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Date: Mon, 13 Jan 2025 20:13:51 -0800
From: Andrew Morton <akpm@linux-foundation.org>
To: liuye <liuye@kylinos.cn>
Cc: shuah@kernel.org, jeffxu@google.com, isaacmanjarres@google.com,
 lorenzo.stoakes@oracle.com, gthelen@google.com, sauravshah.31@gmail.com,
 linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] selftests/memfd/memfd_test: Fix possible NULL pointer
 dereference
Message-Id: <20250113201351.3f48cc86f06a7dc01d497872@linux-foundation.org>
In-Reply-To: <20250114032115.58638-1-liuye@kylinos.cn>
References: <20250114032115.58638-1-liuye@kylinos.cn>
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On Tue, 14 Jan 2025 11:21:15 +0800 liuye <liuye@kylinos.cn> wrote:

>     If name is NULL, a NULL pointer may be accessed in printf.
> 
> ...
>
> --- a/tools/testing/selftests/memfd/memfd_test.c
> +++ b/tools/testing/selftests/memfd/memfd_test.c
> @@ -171,7 +171,7 @@ static void mfd_fail_new(const char *name, unsigned int flags)
>  	r = sys_memfd_create(name, flags);
>  	if (r >= 0) {
>  		printf("memfd_create(\"%s\", %u) succeeded, but failure expected\n",
> -		       name, flags);
> +		       name ? name : "NULL", flags);
>  		close(r);
>  		abort();

Well huh.  I though printf() would emit "(null)" in this situation, but
my super-sophisticated test case says "core dumped".

#include <stdio.h>
#include <stdlib.h>

int main()
{
	printf("%s\n", (char *)0);
	exit(0);
}