linux-kernel - Re: [PATCH AUTOSEL 6.1 19/25] x86/mm: Remove broken vsyscall emulation code from the page fault code

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Date: Mon, 13 May 2024 10:22:51 +0200
From: Pavel Machek <pavel@...x.de>
To: Sasha Levin <sashal@...nel.org>
Cc: linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	syzbot+83e7f982ca045ab4405c@...kaller.appspotmail.com,
	Ingo Molnar <mingo@...nel.org>, Jiri Olsa <jolsa@...nel.org>,
	Andy Lutomirski <luto@...nel.org>, tglx@...utronix.de,
	mingo@...hat.com, bp@...en8.de, dave.hansen@...ux.intel.com,
	x86@...nel.org, peterz@...radead.org, xin3.li@...el.com,
	ubizjak@...il.com, rick.p.edgecombe@...el.com, arnd@...db.de,
	mjguzik@...il.com, bpf@...r.kernel.org
Subject: Re: [PATCH AUTOSEL 6.1 19/25] x86/mm: Remove broken vsyscall
 emulation code from the page fault code

Hi!

> From: Linus Torvalds <torvalds@...ux-foundation.org>
> 
> [ Upstream commit 02b670c1f88e78f42a6c5aee155c7b26960ca054 ]
...
> IOW, I think the only right thing is to remove that horrendously broken
> code.
> 
> The attached patch looks like the ObviouslyCorrect(tm) thing to do.
> 
> NOTE! This broken code goes back to this commit in 2011:
> 
>   4fc3490114bb ("x86-64: Set siginfo and context on vsyscall emulation faults")
> 
> .. and back then the reason was to get all the siginfo details right.
> Honestly, I do not for a moment believe that it's worth getting the siginfo
> details right here, but part of the commit says:
> 
>     This fixes issues with UML when vsyscall=emulate.
> 
> .. and so my patch to remove this garbage will probably break UML in this
> situation.
> 
> I do not believe that anybody should be running with vsyscall=emulate in
> 2024 in the first place, much less if you are doing things like UML. But
> let's see if somebody screams.

Surely this should not go to stable with just 14days in mainline? We
don't want stable users to scream.

Best regards,
								Pavel
-- 
DENX Software Engineering GmbH,        Managing Director: Erika Unter
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany

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