linux-kernel - Re: [PATCH bpf v1 3/3] selftests/bpf: Avoid a clobbering of errno

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Message-ID: <CAGGp+cHqJZFfYt9VUAuQ7SpCZZ9ijoreKVBumc+wnGfw7pAXTA@mail.gmail.com>
Date:   Thu, 16 May 2019 11:31:04 +0200
From:   Krzesimir Nowak <krzesimir@...volk.io>
To:     Jakub Kicinski <jakub.kicinski@...ronome.com>
Cc:     bpf@...r.kernel.org,
        Iago López Galeiras <iago@...volk.io>,
        "Alban Crequy (Kinvolk)" <alban@...volk.io>,
        Shuah Khan <shuah@...nel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        Andrey Ignatov <rdna@...com>,
        Jiong Wang <jiong.wang@...ronome.com>,
        linux-kselftest@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH bpf v1 3/3] selftests/bpf: Avoid a clobbering of errno

On Wed, May 15, 2019 at 11:51 PM Jakub Kicinski
<jakub.kicinski@...ronome.com> wrote:
>
> On Wed, 15 May 2019 15:47:28 +0200, Krzesimir Nowak wrote:
> > Save errno right after bpf_prog_test_run returns, so we later check
> > the error code actually set by bpf_prog_test_run, not by some libcap
> > function.
> >
> > Cc: Jakub Kicinski <jakub.kicinski@...ronome.com>
> > Fixes: 5a8d5209ac022 ("selftests: bpf: add trivial JSET tests")
>
> This commit (of mine) just moved this code into a helper, the bug is
> older:
>
> Fixes: 832c6f2c29ec ("bpf: test make sure to run unpriv test cases in test_verifier")

Oops, ok. Will fix it. Thanks.

>
> > Signed-off-by: Krzesimir Nowak <krzesimir@...volk.io>
> > ---
> >  tools/testing/selftests/bpf/test_verifier.c | 4 +++-
> >  1 file changed, 3 insertions(+), 1 deletion(-)
> >
> > diff --git a/tools/testing/selftests/bpf/test_verifier.c b/tools/testing/selftests/bpf/test_verifier.c
> > index bf0da03f593b..514e17246396 100644
> > --- a/tools/testing/selftests/bpf/test_verifier.c
> > +++ b/tools/testing/selftests/bpf/test_verifier.c
> > @@ -818,15 +818,17 @@ static int do_prog_test_run(int fd_prog, bool unpriv, uint32_t expected_val,
> >       __u32 size_tmp = sizeof(tmp);
> >       uint32_t retval;
> >       int err;
> > +     int saved_errno;
> >
> >       if (unpriv)
> >               set_admin(true);
> >       err = bpf_prog_test_run(fd_prog, 1, data, size_data,
> >                               tmp, &size_tmp, &retval, NULL);
> > +     saved_errno = errno;
> >       if (unpriv)
> >               set_admin(false);
> >       if (err) {
> > -             switch (errno) {
> > +             switch (saved_errno) {
> >               case 524/*ENOTSUPP*/:
> >                       printf("Did not run the program (not supported) ");
> >                       return 0;
>


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