netdev - [PATCH 1/2] selftests/bpf: Avoid errno clobbering

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Message-Id: <20201128192502.88195-2-dev@der-flo.net>
Date:   Sat, 28 Nov 2020 20:25:01 +0100
From:   Florian Lehner <dev@...-flo.net>
To:     bpf@...r.kernel.org
Cc:     netdev@...r.kernel.org, ast@...nel.org, daniel@...earbox.net,
        andrii@...nel.org, john.fastabend@...il.com,
        Florian Lehner <dev@...-flo.net>,
        Stanislav Fomichev <sdf@...gle.com>,
        Krzesimir Nowak <krzesimir@...volk.io>
Subject: [PATCH 1/2] selftests/bpf: Avoid errno clobbering

Commit 8184d44c9a57 ("selftests/bpf: skip verifier tests for unsupported
program types") added a check to skip unsupported program types. As
bpf_probe_prog_type can change errno, do_single_test should save it before
printing a reason why a supported BPF program type failed to load.

Fixes: 8184d44c9a57 ("selftests/bpf: skip verifier tests for unsupported program types")
Cc: Stanislav Fomichev <sdf@...gle.com>
Cc: Krzesimir Nowak <krzesimir@...volk.io>
Signed-off-by: Florian Lehner <dev@...-flo.net>
---
 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 4bfe3aa2cfc4..ceea9409639e 100644
--- a/tools/testing/selftests/bpf/test_verifier.c
+++ b/tools/testing/selftests/bpf/test_verifier.c
@@ -936,6 +936,7 @@ 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;
 	__u32 pflags;
 	int i, err;
@@ -997,6 +998,7 @@ static void do_test_single(struct bpf_test *test, bool unpriv,
 	}
 
 	fd_prog = bpf_load_program_xattr(&attr, bpf_vlog, sizeof(bpf_vlog));
+	saved_errno = errno;
 
 	/* BPF_PROG_TYPE_TRACING requires more setup and
 	 * bpf_probe_prog_type won't give correct answer
@@ -1013,7 +1015,7 @@ static void do_test_single(struct bpf_test *test, bool unpriv,
 	if (expected_ret == ACCEPT || expected_ret == VERBOSE_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
-- 
2.28.0