From d80507d15d45e285fc596d23665c9b88cf0dfec3 Mon Sep 17 00:00:00 2001 From: Stanislav Fomichev Date: Fri, 30 Aug 2019 19:34:26 -0700 Subject: [PATCH] selftests/bpf: test_progs: fix verbose mode garbage fseeko(.., 0, SEEK_SET) on a memstream just puts the buffer pointer to the beginning so when we call fflush on it we get some garbage log data from the previous test. Let's manually set terminating byte to zero at the reported buffer size. To show the issue consider the following snippet: stream = open_memstream (&buf, &len); fprintf(stream, "aaa"); fflush(stream); printf("buf=%s, len=%zu\n", buf, len); fseeko(stream, 0, SEEK_SET); fprintf(stream, "b"); fflush(stream); printf("buf=%s, len=%zu\n", buf, len); Output: buf=aaa, len=3 buf=baa, len=1 Fixes: 946152b3c5d6 ("selftests/bpf: test_progs: switch to open_memstream") Signed-off-by: Stanislav Fomichev Signed-off-by: Daniel Borkmann --- tools/testing/selftests/bpf/test_progs.c | 1 + 1 file changed, 1 insertion(+) diff --git a/tools/testing/selftests/bpf/test_progs.c b/tools/testing/selftests/bpf/test_progs.c index e5892cb60eca..e8616e778cb5 100644 --- a/tools/testing/selftests/bpf/test_progs.c +++ b/tools/testing/selftests/bpf/test_progs.c @@ -45,6 +45,7 @@ static void dump_test_log(const struct prog_test_def *test, bool failed) if (env.verbose || test->force_log || failed) { if (env.log_cnt) { + env.log_buf[env.log_cnt] = '\0'; fprintf(env.stdout, "%s", env.log_buf); if (env.log_buf[env.log_cnt - 1] != '\n') fprintf(env.stdout, "\n"); -- 2.30.2