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

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Date: Mon, 4 Mar 2024 16:15:07 +0100
From: Jann Horn <jannh@...gle.com>
To: Jiangfeng Xiao <xiaojiangfeng@...wei.com>
Cc: gustavoars@...nel.org, akpm@...ux-foundation.org, jpoimboe@...nel.org, 
	peterz@...radead.org, dave.hansen@...ux.intel.com, 
	kirill.shutemov@...ux.intel.com, keescook@...omium.org, 
	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 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.
[...]
> 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.