Re: Linux kernel: powerpc: KVM guest can trigger host crash on Power8

From: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>
To: Michael Ellerman <mpe@ellerman.id.au>
Cc: oss-security@lists.openwall.com,
	"debian-powerpc@lists.debian.org"
	<debian-powerpc@lists.debian.org>,
	linuxppc-dev@lists.ozlabs.org
Subject: Re: Linux kernel: powerpc: KVM guest can trigger host crash on Power8
Date: Wed, 27 Oct 2021 13:09:47 +0200	[thread overview]
Message-ID: <c21c7a0e-95f1-e6d2-a04c-fb99d801e8da@physik.fu-berlin.de> (raw)
In-Reply-To: <874k92bubv.fsf@mpe.ellerman.id.au>

Hi Michael!

On 10/27/21 13:06, Michael Ellerman wrote:
> John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de> writes:
>> Hi Michael!
>>
>> On 10/27/21 07:30, Michael Ellerman wrote:
>>> I did test the repro case you gave me before (in the bugzilla), which
>>> was building glibc, that passes for me with a patched host.
>>
>> Did you manage to crash the unpatched host?
> 
> Yes, the parallel builds of glibc you described crashed the unpatched
> host 100% reliably for me.

OK, that is very good news!

> I also have a standalone reproducer I'll send you.

Thanks, that would be helpful!

>> Also, I'll try a kernel from git with Debian's config.
>>
>>> I guess we have yet another bug.
>>>
>>> I tried the following in a debian BE VM and it completed fine:
>>>
>>>  $ dget -u http://ftp.debian.org/debian/pool/main/g/git/git_2.33.1-1.dsc
>>>  $ sbuild -d sid --arch=powerpc --no-arch-all git_2.33.1-1.dsc
>>>
>>> Same for ppc64.
>>>
>>> And I also tried both at once, repeatedly in a loop.
>>
>> Did you try building gcc-11 for powerpc and ppc64 both at once?
> 
> No, I will try that now.

OK, great!

Adrian

-- 
 .''`.  John Paul Adrian Glaubitz
: :' :  Debian Developer - glaubitz@debian.org
`. `'   Freie Universitaet Berlin - glaubitz@physik.fu-berlin.de
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