linux-kernel - Re: [PATCH] vsnprintf: drop __printf() attributes on binary printing functions

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Message-ID: <aYW0RN2R_8zngExH@pathway.suse.cz>
Date: Fri, 6 Feb 2026 10:28:36 +0100
From: Petr Mladek <pmladek@...e.com>
To: Alexei Starovoitov <alexei.starovoitov@...il.com>
Cc: Arnd Bergmann <arnd@...db.de>, Arnd Bergmann <arnd@...nel.org>,
	Kees Cook <kees@...nel.org>,
	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
	kernel test robot <lkp@...el.com>,
	Andy Shevchenko <andy@...nel.org>,
	Alexei Starovoitov <ast@...nel.org>,
	Bartosz Golaszewski <brgl@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	linux-hardening@...r.kernel.org, bpf <bpf@...r.kernel.org>
Subject: Re: [PATCH] vsnprintf: drop __printf() attributes on binary printing
 functions

On Thu 2026-02-05 07:58:10, Alexei Starovoitov wrote:
> On Thu, Feb 5, 2026 at 2:13 AM Arnd Bergmann <arnd@...db.de> wrote:
> >
> > On Thu, Feb 5, 2026, at 09:53, Petr Mladek wrote:
> > > On Wed 2026-02-04 14:26:23, Arnd Bergmann wrote:
> > >> Fixes: 6b2c1e30ad68 ("seq_file: Mark binary printing functions with __printf() attribute")
> > >> Fixes: 7bf819aa992f ("vsnprintf: Mark binary printing functions with __printf() attribute")
> > >
> > > From the commit message, it is not obvious why reverting these commits
> > > won't bring back the warnings in the modified functions.
> > >
> > > My understanding is that the warnings won't get back thanks to
> > > the commit bd67c1c3c353b6560 ("vsnprintf: Silence false positive
> > > GCC warning for va_format()") as explained by the original cover
> > > letter, see
> > > https://lore.kernel.org/all/20250321144822.324050-1-andriy.shevchenko@linux.intel.com/#t
> > >
> > > It would be worth to mentionin this in the commit message.
> >
> > Unfortunately, I have not been able to reproduce the original
> > warnings at all. The va_format() warning and the patch to
> > silence that look entirely unrelated here, that was just the
> > compiler incorrectly identifying a function that does not even
> > take a format argument.
> >
> > I'm sure some other intermediate change managed to shut up
> > the warnings, but I don't know which one. My best guess would
> > be that 938df695e98d ("vsprintf: associate the format state with
> > the format pointer") made gcc no longer warn about bstr_printf(),
> > but that predates Andy's patch and I can't easily revert it for
> > testing. Checking out a kernel before those patches does have
> > the warning on va_format() but not on the other ones.

OK. The commit will include link to this thread. It should be good
enough ;-)

> > > I wonder who should take this patch. Should it go via
> > > printk/bpf/tracing or another tree?
> > > Does anyone has any preference, please?
> >
> > I think your tree makes most sense here, but I have no strong
> > preference.
> 
> As long as it makes into the upcoming merge window any tree is fine.
> Let's go via printk.

OK, I have committed the patch into printk/linux.git, branch for-6.20.

Best Regards,
Petr