linux-kernel - Re: [PATCH v2] selftests/seccomp: fix pointer type mismatch in UPROBE test

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Message-ID: <aP8p0Td0LLa6Odit@krava>
Date: Mon, 27 Oct 2025 09:14:09 +0100
From: Jiri Olsa <olsajiri@...il.com>
To: Nirbhay Sharma <nirbhay.lkd@...il.com>
Cc: Kees Cook <kees@...nel.org>, Shuah Khan <shuah@...nel.org>,
	Andy Lutomirski <luto@...capital.net>,
	Will Drewry <wad@...omium.org>,
	Nathan Chancellor <nathan@...nel.org>,
	Nick Desaulniers <nick.desaulniers+lkml@...il.com>,
	Bill Wendling <morbo@...gle.com>,
	Justin Stitt <justinstitt@...gle.com>,
	linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org,
	bpf@...r.kernel.org, llvm@...ts.linux.dev, khalid@...nel.org,
	david.hunter.linux@...il.com,
	linux-kernel-mentees@...ts.linuxfoundation.org,
	Jiri Olsa <olsajiri@...il.com>, sam@...too.org
Subject: Re: [PATCH v2] selftests/seccomp: fix pointer type mismatch in
 UPROBE test

On Sun, Oct 26, 2025 at 02:42:33PM +0530, Nirbhay Sharma wrote:
> Fix compilation error in UPROBE_setup caused by pointer type mismatch
> in the ternary expression when compiled with -fcf-protection. The
> probed_uprobe function pointer has the __attribute__((nocf_check))
> attribute, which causes the conditional operator to fail when combined
> with the regular probed_uretprobe function pointer:
> 
>   seccomp_bpf.c:5175:74: error: pointer type mismatch in conditional
>   expression [-Wincompatible-pointer-types]
> 
> Cast both function pointers to 'const void *' to match the expected
> parameter type of get_uprobe_offset(), resolving the type mismatch
> while preserving the function selection logic.
> 
> This error appears with compilers that enable Control Flow Integrity
> (CFI) protection via -fcf-protection, such as Clang 19.1.2 (default
> on Fedora).
> 
> Signed-off-by: Nirbhay Sharma <nirbhay.lkd@...il.com>

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

thanks,
jirka

> ---
>  tools/testing/selftests/seccomp/seccomp_bpf.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/testing/selftests/seccomp/seccomp_bpf.c b/tools/testing/selftests/seccomp/seccomp_bpf.c
> index 874f17763536..e13ffe18ef95 100644
> --- a/tools/testing/selftests/seccomp/seccomp_bpf.c
> +++ b/tools/testing/selftests/seccomp/seccomp_bpf.c
> @@ -5172,7 +5172,8 @@ FIXTURE_SETUP(UPROBE)
>  		ASSERT_GE(bit, 0);
>  	}
>  
> -	offset = get_uprobe_offset(variant->uretprobe ? probed_uretprobe : probed_uprobe);
> +	offset = get_uprobe_offset(variant->uretprobe ?
> +		(const void *)probed_uretprobe : (const void *)probed_uprobe);
>  	ASSERT_GE(offset, 0);
>  
>  	if (variant->uretprobe)
> -- 
> 2.48.1
>