linux-kernel - Re: [PATCH] bpf: add missing _

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAADnVQKn4xP9s_koBuP7D_eqUX0dSPwUr-dOj3mTZNTh_VxqKQ@mail.gmail.com>
Date: Tue, 3 Feb 2026 09:24:40 -0800
From: Alexei Starovoitov <alexei.starovoitov@...il.com>
To: Arnd Bergmann <arnd@...db.de>
Cc: Arnd Bergmann <arnd@...nel.org>, Alexei Starovoitov <ast@...nel.org>, 
	Daniel Borkmann <daniel@...earbox.net>, Andrii Nakryiko <andrii@...nel.org>, Song Liu <song@...nel.org>, 
	KP Singh <kpsingh@...nel.org>, Matt Bobrowski <mattbobrowski@...gle.com>, 
	Steven Rostedt <rostedt@...dmis.org>, Masami Hiramatsu <mhiramat@...nel.org>, 
	Martin KaFai Lau <martin.lau@...ux.dev>, Eduard Zingerman <eddyz87@...il.com>, 
	Yonghong Song <yonghong.song@...ux.dev>, John Fastabend <john.fastabend@...il.com>, 
	Stanislav Fomichev <sdf@...ichev.me>, Hao Luo <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>, 
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>, Mykyta Yatsenko <yatsenko@...a.com>, 
	Kumar Kartikeya Dwivedi <memxor@...il.com>, bpf <bpf@...r.kernel.org>, 
	LKML <linux-kernel@...r.kernel.org>, 
	linux-trace-kernel <linux-trace-kernel@...r.kernel.org>
Subject: Re: [PATCH] bpf: add missing __printf attributes

On Tue, Feb 3, 2026 at 8:58 AM Arnd Bergmann <arnd@...db.de> wrote:
>
> On Tue, Feb 3, 2026, at 17:34, Alexei Starovoitov wrote:
> > On Tue, Feb 3, 2026 at 8:27 AM Arnd Bergmann <arnd@...nel.org> wrote:
> >>
> >> From: Arnd Bergmann <arnd@...db.de>
> >>
> >> Some internal functions in bpf produce a warning when -Wsuggest-attribute=format
> >> is passed to the compiler, e.g. in 'make W=1':
> >>
> >> kernel/trace/bpf_trace.c: In function '____bpf_trace_printk':
> >> kernel/trace/bpf_trace.c:377:9: error: function '____bpf_trace_printk' might be a candidate for 'gnu_printf' format attribute [-Werror=suggest-attribute=format]
> >>   377 |         ret = bstr_printf(data.buf, MAX_BPRINTF_BUF, fmt, data.bin_args);
> >>       |         ^~~
> >>
> >> The attribute here is useless since there are no callers from C code,
> >> but it helps to shut up the output anyway so we can eventually turn
> >> the warning option on by default.
> >>
> >> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> >
> > This was discussed and it's incorrect.
>
> Do you have a reference to why it's incorrect?  It seems harmless
> and gives me a clean kernel build in combination with a handful
> of other fixes after enabling the option by default, but I assume
> I'm missing something,

because it's not a printf format. There are no varags here.
gnu_printf attribute takes two arguments:
format (archetype, string-index, first-to-check)
Also
"GCC requires a function with the 'format' attribute to be variadic"

> > Commit 7bf819aa992f ("vsnprintf: Mark binary printing functions with
> > __printf() attribute") should be reverted instead.
>
> Reverting that one would appear to introduce warnings elsewhere,
> so that would not be a complete fix either.

Somebody needs to root cause it and fix it properly.
Adding more incorrect annotation is not a solution.