linux-kernel - Re: [PATCH -v2] x86/retpoline: Ensure default return thunk isn't used at runtime

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Message-ID: <20240104132623.GFZZax/wyf5Y3rMX5G@fat_crate.local>
Date: Thu, 4 Jan 2024 14:26:23 +0100
From: Borislav Petkov <bp@...en8.de>
To: Josh Poimboeuf <jpoimboe@...nel.org>
Cc: "Kaplan, David" <David.Kaplan@....com>, Ingo Molnar <mingo@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-tip-commits@...r.kernel.org" <linux-tip-commits@...r.kernel.org>,
	"Peter Zijlstra (Intel)" <peterz@...radead.org>,
	"x86@...nel.org" <x86@...nel.org>,
	David Howells <dhowells@...hat.com>
Subject: Re: [PATCH -v2] x86/retpoline: Ensure default return thunk isn't
 used at runtime

On Thu, Jan 04, 2024 at 02:24:46PM +0100, Borislav Petkov wrote:
> +void __warn_thunk(void)
> +{
> +	pr_warn_once("\n");
> +	pr_warn_once("**********************************************************\n");
> +	pr_warn_once("**   NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE   **\n");
> +	pr_warn_once("**                                                      **\n");
> +	pr_warn_once("**   Unpatched return thunk in use. This should not     **\n");
> +	pr_warn_once("**   happen on a production kernel. Please report this  **\n");
> +	pr_warn_once("**   to x86@...nel.org.                                 **\n");

I'm not yet sure here whether this should say "upstream kernels" because
otherwise we'll get a bunch of distro or whatnot downstream kernels
reports where we can't really do anything about...

Hmmm.

-- 
Regards/Gruss,
    Boris.

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