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>

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 20ddff6812e986654c7658788a371e1ea738554d..2e0ddef77ba51140b8e5cf10d186b9cc6f96dfff 100644 (file)
--- 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 (file)
index 0000000..932e1d9
--- /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";