linux-kernel - Re: [PATCH] x86/entry/64: wipe KASAN stack shadow in rewind_stack_do

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: <daba9c5b-b5c6-beaa-ca96-81cf6af760b9@virtuozzo.com>
Date:   Tue, 28 Aug 2018 14:33:48 +0300
From:   Andrey Ryabinin <aryabinin@...tuozzo.com>
To:     Jann Horn <jannh@...gle.com>
Cc:     Andy Lutomirski <luto@...nel.org>,
        the arch/x86 maintainers <x86@...nel.org>,
        kernel list <linux-kernel@...r.kernel.org>,
        Dmitry Vyukov <dvyukov@...gle.com>, kasan-dev@...glegroups.com,
        Alexander Potapenko <glider@...gle.com>,
        Kees Cook <keescook@...omium.org>
Subject: Re: [PATCH] x86/entry/64: wipe KASAN stack shadow in
 rewind_stack_do_exit()

On 08/28/2018 01:38 PM, Jann Horn wrote:

>>
>>
>> Why this has to be done in the rewind_stack_do_exit()?
>> Are there any problems with calling the kasan_unpoison_task_stack(current) from oops_end(), before the rewind_stack_do_exit()?
> 
> Ooh, good point! I didn't see that KASAN instrumentation is disabled
> for dumpstack.c. 

It doesn't really matter. This would work with instrumented oops_end() as well.
kasan_unpoison_task_stack() will unpoison everything including oops_end's stack.
It would be also ok if kasan_unpoison_task_stack() instrumented, or calling any number of instrumented functions
in between kasan_unpoison_task_stack() and rewind_stack_do_exit(). As long as we return from these functions before
the rewind_stack_do_exit(), the stack will be unpoisoned on return.