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

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Date: Mon, 29 Apr 2024 16:30:46 -0700
From: Andy Lutomirski <luto@...capital.net>
To: Jiri Olsa <olsajiri@...il.com>
Cc: Ingo Molnar <mingo@...nel.org>, Linus Torvalds <torvalds@...ux-foundation.org>, 
	Hillf Danton <hdanton@...a.com>, Peter Anvin <hpa@...or.com>, Adrian Bunk <bunk@...nel.org>, 
	syzbot <syzbot+83e7f982ca045ab4405c@...kaller.appspotmail.com>, 
	Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>, andrii@...nel.org, bpf@...r.kernel.org, 
	linux-kernel@...r.kernel.org, syzkaller-bugs@...glegroups.com
Subject: Re: [PATCH] x86/mm: Remove broken vsyscall emulation code from the
 page fault code

On Mon, Apr 29, 2024 at 6:51 AM Jiri Olsa <olsajiri@...il.com> wrote:
>
> On Mon, Apr 29, 2024 at 10:00:51AM +0200, Ingo Molnar wrote:
>
> SNIP
>
> > 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.
> >
> > Not-Yet-Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
> > Signed-off-by: Ingo Molnar <mingo@...nel.org>
> > Link: https://lore.kernel.org/r/CAHk-=wh9D6f7HUkDgZHKmDCHUQmp+Co89GP+b8+z+G56BKeyNg@mail.gmail.com
>
> fwiw I can no longer trigger the invalid wait context bug
> with this change
>
> Tested-by: Jiri Olsa <jolsa@...nel.org>

Acked-by: Andy Lutomirski <luto@...nel.org>