On Thu, 2 Apr 2026 at 11:46, Jiri Olsa <[email protected]> wrote: > > On Thu, Apr 02, 2026 at 12:50:10AM +0200, Kumar Kartikeya Dwivedi wrote: > > 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. > > why not use bpf_fentry_test2 ? you could also put it in pattern argument > and bypass opts completely (up to you) > > also there's test_attach_api_fails test, please move it over there >
Varun, the selftest is still not applied, only the fix. Please follow up and target bpf-next tree this time. Thanks.
