Messages in this thread | | | From | Andrii Nakryiko <> | Date | Tue, 13 Apr 2021 16:21:42 -0700 | Subject | Re: [PATCH bpf-next v3 6/6] selftests/bpf: Add a series of tests for bpf_snprintf |
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On Mon, Apr 12, 2021 at 8:38 AM Florent Revest <revest@chromium.org> wrote: > > This exercises most of the format specifiers. > > Signed-off-by: Florent Revest <revest@chromium.org> > Acked-by: Andrii Nakryiko <andrii@kernel.org> > ---
As I mentioned on another patch, we probably need negative tests even more than positive ones.
I think an easy and nice way to do this is to have a separate BPF skeleton where fmt string and arguments are provided through read-only global variables, so that user-space can re-use the same BPF skeleton to simulate multiple cases. BPF program itself would just call bpf_snprintf() and store the returned result.
Whether we need to validate the verifier log is up to debate (though it's not that hard to do by overriding libbpf_print_fn() callback), I'd be ok at least knowing that some bad format strings are rejected and don't crash the kernel.
> .../selftests/bpf/prog_tests/snprintf.c | 81 +++++++++++++++++++ > .../selftests/bpf/progs/test_snprintf.c | 74 +++++++++++++++++ > 2 files changed, 155 insertions(+) > create mode 100644 tools/testing/selftests/bpf/prog_tests/snprintf.c > create mode 100644 tools/testing/selftests/bpf/progs/test_snprintf.c >
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