linux-kernel - Re: perf: fuzzer KASAN unwind_get_return

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: <alpine.DEB.2.20.1611170924260.10901@macbook-air>
Date:   Thu, 17 Nov 2016 09:25:58 -0500 (EST)
From:   Vince Weaver <vincent.weaver@...ne.edu>
To:     Josh Poimboeuf <jpoimboe@...hat.com>
cc:     Dmitry Vyukov <dvyukov@...gle.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Vince Weaver <vincent.weaver@...ne.edu>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        "davej@...emonkey.org.uk" <davej@...emonkey.org.uk>,
        Stephane Eranian <eranian@...il.com>
Subject: Re: perf: fuzzer KASAN unwind_get_return_address

On Thu, 17 Nov 2016, Josh Poimboeuf wrote:

> On Thu, Nov 17, 2016 at 10:48:27AM +0100, Dmitry Vyukov wrote:
> > Just in case, there is currently a known KASAN false positive related
> > to longjmp's on GPFs. When a syscall hits GPF stack is unwound to
> > kernel entry point, this leaves a bunch of stray poisoned redzones on
> > the thread stack. They later cause false stack-out-of-bounds reports.
> > 
> > But this does not seem to be the case here. Kernel is not tainted. And
> > shadow at the bottom of the reports looks sane.
> > 
> > But if that's the case somehow, we will need to add
> > kasan_unpoison_remaining_stack() call before a longjmp like we did for
> > jprobe_return():
> > https://groups.google.com/d/msg/kasan-dev/Hzox58yZ4MU/TOdFoWMuBQAJ
> 
> I'm pretty sure this isn't a KASAN false positive.  The unwinder does
> actually seem to be accessing a bad area of the stack, in the middle of
> a function's stack frame.

I'm having trouble reproducing it on a few other machines I have fuzzing.
So there might be some kernel option contributing, I need to compare 
.configs.

Also the machine that easily triggers the problem I'm compiling with 
gcc-5.4 where the machines I can't are using gcc-4.9.

Vince