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From: Andy Lutomirski <luto@amacapital.net>
Date: Mon, 29 Apr 2024 16:30:46 -0700
Message-ID: <CALCETrUUOU55ctJwxZeV7N-a_hadV7ejYnacEDbhmc5PFb0fvw@mail.gmail.com>
Subject: Re: [PATCH] x86/mm: Remove broken vsyscall emulation code from the
 page fault code
To: Jiri Olsa <olsajiri@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>, Linus Torvalds <torvalds@linux-foundation.org>, 
	Hillf Danton <hdanton@sina.com>, Peter Anvin <hpa@zytor.com>, Adrian Bunk <bunk@kernel.org>, 
	syzbot <syzbot+83e7f982ca045ab4405c@syzkaller.appspotmail.com>, 
	Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>, andrii@kernel.org, bpf@vger.kernel.org, 
	linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com
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On Mon, Apr 29, 2024 at 6:51=E2=80=AFAM Jiri Olsa <olsajiri@gmail.com> wrot=
e:
>
> 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 sig=
info
> > details right here, but part of the commit says:
> >
> >     This fixes issues with UML when vsyscall=3Demulate.
> >
> > ... and so my patch to remove this garbage will probably break UML in t=
his
> > situation.
> >
> > I do not believe that anybody should be running with vsyscall=3Demulate=
 in
> > 2024 in the first place, much less if you are doing things like UML. Bu=
t
> > let's see if somebody screams.
> >
> > Not-Yet-Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
> > Signed-off-by: Ingo Molnar <mingo@kernel.org>
> > Link: https://lore.kernel.org/r/CAHk-=3Dwh9D6f7HUkDgZHKmDCHUQmp+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@kernel.org>

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