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

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Message-ID: <Z9lAj-1COhR82P_O@krava>
Date: Tue, 18 Mar 2025 10:44:47 +0100
From: Jiri Olsa <olsajiri@...il.com>
To: Björn Töpel <bjorn@...nel.org>
Cc: Andrii Nakryiko <andrii@...nel.org>,
	Eduard Zingerman <eddyz87@...il.com>,
	Mykola Lysenko <mykolal@...com>, bpf@...r.kernel.org,
	Björn Töpel <bjorn@...osinc.com>,
	linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH bpf-next] selftests/bpf: Sanitize pointer prior fclose()

On Tue, Mar 18, 2025 at 09:16:47AM +0100, Björn Töpel wrote:
> 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>

Acked-by: Jiri Olsa <jolsa@...nel.org>

jirka

> ---
>  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;

nit, setting to NULL could be inside the condition

>  		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
> 
>