linux-hardening - Re: [PATCH] x86/boot: add prototype for __fortify

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Message-ID: <20240531212009.GOZlo_CV0lxZ1xviQW@fat_crate.local>
Date: Fri, 31 May 2024 23:20:09 +0200
From: Borislav Petkov <bp@...en8.de>
To: Kees Cook <kees@...nel.org>
Cc: Jeff Johnson <quic_jjohnson@...cinc.com>,
	Nikolay Borisov <nik.borisov@...e.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
	"H. Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org,
	linux-hardening@...r.kernel.org, kernel-janitors@...r.kernel.org
Subject: Re: [PATCH] x86/boot: add prototype for __fortify_panic()

On Fri, May 31, 2024 at 02:06:48PM -0700, Kees Cook wrote:
> ...
> or refactors and forgets to change some name, etc. It's all for catching
> bugs before they happen, etc. And when source string lengths aren't
> known, the runtime checking can kick in too.

Aha, thanks for explaining.

> It happens x86 boot doesn't have any of those (good!) so
> __fortify_panic() goes unused there. But

Exactly!

> that's a larger topic covered by stuff like
> CONFIG_LD_DEAD_CODE_DATA_ELIMINATION, etc.

"... This option is not well tested yet, so use at your own risk."

Oh well.

So I get an allergic reaction everytime we wag the dog - i.e., fix the
code because some tool or option can't handle it even if it is
a perfectly fine code. In that case it is an unused symbol.

And frankly, I'd prefer the silly warning to denote that fortify doesn't
need to do any checking there vs shutting it up just because.

So can we aim our efforts at real bugs please?

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette