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

From: Jakub Kicinski
Date: Wed May 15 2019 - 17:52:56 EST


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@xxxxxxxxxxxxx>
> 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")

> Signed-off-by: Krzesimir Nowak <krzesimir@xxxxxxxxxx>
> ---
> 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;