[PATCH bpf-next v2 3/3] selftests/bpf: Test forbidden bpf_ksock_sendto() LSM attach

[Mahe Tardy <mahe.tardy@gmail.com>]

Similarly to '7b0dfbf5776b ("selftests/bpf: Test forbidden
bpf_ksock_send() LSM attach")', tests that the verifier filter prevents
bpf_ksock_sendto() to be called in a LSM program attached to
security_socket_sendmsg() as it would create a direct recursion.

Signed-off-by: Mahe Tardy <mahe.tardy@gmail.com>
---
 .../selftests/bpf/progs/ksock_lsm_verifier.c  | 25 ++++++++++++++++++-
 1 file changed, 24 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/bpf/progs/ksock_lsm_verifier.c b/tools/testing/selftests/bpf/progs/ksock_lsm_verifier.c
index fd2ccfdb5802..9533570eb340 100644
--- a/tools/testing/selftests/bpf/progs/ksock_lsm_verifier.c
+++ b/tools/testing/selftests/bpf/progs/ksock_lsm_verifier.c
@@ -12,7 +12,7 @@ char send_data[11] = "dummy data";
 SEC("lsm.s/socket_sendmsg")
 __description("bpf_ksock_send is rejected from socket_sendmsg LSM hook")
 __failure __msg("calling kernel function bpf_ksock_send is not allowed")
-int BPF_PROG(ksock_socket_sendmsg, struct socket *sock, struct msghdr *msg,
+int BPF_PROG(socket_sendmsg_ksock_send, struct socket *sock, struct msghdr *msg,
 	     int size, int ret)
 {
 	struct __ksock_ctx_value *v;
@@ -32,4 +32,27 @@ int BPF_PROG(ksock_socket_sendmsg, struct socket *sock, struct msghdr *msg,
 	return ret;
 }

+SEC("lsm.s/socket_sendmsg")
+__description("bpf_ksock_sendto is rejected from socket_sendmsg LSM hook")
+__failure __msg("calling kernel function bpf_ksock_sendto is not allowed")
+int BPF_PROG(socket_sendmsg_ksock_sendto, struct socket *sock,
+	     struct msghdr *msg, int size, int ret)
+{
+	struct __ksock_ctx_value *v;
+	struct bpf_ksock *ks;
+
+	v = ksock_ctx_value_lookup();
+	if (!v)
+		return ret;
+
+	ks = bpf_kptr_xchg(&v->ctx, NULL);
+	if (!ks)
+		return ret;
+
+	bpf_ksock_sendto(ks, send_data, sizeof(send_data), NULL, 0);
+	bpf_ksock_release(ks);
+
+	return ret;
+}
+
 char __license[] SEC("license") = "GPL";
--
2.43.0