linux-kernel - Re: [PATCH V2] x86/numa: kernel stack corruption fix

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Date:	Wed, 8 Apr 2015 11:09:16 +0800
From:	Dave Young <dyoung@...hat.com>
To:	Xishi Qiu <qiuxishi@...wei.com>
Cc:	Baoquan He <bhe@...hat.com>, x86@...nel.org,
	linux-kernel@...r.kernel.org, tglx@...utronix.de,
	akpm@...ux-foundation.org, isimatu.yasuaki@...fujitsu.com,
	mingo@...hat.com, hpa@...or.com
Subject: Re: [PATCH V2] x86/numa: kernel stack corruption fix

On 04/08/15 at 10:41am, Xishi Qiu wrote:
> On 2015/4/8 10:18, Baoquan He wrote:
> 
> > On 04/08/15 at 09:59am, Xishi Qiu wrote:
> >> On 2015/4/8 9:46, Dave Young wrote:
> >>
> >>>>>  
> >>>>> -	/* Mark all kernel nodes. */
> >>>>> +	/*
> >>>>> +	 * Mark all kernel nodes.
> >>>>> +	 *
> >>>>> +	 * In case booting with mem=nn[kMG] or in kdump kernel, numa_meminfo
> >>>>
> >>>> Hi Dave,
> >>>>
> >>>> It should both set mem=xx and numa=off, then numa_meminfo may not include all
> >>>> the memblock.reserved memory, right?
> >>>
> >>> Yasuaki Ishimatsu suggests to remove numa=off in comment because in theory there's such
> >>> possiblity that it may happen even without numa=off. Just consider the non-snb board..
> >>>
> >>> Thanks
> >>> Dave
> >>>
> >>
> >> Hi Dave,
> >>
> >> I made a mistake, when numa is on, numa_meminfo is from SRAT, but it will be cut
> >> in numa_cleanup_meminfo(), so the bug is not related to numa on/off. Your comment
> >> is right.
> > 
> > Hi Xishi,
> > 
> >>From code flow it's exact as you said. And if remove numa=off bug should
> > be reproduced alwasy. I talked to Dave, he said error didn't occur when
> > he remove numa=off. That is too weird.
> > 
> 
> Hi Baoquan,
> 
> May be it wrote over end of numa mask bitmap, but the stack can still run,
> so there is no Call Trace. 
> How about add some printk to see if it has written over? 

Oops, Redhat kdump always add numa=off in 2nd kernel commandline, but I did
not notice I removed it during test.

So yes, the issue does not depend on numa=off.

Thanks
Dave
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