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

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Date:   Wed, 15 May 2019 15:47:28 +0200
From:   Krzesimir Nowak <krzesimir@...volk.io>
To:     bpf@...r.kernel.org
Cc:     iago@...volk.io, alban@...volk.io,
        Krzesimir Nowak <krzesimir@...volk.io>,
        Jakub Kicinski <jakub.kicinski@...ronome.com>,
        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: [PATCH bpf v1 3/3] selftests/bpf: Avoid a clobbering of errno

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")
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;
-- 
2.20.1