selftests/bpf: fix memory leak of lsm_cgroup

kmemleak reports this issue:

unreferenced object 0xffff88810b7835c0 (size 32):
  comm "test_progs", pid 270, jiffies 4294969007 (age 1621.315s)
  hex dump (first 32 bytes):
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
    03 00 00 00 03 00 00 00 0f 00 00 00 00 00 00 00  ................
  backtrace:
    [<00000000376cdeab>] kmalloc_trace+0x27/0x110
    [<000000003bcdb3b6>] selinux_sk_alloc_security+0x66/0x110
    [<000000003959008f>] security_sk_alloc+0x47/0x80
    [<00000000e7bc6668>] sk_prot_alloc+0xbd/0x1a0
    [<0000000002d6343a>] sk_alloc+0x3b/0x940
    [<000000009812a46d>] unix_create1+0x8f/0x3d0
    [<000000005ed0976b>] unix_create+0xa1/0x150
    [<0000000086a1d27f>] __sock_create+0x233/0x4a0
    [<00000000cffe3a73>] __sys_socket_create.part.0+0xaa/0x110
    [<0000000007c63f20>] __sys_socket+0x49/0xf0
    [<00000000b08753c8>] __x64_sys_socket+0x42/0x50
    [<00000000b56e26b3>] do_syscall_64+0x3b/0x90
    [<000000009b4871b8>] entry_SYSCALL_64_after_hwframe+0x63/0xcd

The issue occurs in the following scenarios:

unix_create1()
  sk_alloc()
    sk_prot_alloc()
      security_sk_alloc()
        call_int_hook()
          hlist_for_each_entry()
            entry1->hook.sk_alloc_security
            <-- selinux_sk_alloc_security() succeeded,
            <-- sk->security alloced here.
            entry2->hook.sk_alloc_security
            <-- bpf_lsm_sk_alloc_security() failed
      goto out_free;
        ...    <-- the sk->security not freed, memleak

The core problem is that the LSM is not yet fully stacked (work is
actively going on in this space) which means that some LSM hooks do
not support multiple LSMs at the same time. To fix, skip the
"EPERM" test when it runs in the environments that already have
non-bpf lsms installed

Fixes: dca85aac88 ("selftests/bpf: lsm_cgroup functional test")
Signed-off-by: Wang Yufen <wangyufen@huawei.com>
Cc: Stanislav Fomichev <sdf@google.com>
Acked-by: Stanislav Fomichev <sdf@google.com>
Link: https://lore.kernel.org/r/1668482980-16163-1-git-send-email-wangyufen@huawei.com
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>

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

@@ -173,9 +173,11 @@ static void test_lsm_cgroup_functional(void)
 	ASSERT_EQ(query_prog_cnt(cgroup_fd, NULL), 4, "total prog count");
 	ASSERT_EQ(query_prog_cnt(cgroup_fd2, NULL), 1, "total prog count");
 
-	/* AF_UNIX is prohibited. */
-
 	fd = socket(AF_UNIX, SOCK_STREAM, 0);
+	if (!(skel->kconfig->CONFIG_SECURITY_APPARMOR
+	    || skel->kconfig->CONFIG_SECURITY_SELINUX
+	    || skel->kconfig->CONFIG_SECURITY_SMACK))
+		/* AF_UNIX is prohibited. */
 		ASSERT_LT(fd, 0, "socket(AF_UNIX)");
 	close(fd);
 
@@ -233,10 +235,17 @@ static void test_lsm_cgroup_functional(void)
 
 	/* AF_INET6+SOCK_STREAM
 	 * AF_PACKET+SOCK_RAW
+	 * AF_UNIX+SOCK_RAW if already have non-bpf lsms installed
 	 * listen_fd
 	 * client_fd
 	 * accepted_fd
 	 */
+	if (skel->kconfig->CONFIG_SECURITY_APPARMOR
+	    || skel->kconfig->CONFIG_SECURITY_SELINUX
+	    || skel->kconfig->CONFIG_SECURITY_SMACK)
+		/* AF_UNIX+SOCK_RAW if already have non-bpf lsms installed */
+		ASSERT_EQ(skel->bss->called_socket_post_create2, 6, "called_create2");
+	else
 		ASSERT_EQ(skel->bss->called_socket_post_create2, 5, "called_create2");
 
 	/* start_server

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

@@ -7,6 +7,10 @@
 
 char _license[] SEC("license") = "GPL";
 
+extern bool CONFIG_SECURITY_SELINUX __kconfig __weak;
+extern bool CONFIG_SECURITY_SMACK __kconfig __weak;
+extern bool CONFIG_SECURITY_APPARMOR __kconfig __weak;
+
 #ifndef AF_PACKET
 #define AF_PACKET 17
 #endif
@@ -140,6 +144,10 @@ SEC("lsm_cgroup/sk_alloc_security")
 int BPF_PROG(socket_alloc, struct sock *sk, int family, gfp_t priority)
 {
 	called_socket_alloc++;
+	/* if already have non-bpf lsms installed, EPERM will cause memory leak of non-bpf lsms */
+	if (CONFIG_SECURITY_SELINUX || CONFIG_SECURITY_SMACK || CONFIG_SECURITY_APPARMOR)
+		return 1;
+
 	if (family == AF_UNIX)
 		return 0; /* EPERM */