On Wed, 1 Apr 2026 at 21:11, Varun R Mallya <[email protected]> wrote: > > 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. > > Signed-off-by: Varun R Mallya <[email protected]> > ---
Acked-by: Kumar Kartikeya Dwivedi <[email protected]> > .../bpf/prog_tests/kprobe_multi_test.c | 41 +++++++++++++++++++ > .../bpf/progs/kprobe_multi_sleepable.c | 13 ++++++ > 2 files changed, 54 insertions(+) > create mode 100644 tools/testing/selftests/bpf/progs/kprobe_multi_sleepable.c > > 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 78c974d4ea33..f02fec2b6fda 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" > > @@ -633,6 +634,44 @@ static void test_attach_write_ctx(void) > } > #endif > > +static void test_attach_multi_sleepable(void) > +{ > + struct kprobe_multi_sleepable *skel; > + int err; > + > + skel = kprobe_multi_sleepable__open(); > + if (!ASSERT_OK_PTR(skel, "kprobe_multi_sleepable__open")) > + return; > + > + err = > bpf_program__set_flags(skel->progs.handle_kprobe_multi_sleepable, > + BPF_F_SLEEPABLE); > + if (!ASSERT_OK(err, "bpf_program__set_flags")) > + goto cleanup; > + > + /* Load should succeed even with BPF_F_SLEEPABLE for KPROBE types */ > + err = kprobe_multi_sleepable__load(skel); > + if (!ASSERT_OK(err, "kprobe_multi_sleepable__load")) > + goto cleanup; > + > + /* Attachment must fail for kprobe.multi + BPF_F_SLEEPABLE. > + * Also chosen a stable symbol to send into opts > + */ > + LIBBPF_OPTS(bpf_kprobe_multi_opts, opts); > + const char *sym = "vfs_read"; > + > + opts.syms = &sym; > + opts.cnt = 1; > + > + skel->links.handle_kprobe_multi_sleepable = > + > bpf_program__attach_kprobe_multi_opts(skel->progs.handle_kprobe_multi_sleepable, > + NULL, &opts); > + ASSERT_ERR_PTR(skel->links.handle_kprobe_multi_sleepable, > + "bpf_program__attach_kprobe_multi_opts"); Nit: While vfs_read will likely remain stable, the check could probably be stronger to distinguish an attach error from -EINVAL? I added a typo to vfs_read and it still passed, because it failed to attach instead of getting rejected on unfixed kernel. May not be a big deal since vfs_read is unlikely to break. I verified it works by adding bpf_copy_from_user to the program and attaching to SYS_PREFIX sys_getpid and invoking the splat though, so LGTM otherwise. > + > +cleanup: > + kprobe_multi_sleepable__destroy(skel); > +} > + > [...]
