linux-hardening - Re: [RFC PATCH 00/17] objtool: add base support for arm64

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: <c52dd4e2-2a9e-fdcd-1cca-4d6b237993b4@linux.microsoft.com>
Date:   Fri, 22 Jan 2021 15:44:35 -0600
From:   "Madhavan T. Venkataraman" <madvenka@...ux.microsoft.com>
To:     Ard Biesheuvel <ardb@...nel.org>
Cc:     Mark Brown <broonie@...nel.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Mark Rutland <mark.rutland@....com>,
        Michal Marek <michal.lkml@...kovi.net>,
        Julien Thierry <jthierry@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-efi <linux-efi@...r.kernel.org>,
        linux-hardening@...r.kernel.org, live-patching@...r.kernel.org,
        Will Deacon <will@...nel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Kees Cook <keescook@...omium.org>
Subject: Re: [RFC PATCH 00/17] objtool: add base support for arm64



On 1/22/21 3:43 PM, Ard Biesheuvel wrote:
> On Fri, 22 Jan 2021 at 22:15, Madhavan T. Venkataraman
> <madvenka@...ux.microsoft.com> wrote:
>>
>>
>>
>> On 1/22/21 11:43 AM, Mark Brown wrote:
>>> On Thu, Jan 21, 2021 at 12:54:52PM -0600, Josh Poimboeuf wrote:
>>>
>>>> 2) The shadow stack idea sounds promising -- how hard would it be to
>>>>    make a prototype reliable unwinder?
>>>
>>> In theory it doesn't look too hard and I can't see a particular reason
>>> not to try doing this - there's going to be edge cases but hopefully for
>>> reliable stack trace they're all in areas where we would be happy to
>>> just decide the stack isn't reliable anyway, things like nesting which
>>> allocates separate shadow stacks for each nested level for example.
>>> I'll take a look.
>>>
>>
>> I am a new comer to this discussion and I am learning. Just have some
>> questions. Pardon me if they are obvious or if they have already been
>> asked and answered.
>>
>> Doesn't Clang already have support for a shadow stack implementation for ARM64?
>> We could take a look at how Clang does it.
>>
>> Will there not be a significant performance hit? May be, some of it can be
>> mitigated by using a parallel shadow stack rather than a compact one.
>>
>> Are there any longjmp style situations in the kernel where the stack is
>> unwound by several frames? In these cases, the shadow stack must be unwound
>> accordingly.
>>
> 
> Hello Madhavan,
> 
> Let's discuss the details of shadow call stacks on a separate thread,
> instead of further hijacking Julien's series.
> 

OK. Sounds good.