selftests/bpf: Add test to ensure kprobe_multi is not sleepable

Add a selftest to ensure that kprobe_multi programs cannot be attached
using the BPF_F_SLEEPABLE flag. This test succeeds when the kernel
rejects attachment of kprobe_multi when the BPF_F_SLEEPABLE flag is set.

Suggested-by: Leon Hwang <leon.hwang@linux.dev>
Signed-off-by: Varun R Mallya <varunrmallya@gmail.com>
Link: https://lore.kernel.org/r/20260408190137.101418-3-varunrmallya@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

2 files changed, 59 insertions, 1 deletions

diff --git a/tools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c b/tools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c
index 20ddff6812e9..2e0ddef77ba5 100644
--- a/tools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c
+++ b/tools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c
@@ -10,6 +10,7 @@
 #include "kprobe_multi_session_cookie.skel.h"
 #include "kprobe_multi_verifier.skel.h"
 #include "kprobe_write_ctx.skel.h"
+#include "kprobe_multi_sleepable.skel.h"
 #include "bpf/libbpf_internal.h"
 #include "bpf/hashmap.h"
 
@@ -220,7 +221,9 @@ static void test_attach_api_syms(void)
 static void test_attach_api_fails(void)
 {
 	LIBBPF_OPTS(bpf_kprobe_multi_opts, opts);
+	LIBBPF_OPTS(bpf_test_run_opts, topts);
 	struct kprobe_multi *skel = NULL;
+	struct kprobe_multi_sleepable *sl_skel = NULL;
 	struct bpf_link *link = NULL;
 	unsigned long long addrs[2];
 	const char *syms[2] = {
@@ -228,7 +231,7 @@ static void test_attach_api_fails(void)
 		"bpf_fentry_test2",
 	};
 	__u64 cookies[2];
-	int saved_error;
+	int saved_error, err;
 
 	addrs[0] = ksym_get_addr("bpf_fentry_test1");
 	addrs[1] = ksym_get_addr("bpf_fentry_test2");
@@ -351,9 +354,39 @@ static void test_attach_api_fails(void)
 	if (!ASSERT_EQ(saved_error, -ENOENT, "fail_8_error"))
 		goto cleanup;
 
+	/* fail_9 - sleepable kprobe multi should not attach */
+	sl_skel = kprobe_multi_sleepable__open();
+	if (!ASSERT_OK_PTR(sl_skel, "sleep_skel_open"))
+		goto cleanup;
+
+	sl_skel->bss->user_ptr = sl_skel;
+
+	err = bpf_program__set_flags(sl_skel->progs.handle_kprobe_multi_sleepable,
+				     BPF_F_SLEEPABLE);
+	if (!ASSERT_OK(err, "sleep_skel_set_flags"))
+		goto cleanup;
+
+	err = kprobe_multi_sleepable__load(sl_skel);
+	if (!ASSERT_OK(err, "sleep_skel_load"))
+		goto cleanup;
+
+	link = bpf_program__attach_kprobe_multi_opts(sl_skel->progs.handle_kprobe_multi_sleepable,
+						     "bpf_fentry_test1", NULL);
+	saved_error = -errno;
+
+	if (!ASSERT_ERR_PTR(link, "fail_9"))
+		goto cleanup;
+
+	if (!ASSERT_EQ(saved_error, -EINVAL, "fail_9_error"))
+		goto cleanup;
+
+	err = bpf_prog_test_run_opts(bpf_program__fd(sl_skel->progs.fentry), &topts);
+	ASSERT_OK(err, "bpf_prog_test_run_opts");
+
 cleanup:
 	bpf_link__destroy(link);
 	kprobe_multi__destroy(skel);
+	kprobe_multi_sleepable__destroy(sl_skel);
 }
 
 static void test_session_skel_api(void)
diff --git a/tools/testing/selftests/bpf/progs/kprobe_multi_sleepable.c b/tools/testing/selftests/bpf/progs/kprobe_multi_sleepable.c
new file mode 100644
index 000000000000..932e1d9c72e2
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/kprobe_multi_sleepable.c
@@ -0,0 +1,25 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include "vmlinux.h"
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+
+void *user_ptr = 0;
+
+SEC("kprobe.multi")
+int handle_kprobe_multi_sleepable(struct pt_regs *ctx)
+{
+	int a, err;
+
+	err = bpf_copy_from_user(&a, sizeof(a), user_ptr);
+	barrier_var(a);
+	return err;
+}
+
+SEC("fentry/bpf_fentry_test1")
+int BPF_PROG(fentry)
+{
+	return 0;
+}
+
+char _license[] SEC("license") = "GPL";