Re: [bpf-next v3 03/12] selftests/bpf: Avoid another case of errno clobbering

From: Krzesimir Nowak <krzesimir@kinvolk.io>
To: Andrii Nakryiko <andrii.nakryiko@gmail.com>
Cc: "open list" <linux-kernel@vger.kernel.org>,
	"Alban Crequy" <alban@kinvolk.io>,
	"Iago López Galeiras" <iago@kinvolk.io>,
	"Alexei Starovoitov" <ast@kernel.org>,
	"Daniel Borkmann" <daniel@iogearbox.net>,
	"Martin KaFai Lau" <kafai@fb.com>,
	"Song Liu" <songliubraving@fb.com>, "Yonghong Song" <yhs@fb.com>,
	"David S. Miller" <davem@davemloft.net>,
	"Jakub Kicinski" <jakub.kicinski@netronome.com>,
	"Jesper Dangaard Brouer" <hawk@kernel.org>,
	"John Fastabend" <john.fastabend@gmail.com>,
	"Stanislav Fomichev" <sdf@google.com>,
	Networking <netdev@vger.kernel.org>, bpf <bpf@vger.kernel.org>,
	xdp-newbies@vger.kernel.org
Subject: Re: [bpf-next v3 03/12] selftests/bpf: Avoid another case of errno clobbering
Date: Thu, 11 Jul 2019 14:05:11 +0200	[thread overview]
Message-ID: <CAGGp+cHi0siwc1+q--JM_+a0QOO6tWgJiOkqsdbjGxjMP3G1Zw@mail.gmail.com> (raw)
In-Reply-To: <CAEf4BzbM6EiCkN5mwK1YP-NC2bavkkHV7nFR-PXCWGOvVt7nTg@mail.gmail.com>

On Thu, Jul 11, 2019 at 1:57 AM Andrii Nakryiko
<andrii.nakryiko@gmail.com> wrote:
>
> On Mon, Jul 8, 2019 at 3:43 PM Krzesimir Nowak <krzesimir@kinvolk.io> wrote:
> >
> > Commit 8184d44c9a57 ("selftests/bpf: skip verifier tests for
> > unsupported program types") added a check for an unsupported program
> > type. The function doing it changes errno, so test_verifier should
> > save it before calling it if test_verifier wants to print a reason why
> > verifying a BPF program of a supported type failed.
> >
> > Changes since v2:
> > - Move the declaration to fit the reverse christmas tree style.
> >
> > Fixes: 8184d44c9a57 ("selftests/bpf: skip verifier tests for unsupported program types")
> > Cc: Stanislav Fomichev <sdf@google.com>
> > Signed-off-by: Krzesimir Nowak <krzesimir@kinvolk.io>
> > ---
>
> Acked-by: Andrii Nakryiko <andriin@fb.com>
>
> >  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 3fe126e0083b..c7541f572932 100644
> > --- a/tools/testing/selftests/bpf/test_verifier.c
> > +++ b/tools/testing/selftests/bpf/test_verifier.c
> > @@ -864,6 +864,7 @@ static void do_test_single(struct bpf_test *test, bool unpriv,
> >         int run_errs, run_successes;
> >         int map_fds[MAX_NR_MAPS];
> >         const char *expected_err;
> > +       int saved_errno;
> >         int fixup_skips;
>
> nit: combine those ints? or even with i and err below as well?

Will do.

>
> >         __u32 pflags;
> >         int i, err;
> > @@ -894,6 +895,7 @@ static void do_test_single(struct bpf_test *test, bool unpriv,
> >                 pflags |= BPF_F_ANY_ALIGNMENT;
> >         fd_prog = bpf_verify_program(prog_type, prog, prog_len, pflags,
> >                                      "GPL", 0, bpf_vlog, sizeof(bpf_vlog), 4);
> > +       saved_errno = errno;
> >         if (fd_prog < 0 && !bpf_probe_prog_type(prog_type, 0)) {
> >                 printf("SKIP (unsupported program type %d)\n", prog_type);
> >                 skips++;
> > @@ -910,7 +912,7 @@ static void do_test_single(struct bpf_test *test, bool unpriv,
> >         if (expected_ret == ACCEPT) {
> >                 if (fd_prog < 0) {
> >                         printf("FAIL\nFailed to load prog '%s'!\n",
> > -                              strerror(errno));
> > +                              strerror(saved_errno));
> >                         goto fail_log;
> >                 }
> >  #ifndef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
> > --
> > 2.20.1
> >

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