linux-kernel - Re: [PATCH] vmcore: prevent PT_NOTE p_memsz overflow during header update

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Date:	Sun, 02 Feb 2014 14:25:25 -0800
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	"Pearson\, Greg" <greg.pearson@...com>,
	"vgoyal\@redhat.com" <vgoyal@...hat.com>,
	"d.hatayama\@jp.fujitsu.com" <d.hatayama@...fujitsu.com>,
	"holzheu\@linux.vnet.ibm.com" <holzheu@...ux.vnet.ibm.com>,
	"dhowells\@redhat.com" <dhowells@...hat.com>,
	"paul.gortmaker\@windriver.com" <paul.gortmaker@...driver.com>,
	"linux-kernel\@vger.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] vmcore: prevent PT_NOTE p_memsz overflow during header update

Andrew Morton <akpm@...ux-foundation.org> writes:

> On Sat, 1 Feb 2014 01:07:29 +0000 "Pearson, Greg" <greg.pearson@...com> wrote:
>
>> As far as I know the only consequence of dropping a PT_NOTE entry is 
>> that it would not be available in the crash dump for use in debugging. 
>> I'm not sure how important this data might be for triage. I'm guessing 
>> that in cases where one of these strange PT_NOTE entries shows up with a 
>> size that causes an overflow it probably isn't even a real PT_NOTE entry 
>> so dropping it won't matter, but that's a guess at this point since I'm 
>> still trying to figure out how the bogus entries were created.
>
> Can we detect the crazy-huge notes, skip them and then proceed with
> the following sanely-sized ones?

The only way we can have following sanely-sized notes is if they are in
a separate note segment (one of our extensions for kdump and
/proc/vmcore merges them together).

Eric
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