linux-kernel - [PATCH bpf-next] selftests/bpf: Sanitize pointer prior fclose()

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Message-ID: <20250318081648.122523-1-bjorn@kernel.org>
Date: Tue, 18 Mar 2025 09:16:47 +0100
From: Björn Töpel <bjorn@...nel.org>
To: Andrii Nakryiko <andrii@...nel.org>,
	Eduard Zingerman <eddyz87@...il.com>,
	Mykola Lysenko <mykolal@...com>,
	bpf@...r.kernel.org
Cc: Björn Töpel <bjorn@...osinc.com>,
	linux-kselftest@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH bpf-next] selftests/bpf: Sanitize pointer prior fclose()

From: Björn Töpel <bjorn@...osinc.com>

There are scenarios where env.{sub,}test_state->stdout_saved, can be
NULL, e.g. sometimes when the watchdog timeout kicks in, or if the
open_memstream syscall is not available.

Avoid crashing test_progs by adding an explicit NULL check prior the
fclose() call.

Signed-off-by: Björn Töpel <bjorn@...osinc.com>
---
 tools/testing/selftests/bpf/test_progs.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/bpf/test_progs.c b/tools/testing/selftests/bpf/test_progs.c
index d4ec9586b98c..309d9d4a8ace 100644
--- a/tools/testing/selftests/bpf/test_progs.c
+++ b/tools/testing/selftests/bpf/test_progs.c
@@ -103,12 +103,14 @@ static void stdio_restore(void)
 	pthread_mutex_lock(&stdout_lock);
 
 	if (env.subtest_state) {
-		fclose(env.subtest_state->stdout_saved);
+		if (env.subtest_state->stdout_saved)
+			fclose(env.subtest_state->stdout_saved);
 		env.subtest_state->stdout_saved = NULL;
 		stdout = env.test_state->stdout_saved;
 		stderr = env.test_state->stdout_saved;
 	} else {
-		fclose(env.test_state->stdout_saved);
+		if (env.test_state->stdout_saved)
+			fclose(env.test_state->stdout_saved);
 		env.test_state->stdout_saved = NULL;
 		stdout = env.stdout_saved;
 		stderr = env.stderr_saved;

base-commit: f3f8649585a445414521a6d5b76f41b51205086d
-- 
2.45.2