linux-kernel - Re: [PATCH v2 0/4] x86: fix get_nr_restart

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Message-ID: <CALCETrWJ8PLbxvX6yuP7Q3kz_=dZinacUd-3-OqUkZNSMCE34g@mail.gmail.com>
Date:   Wed, 18 Dec 2019 18:48:24 -0800
From:   Andy Lutomirski <luto@...nel.org>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Oleg Nesterov <oleg@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Andy Lutomirski <luto@...nel.org>,
        Borislav Petkov <bp@...en8.de>, Ingo Molnar <mingo@...nel.org>,
        Jan Kratochvil <jan.kratochvil@...hat.com>,
        Pedro Alves <palves@...hat.com>, Peter Anvin <hpa@...or.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "the arch/x86 maintainers" <x86@...nel.org>
Subject: Re: [PATCH v2 0/4] x86: fix get_nr_restart_syscall()

On Wed, Dec 18, 2019 at 12:02 PM Linus Torvalds
<torvalds@...ux-foundation.org> wrote:
>
> On Wed, Dec 18, 2019 at 7:19 AM Oleg Nesterov <oleg@...hat.com> wrote:
> >
> > Andy, Linus, do you have any objections?
>
> It's ok by me, no objections. I still don't love your "hide the bit in
> thread flags over return to user space", and would still prefer it in
> the restart block, but I don't care _that_ deeply.
>

I'd rather stick it in restart_block.  I'd also like to see the kernel
*verify* that the variant of restart_syscall() that's invoked is the
same as the variant that should be invoked.  In my mind, very few
syscalls say "I can't believe there are no major bugs in here" like
restart_syscall(), and being conservative is nice.