linux-kernel - [bpf-next v3 02/12] selftests/bpf: Avoid a clobbering of errno

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Message-Id: <20190708163121.18477-3-krzesimir@kinvolk.io>
Date:   Mon,  8 Jul 2019 18:31:11 +0200
From:   Krzesimir Nowak <krzesimir@...volk.io>
To:     linux-kernel@...r.kernel.org
Cc:     Alban Crequy <alban@...volk.io>,
        Iago López Galeiras <iago@...volk.io>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <jakub.kicinski@...ronome.com>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        John Fastabend <john.fastabend@...il.com>,
        Stanislav Fomichev <sdf@...gle.com>, netdev@...r.kernel.org,
        bpf@...r.kernel.org, xdp-newbies@...r.kernel.org,
        Krzesimir Nowak <krzesimir@...volk.io>
Subject: [bpf-next v3 02/12] 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.

Changes since v1:
- Fix the "Fixes:" tag to mention actual commit that introduced the
  bug

Changes since v2:
- Move the declaration so it fits the reverse christmas tree style.

Cc: Daniel Borkmann <daniel@...earbox.net>
Fixes: 832c6f2c29ec ("bpf: test make sure to run unpriv test cases in test_verifier")
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 b8d065623ead..3fe126e0083b 100644
--- a/tools/testing/selftests/bpf/test_verifier.c
+++ b/tools/testing/selftests/bpf/test_verifier.c
@@ -823,16 +823,18 @@ static int do_prog_test_run(int fd_prog, bool unpriv, uint32_t expected_val,
 	__u8 tmp[TEST_DATA_LEN << 2];
 	__u32 size_tmp = sizeof(tmp);
 	uint32_t retval;
+	int saved_errno;
 	int err;
 
 	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