linux-kernel - Re: [PATCH 24/30] x86, kaiser: disable native VSYSCALL

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: <CALCETrVoud2iVxAky5UGQkyiDgNiN7Zc-LfahG_1P-x3JQzopg@mail.gmail.com>
Date:   Fri, 10 Nov 2017 14:06:19 -0800
From:   Andy Lutomirski <luto@...nel.org>
To:     Dave Hansen <dave.hansen@...ux.intel.com>
Cc:     Andy Lutomirski <luto@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        moritz.lipp@...k.tugraz.at,
        Daniel Gruss <daniel.gruss@...k.tugraz.at>,
        michael.schwarz@...k.tugraz.at, richard.fellner@...dent.tugraz.at,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Kees Cook <keescook@...gle.com>,
        Hugh Dickins <hughd@...gle.com>, X86 ML <x86@...nel.org>
Subject: Re: [PATCH 24/30] x86, kaiser: disable native VSYSCALL

On Thu, Nov 9, 2017 at 10:31 PM, Dave Hansen
<dave.hansen@...ux.intel.com> wrote:
> On 11/09/2017 06:25 PM, Andy Lutomirski wrote:
>> Here are two proposals to address this without breaking vsyscalls.
>>
>> 1. Set NX on low mappings that are _PAGE_USER.  Don't set NX on high
>> mappings but, optionally, warn if you see _PAGE_USER on any address
>> that isn't the vsyscall page.
>>
>> 2. Ignore _PAGE_USER entirely and just mark the EFI mm as special so
>> KAISER doesn't muck with it.
>
> These are totally doable.  But, what's the big deal with breaking native
> vsyscall?  We can still do the emulation so nothing breaks: it is just slow.

I have nothing against disabling native.  I object to breaking the
weird binary tracing behavior in the emulation mode, especially if
it's tangled up with KAISER.  I got all kinds of flak in an earlier
version of the vsyscall emulation patches when I broke that use case.
KAISER may get very widely backported -- let's not make changes that
are already known to break things.