selftests/bpf: Cover verifier checks for mutating sockmap/sockhash

Verifier enforces that only certain program types can mutate sock{map,hash}
maps, that is update it or delete from it. Add test coverage for these
checks so we don't regress.

Signed-off-by: Jakub Sitnicki <jakub@cloudflare.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/20240527-sockmap-verify-deletes-v1-3-944b372f2101@cloudflare.com

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

@@ -67,6 +67,7 @@
 #include "verifier_search_pruning.skel.h"
 #include "verifier_sock.skel.h"
 #include "verifier_sock_addr.skel.h"
+#include "verifier_sockmap_mutate.skel.h"
 #include "verifier_spill_fill.skel.h"
 #include "verifier_spin_lock.skel.h"
 #include "verifier_stack_ptr.skel.h"
@@ -183,6 +184,7 @@ void test_verifier_sdiv(void)                 { RUN(verifier_sdiv); }
 void test_verifier_search_pruning(void)       { RUN(verifier_search_pruning); }
 void test_verifier_sock(void)                 { RUN(verifier_sock); }
 void test_verifier_sock_addr(void)            { RUN(verifier_sock_addr); }
+void test_verifier_sockmap_mutate(void)       { RUN(verifier_sockmap_mutate); }
 void test_verifier_spill_fill(void)           { RUN(verifier_spill_fill); }
 void test_verifier_spin_lock(void)            { RUN(verifier_spin_lock); }
 void test_verifier_stack_ptr(void)            { RUN(verifier_stack_ptr); }

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

@@ -0,0 +1,187 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+
+#include "bpf_misc.h"
+
+#define __always_unused __attribute__((unused))
+
+char _license[] SEC("license") = "GPL";
+
+struct sock {
+} __attribute__((preserve_access_index));
+
+struct bpf_iter__sockmap {
+	union {
+		struct sock *sk;
+	};
+} __attribute__((preserve_access_index));
+
+struct {
+	__uint(type, BPF_MAP_TYPE_SOCKHASH);
+	__uint(max_entries, 1);
+	__type(key, int);
+	__type(value, int);
+} sockhash SEC(".maps");
+
+struct {
+	__uint(type, BPF_MAP_TYPE_SOCKMAP);
+	__uint(max_entries, 1);
+	__type(key, int);
+	__type(value, int);
+} sockmap SEC(".maps");
+
+enum { CG_OK = 1 };
+
+int zero = 0;
+
+static __always_inline void test_sockmap_delete(void)
+{
+	bpf_map_delete_elem(&sockmap, &zero);
+	bpf_map_delete_elem(&sockhash, &zero);
+}
+
+static __always_inline void test_sockmap_update(void *sk)
+{
+	if (sk) {
+		bpf_map_update_elem(&sockmap, &zero, sk, BPF_ANY);
+		bpf_map_update_elem(&sockhash, &zero, sk, BPF_ANY);
+	}
+}
+
+static __always_inline void test_sockmap_lookup_and_update(void)
+{
+	struct bpf_sock *sk = bpf_map_lookup_elem(&sockmap, &zero);
+
+	if (sk) {
+		test_sockmap_update(sk);
+		bpf_sk_release(sk);
+	}
+}
+
+static __always_inline void test_sockmap_mutate(void *sk)
+{
+	test_sockmap_delete();
+	test_sockmap_update(sk);
+}
+
+static __always_inline void test_sockmap_lookup_and_mutate(void)
+{
+	test_sockmap_delete();
+	test_sockmap_lookup_and_update();
+}
+
+SEC("action")
+__success
+int test_sched_act(struct __sk_buff *skb)
+{
+	test_sockmap_mutate(skb->sk);
+	return 0;
+}
+
+SEC("classifier")
+__success
+int test_sched_cls(struct __sk_buff *skb)
+{
+	test_sockmap_mutate(skb->sk);
+	return 0;
+}
+
+SEC("flow_dissector")
+__success
+int test_flow_dissector_delete(struct __sk_buff *skb __always_unused)
+{
+	test_sockmap_delete();
+	return 0;
+}
+
+SEC("flow_dissector")
+__failure __msg("program of this type cannot use helper bpf_sk_release")
+int test_flow_dissector_update(struct __sk_buff *skb __always_unused)
+{
+	test_sockmap_lookup_and_update(); /* no access to skb->sk */
+	return 0;
+}
+
+SEC("iter/sockmap")
+__success
+int test_trace_iter(struct bpf_iter__sockmap *ctx)
+{
+	test_sockmap_mutate(ctx->sk);
+	return 0;
+}
+
+SEC("raw_tp/kfree")
+__failure __msg("cannot update sockmap in this context")
+int test_raw_tp_delete(const void *ctx __always_unused)
+{
+	test_sockmap_delete();
+	return 0;
+}
+
+SEC("raw_tp/kfree")
+__failure __msg("cannot update sockmap in this context")
+int test_raw_tp_update(const void *ctx __always_unused)
+{
+	test_sockmap_lookup_and_update();
+	return 0;
+}
+
+SEC("sk_lookup")
+__success
+int test_sk_lookup(struct bpf_sk_lookup *ctx)
+{
+	test_sockmap_mutate(ctx->sk);
+	return 0;
+}
+
+SEC("sk_reuseport")
+__success
+int test_sk_reuseport(struct sk_reuseport_md *ctx)
+{
+	test_sockmap_mutate(ctx->sk);
+	return 0;
+}
+
+SEC("socket")
+__success
+int test_socket_filter(struct __sk_buff *skb)
+{
+	test_sockmap_mutate(skb->sk);
+	return 0;
+}
+
+SEC("sockops")
+__success
+int test_sockops_delete(struct bpf_sock_ops *ctx __always_unused)
+{
+	test_sockmap_delete();
+	return CG_OK;
+}
+
+SEC("sockops")
+__failure __msg("cannot update sockmap in this context")
+int test_sockops_update(struct bpf_sock_ops *ctx)
+{
+	test_sockmap_update(ctx->sk);
+	return CG_OK;
+}
+
+SEC("sockops")
+__success
+int test_sockops_update_dedicated(struct bpf_sock_ops *ctx)
+{
+	bpf_sock_map_update(ctx, &sockmap, &zero, BPF_ANY);
+	bpf_sock_hash_update(ctx, &sockhash, &zero, BPF_ANY);
+	return CG_OK;
+}
+
+SEC("xdp")
+__success
+int test_xdp(struct xdp_md *ctx __always_unused)
+{
+	test_sockmap_lookup_and_mutate();
+	return XDP_PASS;
+}