linux-kernel - Re: [PATCH] bootmem: avoid freeing to bootmem after bootmem is done

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Date:	Mon, 27 Jul 2015 11:59:51 +0100
From:	Mel Gorman <mgorman@...e.de>
To:	Chris Metcalf <cmetcalf@...hip.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>,
	Pekka Enberg <penberg@...nel.org>,
	Paul McQuade <paulmcquad@...il.com>,
	Tang Chen <tangchen@...fujitsu.com>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] bootmem: avoid freeing to bootmem after bootmem is done

On Fri, Jul 24, 2015 at 04:53:46PM -0400, Chris Metcalf wrote:
> Bootmem isn't popular any more, but some architectures still use
> it, and freeing to bootmem after calling free_all_bootmem_core()
> can end up scribbling over random memory.  Instead, make sure the
> kernel panics by ensuring the node_bootmem_map field is non-NULL
> when are freeing or marking bootmem.
> 
> An instance of this bug was just fixed in the tile architecture
> ("tile: use free_bootmem_late() for initrd") and catching this case
> more widely seems like a good thing.
> 
> Signed-off-by: Chris Metcalf <cmetcalf@...hip.com>

In general it looks fine  but you could just WARN_ON, return and still
boot the kernel too. Obviously it would need to be fixed but Linus will
push back if he spots a BUG_ON when there was a recovery option.

-- 
Mel Gorman
SUSE Labs
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