linux-kernel - Re: [PATCH 2/6] x86: Enable seccomp architecture tracking

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <202009240011.A56710DC@keescook>
Date:   Thu, 24 Sep 2020 00:12:19 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Jann Horn <jannh@...gle.com>
Cc:     YiFei Zhu <yifeifz2@...inois.edu>,
        Christian Brauner <christian.brauner@...ntu.com>,
        Tycho Andersen <tycho@...ho.pizza>,
        Andy Lutomirski <luto@...capital.net>,
        Will Drewry <wad@...omium.org>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Giuseppe Scrivano <gscrivan@...hat.com>,
        Tobin Feldman-Fitzthum <tobin@....com>,
        Dimitrios Skarlatos <dskarlat@...cmu.edu>,
        Valentin Rothberg <vrothber@...hat.com>,
        Hubertus Franke <frankeh@...ibm.com>,
        Jack Chen <jianyan2@...inois.edu>,
        Josep Torrellas <torrella@...inois.edu>,
        Tianyin Xu <tyxu@...inois.edu>, bpf <bpf@...r.kernel.org>,
        Linux Containers <containers@...ts.linux-foundation.org>,
        Linux API <linux-api@...r.kernel.org>,
        kernel list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/6] x86: Enable seccomp architecture tracking

On Thu, Sep 24, 2020 at 02:45:45AM +0200, Jann Horn wrote:
> On Thu, Sep 24, 2020 at 1:29 AM Kees Cook <keescook@...omium.org> wrote:
> > Provide seccomp internals with the details to calculate which syscall
> > table the running kernel is expecting to deal with. This allows for
> > efficient architecture pinning and paves the way for constant-action
> > bitmaps.
> [...]
> > diff --git a/arch/x86/include/asm/seccomp.h b/arch/x86/include/asm/seccomp.h
> [...]
> > +#ifdef CONFIG_X86_64
> [...]
> > +#else /* !CONFIG_X86_64 */
> > +# define SECCOMP_ARCH                                  AUDIT_ARCH_I386
> > +#endif
> 
> If we are on a 32-bit kernel, performing architecture number checks in
> the kernel is completely pointless, because we know that there is only
> a single architecture identifier under which syscalls can happen.
> 
> While this patch is useful for enabling the bitmap logic in the
> following patches, I think it adds unnecessary overhead in the context
> of the previous patch.

That's what the RFC was trying to do (avoid the logic if there is only a
single arch known to the kernel). I will rework this a bit harder. :)

-- 
Kees Cook