linux-hardening - Re: [PATCH] usercopy: delete __noreturn from usercopy

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Message-ID: <202403040938.D770633@keescook>
Date: Mon, 4 Mar 2024 09:40:01 -0800
From: Kees Cook <keescook@...omium.org>
To: Jann Horn <jannh@...gle.com>
Cc: Jiangfeng Xiao <xiaojiangfeng@...wei.com>, gustavoars@...nel.org,
	akpm@...ux-foundation.org, jpoimboe@...nel.org,
	peterz@...radead.org, dave.hansen@...ux.intel.com,
	kirill.shutemov@...ux.intel.com, linux-kernel@...r.kernel.org,
	linux-hardening@...r.kernel.org, linux-mm@...ck.org,
	nixiaoming@...wei.com, kepler.chenxin@...wei.com,
	wangbing6@...wei.com, wangfangpeng1@...wei.com,
	douzhaolei@...wei.com
Subject: Re: [PATCH] usercopy: delete __noreturn from usercopy_abort

On Mon, Mar 04, 2024 at 04:15:07PM +0100, Jann Horn wrote:
> On Mon, Mar 4, 2024 at 3:02 AM Jiangfeng Xiao <xiaojiangfeng@...wei.com> wrote:
> > When the last instruction of a noreturn function is a call
> > to another function, the return address falls outside
> > of the function boundary. This seems to cause kernel
> > to interrupt the backtrace.

FWIW, all email from huawei.com continues to get eaten by anti-spam
checking. I've reported this a few times -- it'd be really nice if the
domain configuration could get fixed.

> [...]
> > Delete __noreturn from usercopy_abort,
> 
> This sounds like the actual bug is in the backtracing logic? I don't
> think removing __noreturn annotations from an individual function is a
> good fix, since the same thing can happen with other __noreturn
> functions depending on what choices the compiler makes.

Yeah, NAK. usercopy_abort() doesn't return. It ends with BUG().

-- 
Kees Cook