linux-kernel - Re: Question regarding RT patches for ARM

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] [day] [month] [year] [list]

Date:   Thu, 18 May 2017 22:10:33 +0200
From:   Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:     Fawad Lateef <fawadlateef@...il.com>
Cc:     Eric Nelson <eric@...int.com>, GuJiangfei <qiledexin@....com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        kernelnewbies <kernelnewbies@...nelnewbies.org>,
        linux-rt-users@...r.kernel.org
Subject: Re: Question regarding RT patches for ARM

On 2017-05-18 13:08:32 [+0200], Fawad Lateef wrote:
> Hi Sebastian,
Hi Fawad,

> > Of this "page fault" happens on boot, it has to do something without
> > your .config + hw combination. If it happens at rune-time it is probably
> > triggered by a driver or an application is triggering this.
> >
> 
> Yes, this happens at run-time and not always. Sometimes hardware just
> hangs/stalls.

So this sounds like a race condition.

> As now RT is widely used on ARM so to me seems like it something
> related to hardware design/setting OR application.
> 
> Another question: Is RT user-space application can make kernel/system
> crash? As to me kernel should kill the app but let itself running
> _but_ not sure in the case of RT patched kernel.

This is correct. With RT or without it: a use space should not be able
to crash the kernel.
It is possible that a race within a driver triggers more reliably on RT.
I would recommend to strip down the system to the minimum where the
issue should not trigger. And then slowly increase the "enabled"
hardware components so you might get an idea when or what could cause
it.

> Thanks,
> 
> Fawad Lateef

Sebastian