linux-kernel - Re: [GIT PULL] Fix for Integrity subsystem null pointer deref

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Date:	Wed, 29 Oct 2014 11:51:40 -0700
From:	Andy Lutomirski <luto@...capital.net>
To:	Dan Carpenter <dan.carpenter@...cle.com>
Cc:	Mimi Zohar <zohar@...ux.vnet.ibm.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	LSM List <linux-security-module@...r.kernel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	"security@...nel.org" <security@...nel.org>,
	James Morris <jmorris@...ei.org>
Subject: Re: [GIT PULL] Fix for Integrity subsystem null pointer deref

On Wed, Oct 29, 2014 at 11:36 AM, Dan Carpenter
<dan.carpenter@...cle.com> wrote:
> On Wed, Oct 29, 2014 at 09:23:45AM -0700, Andy Lutomirski wrote:
>> I have no idea what the semantics are.  All I'm saying is that it
>> looks like the code still accesses memory past the end of the buffer.
>> The buffer isn't a null pointer, so the symptom is different, but it
>> may still be a security bug.
>>
>> --Andy
>
> It only reads one byte into the struct "xattr_data->type" so checking
> for non-zero is sufficient and the patch is fine.

Indeed.  Still... eww.  I don't like code that, upon local inspection,
is apparently wrong, even though it's coincidentally correct due to
some other far away condition.

--Andy

>
> I fixed that exact same bug in lustre last week where the xattr size is
> not zero but it's less than the size of the struct.  So this seems like
> maybe it could be a common anti-pattern though.
>
> regards,
> dan carpenter
>



-- 
Andy Lutomirski
AMA Capital Management, LLC
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