Re: [bpf-next v2 03/10] selftests/bpf: Avoid another case of errno clobbering

Stanislav Fomichev
2019-06-25T20:08:27Z

On 06/25, Krzesimir Nowak 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.
>
> 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>
> ---
> 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 12589da13487..779e30b96ded 100644
> --- a/tools/testing/selftests/bpf/test_verifier.c
> +++ b/tools/testing/selftests/bpf/test_verifier.c
> @@ -867,6 +867,7 @@ static void do_test_single(struct bpf_test *test, bool unpriv,
> int fixup_skips;
> __u32 pflags;
> int i, err;
> + int saved_errno;
Reverse Christmas tree. Otherwise LGTM.

>
> for (i = 0; i < MAX_NR_MAPS; i++)
> map_fds[i] = -1;
> @@ -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
>