed-off-by: Stanislav Fomichev <[email protected]>

tools/testing/selftests/bpf/prog_tests/lsm_cgroup.c

@@ -0,0 +1,158 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <test_progs.h>
+
+#include "lsm_cgroup.skel.h"
+#include "cgroup_helpers.h"
+
+void test_lsm_cgroup(void)
+{
+	DECLARE_LIBBPF_OPTS(bpf_prog_attach_opts, attach_opts);
+	DECLARE_LIBBPF_OPTS(bpf_link_update_opts, update_opts);
+	int cgroup_fd, cgroup_fd2, err, fd, prio;
+	struct lsm_cgroup *skel = NULL;
+	int post_create_prog_fd2 = -1;
+	int post_create_prog_fd = -1;
+	int bind_link_fd2 = -1;
+	int bind_prog_fd2 = -1;
+	int alloc_prog_fd = -1;
+	int bind_prog_fd = -1;
+	int bind_link_fd = -1;
+	socklen_t socklen;
+
+	cgroup_fd = test__join_cgroup("/sock_policy");
+	if (!ASSERT_GE(cgroup_fd, 0, "join_cgroup"))
+		goto close_skel;
+
+	cgroup_fd2 = create_and_get_cgroup("/sock_policy2");
+	if (!ASSERT_GE(cgroup_fd2, 0, "create second cgroup"))
+		goto close_skel;
+
+	skel = lsm_cgroup__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "open_and_load"))
+		goto close_cgroup;
+
+	post_create_prog_fd = bpf_program__fd(skel->progs.socket_post_create);
+	post_create_prog_fd2 = bpf_program__fd(skel->progs.socket_post_create2);
+	bind_prog_fd = bpf_program__fd(skel->progs.socket_bind);
+	bind_prog_fd2 = bpf_program__fd(skel->progs.socket_bind2);
+	alloc_prog_fd = bpf_program__fd(skel->progs.socket_alloc);
+
+	err = bpf_prog_attach(alloc_prog_fd, cgroup_fd, BPF_LSM_CGROUP, 0);
+	if (!ASSERT_OK(err, "attach alloc_prog_fd"))
+		goto detach_cgroup;
+
+	/* Make sure replacing works.
+	 */
+
+	err = bpf_prog_attach(post_create_prog_fd, cgroup_fd,
+			      BPF_LSM_CGROUP, 0);
+	if (!ASSERT_OK(err, "attach post_create_prog_fd"))
+		goto close_cgroup;
+
+	attach_opts.replace_prog_fd = post_create_prog_fd;
+	err = bpf_prog_attach_opts(post_create_prog_fd2, cgroup_fd,
+				   BPF_LSM_CGROUP, &attach_opts);
+	if (!ASSERT_OK(err, "prog replace post_create_prog_fd"))
+		goto detach_cgroup;
+
+	/* Try the same attach/replace via link API.
+	 */
+
+	bind_link_fd = bpf_link_create(bind_prog_fd, cgroup_fd,
+				       BPF_LSM_CGROUP, NULL);
+	if (!ASSERT_GE(bind_link_fd, 0, "link create bind_prog_fd"))
+		goto detach_cgroup;
+
+	update_opts.old_prog_fd = bind_prog_fd;
+	update_opts.flags = BPF_F_REPLACE;
+
+	err = bpf_link_update(bind_link_fd, bind_prog_fd2, &update_opts);
+	if (!ASSERT_OK(err, "link update bind_prog_fd"))
+		goto detach_cgroup;
+
+	/* Attach another instance of bind program to another cgroup.
+	 * This should trigger the reuse of the trampoline shim (two
+	 * programs attaching to the same btf_id).
+	 */
+
+	bind_link_fd2 = bpf_link_create(bind_prog_fd2, cgroup_fd2,
+					BPF_LSM_CGROUP, NULL);
+	if (!ASSERT_GE(bind_link_fd2, 0, "link create bind_prog_fd2"))
+		goto detach_cgroup;
+
+	/* AF_UNIX is prohibited.
+	 */
+
+	fd = socket(AF_UNIX, SOCK_STREAM, 0);
+	ASSERT_LT(fd, 0, "socket(AF_UNIX)");
+
+	/* AF_INET6 gets default policy (sk_priority).
+	 */
+
+	fd = socket(AF_INET6, SOCK_STREAM, 0);
+	if (!ASSERT_GE(fd, 0, "socket(SOCK_STREAM)"))
+		goto detach_cgroup;
+
+	prio = 0;
+	socklen = sizeof(prio);
+	ASSERT_GE(getsockopt(fd, SOL_SOCKET, SO_PRIORITY, &prio, &socklen), 0,
+		  "getsockopt");
+	ASSERT_EQ(prio, 123, "sk_priority");
+
+	close(fd);
+
+	/* TX-only AF_PACKET is allowed.
+	 */
+
+	ASSERT_LT(socket(AF_PACKET, SOCK_RAW, htons(ETH_P_ALL)), 0,
+		  "socket(AF_PACKET, ..., ETH_P_ALL)");
+
+	fd = socket(AF_PACKET, SOCK_RAW, 0);
+	ASSERT_GE(fd, 0, "socket(AF_PACKET, ..., 0)");
+
+	/* TX-only AF_PACKET can not be rebound.
+	 */
+
+	struct sockaddr_ll sa = {
+		.sll_family = AF_PACKET,
+		.sll_protocol = htons(ETH_P_ALL),
+	};
+	ASSERT_LT(bind(fd, (struct sockaddr *)&sa, sizeof(sa)), 0,
+		  "bind(ETH_P_ALL)");
+
+	close(fd);
+
+	/* Make sure other cgroup doesn't trigger the programs.
+	 */
+
+	if (!ASSERT_OK(join_cgroup(""), "join root cgroup"))
+		goto detach_cgroup;
+
+	fd = socket(AF_INET6, SOCK_STREAM, 0);
+	if (!ASSERT_GE(fd, 0, "socket(SOCK_STREAM)"))
+		goto detach_cgroup;
+
+	prio = 0;
+	socklen = sizeof(prio);
+	ASSERT_GE(getsockopt(fd, SOL_SOCKET, SO_PRIORITY, &prio, &socklen), 0,
+		  "getsockopt");
+	ASSERT_EQ(prio, 0, "sk_priority");
+
+	close(fd);
+
+detach_cgroup:
+	ASSERT_GE(bpf_prog_detach2(post_create_prog_fd2, cgroup_fd,
+				   BPF_LSM_CGROUP), 0, "detach_create");
+	close(bind_link_fd);
+	/* Don't close bind_link_fd2, exercise cgroup release cleanup. */
+	ASSERT_GE(bpf_prog_detach2(alloc_prog_fd, cgroup_fd,
+				   BPF_LSM_CGROUP), 0, "detach_alloc");
+
+close_cgroup:
+	close(cgroup_fd);
+close_skel:
+	lsm_cgroup__destroy(skel);
+}

tools/testing/selftests/bpf/progs/lsm_cgroup.c

@@ -0,0 +1,94 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include "vmlinux.h"
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+
+char _license[] SEC("license") = "GPL";
+
+#ifndef AF_PACKET
+#define AF_PACKET 17
+#endif
+
+#ifndef AF_UNIX
+#define AF_UNIX 1
+#endif
+
+#ifndef EPERM
+#define EPERM 1
+#endif
+
+static __always_inline int real_create(struct socket *sock, int family,
+				       int protocol)
+{
+	struct sock *sk;
+
+	/* Reject non-tx-only AF_PACKET.
+	 */
+	if (family == AF_PACKET && protocol != 0)
+		return 0; /* EPERM */
+
+	sk = sock->sk;
+	if (!sk)
+		return 1;
+
+	/* The rest of the sockets get default policy.
+	 */
+	sk->sk_priority = 123;
+	return 1;
+}
+
+SEC("lsm_cgroup/socket_post_create")
+int BPF_PROG(socket_post_create, struct socket *sock, int family,
+	     int type, int protocol, int kern)
+{
+	return real_create(sock, family, protocol);
+}
+
+SEC("lsm_cgroup/socket_post_create")
+int BPF_PROG(socket_post_create2, struct socket *sock, int family,
+	     int type, int protocol, int kern)
+{
+	return real_create(sock, family, protocol);
+}
+
+static __always_inline int real_bind(struct socket *sock,
+				     struct sockaddr *address,
+				     int addrlen)
+{
+	struct sockaddr_ll sa = {};
+
+	if (sock->sk->__sk_common.skc_family != AF_PACKET)
+		return 1;
+
+	if (sock->sk->sk_kern_sock)
+		return 1;
+
+	bpf_probe_read_kernel(&sa, sizeof(sa), address);
+	if (sa.sll_protocol)
+		return 0; /* EPERM */
+
+	return 1;
+}
+
+SEC("lsm_cgroup/socket_bind")
+int BPF_PROG(socket_bind, struct socket *sock, struct sockaddr *address,
+	     int addrlen)
+{
+	return real_bind(sock, address, addrlen);
+}
+
+SEC("lsm_cgroup/socket_bind")
+int BPF_PROG(socket_bind2, struct socket *sock, struct sockaddr *address,
+	     int addrlen)
+{
+	return real_bind(sock, address, addrlen);
+}
+
+SEC("lsm_cgroup/sk_alloc_security")
+int BPF_PROG(socket_alloc, struct sock *sk, int family, gfp_t priority)
+{
+	if (family == AF_UNIX)
+		return 0; /* EPERM */
+	return 1;
+}