linux-kernel - Re: [BUG 3.12.rc4] Oops: unable to handle kernel paging request during shutdown

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Message-ID: <20131018063017.GE14264@gmail.com>
Date:	Fri, 18 Oct 2013 08:30:17 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	Frederic Weisbecker <fweisbec@...il.com>
Cc:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Knut Petersen <Knut_Petersen@...nline.de>,
	Thomas Gleixner <tglx@...utronix.de>, Greg KH <greg@...ah.com>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [BUG 3.12.rc4] Oops: unable to handle kernel paging request
 during shutdown


* Frederic Weisbecker <fweisbec@...il.com> wrote:

> On Tue, Oct 15, 2013 at 08:40:25AM +0200, Ingo Molnar wrote:
> > 
> > * Frederic Weisbecker <fweisbec@...il.com> wrote:
> > 
> > > I've been thinking that CONFIG_DEBUG_LIST could help. Unfortunately it's 
> > > good to spot list APIs misuse but, if Linus is right, the problem may be 
> > > that the list belongs to an object that has been freed, and I believe 
> > > that won't detect such a thing.
> > 
> > Use-after free should be reliably detectable via CONFIG_DEBUG_PAGEALLOC=y.
> > 
> > A couple of years ago I wrote a list debugging beast that would catch 
> > use-after-free mishaps (sent it to lkml too IIRC), but it was a bit 
> > complex and I never found the time to nurse it upstream.
> 
> Ok, well CONFIG_DEBUG_PAGEALLOC=y should work for list as for anything, 
> right?

Correct - but it adds non-trivial overhead so in some cases it hides 
races.

Thanks,

	Ingo
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