linux-kernel - Re: [PATCH 6/8] x86: Provide API for local kernel TLB flushing

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Message-ID: <202006161136.524AA1C@keescook>
Date:   Tue, 16 Jun 2020 11:37:49 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Andy Lutomirski <luto@...nel.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Christian Brauner <christian@...uner.io>,
        Sargun Dhillon <sargun@...gun.me>,
        Tycho Andersen <tycho@...ho.ws>, Jann Horn <jannh@...gle.com>,
        "zhujianwei (C)" <zhujianwei7@...wei.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Matthew Wilcox <willy@...radead.org>,
        Will Drewry <wad@...omium.org>, Shuah Khan <shuah@...nel.org>,
        Matt Denton <mpdenton@...gle.com>,
        Chris Palmer <palmer@...gle.com>,
        Jeffrey Vander Stoep <jeffv@...gle.com>,
        Aleksa Sarai <cyphar@...har.com>,
        Hehuazhen <hehuazhen@...wei.com>, X86 ML <x86@...nel.org>,
        Linux Containers <containers@...ts.linux-foundation.org>,
        LSM List <linux-security-module@...r.kernel.org>,
        Linux API <linux-api@...r.kernel.org>
Subject: Re: [PATCH 6/8] x86: Provide API for local kernel TLB flushing

On Tue, Jun 16, 2020 at 09:59:29AM -0700, Andy Lutomirski wrote:
> On Tue, Jun 16, 2020 at 12:49 AM Kees Cook <keescook@...omium.org> wrote:
> >
> > The seccomp constant action bitmap filter evaluation routine depends
> > on being able to quickly clear the PTE "accessed" bit for a temporary
> > allocation. Provide access to the existing CPU-local kernel memory TLB
> > flushing routines.
> 
> Can you write a better justification?  Also, unless I'm just

Er, dunno? That's the entire reason this series needs it.

> incompetent this morning, I can't find anyone calling this in the
> series.

It's in patch 4, seccomp_update_bitmap():
https://lore.kernel.org/lkml/20200616074934.1600036-5-keescook@chromium.org/

-- 
Kees Cook