linux-kernel - Re: [kernel-hardening] Re: Add overflow protection to kref

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Date:	Sat, 25 Feb 2012 00:14:43 +0200
From:	"PaX Team" <pageexec@...email.hu>
To:	Greg KH <gregkh@...uxfoundation.org>,
	David Windsor <dwindsor@...il.com>
CC:	Roland Dreier <roland@...estorage.com>,
	Djalal Harouni <tixxdz@...ndz.org>,
	Vasiliy Kulikov <segoon@...nwall.com>,
	kernel-hardening@...ts.openwall.com,
	Kees Cook <keescook@...omium.org>,
	Ubuntu security discussion <ubuntu-hardened@...ts.ubuntu.com>,
	linux-kernel@...r.kernel.org, spender@...ecurity.net
Subject: Re: [kernel-hardening] Re: Add overflow protection to kref

On 24 Feb 2012 at 14:04, David Windsor wrote:

> Suggestions on recovering from an overflow here?

do what PaX does? :)

1. saturate the refcount
2. report the event (pax_report_refcount_overflow)
3. kill the triggering userland process (this may be optional but it's a good measure
   if you have stuff like grsecurity's lockout feature)

> 2. Detect the overflow before it happens, don't increment the counter,
> issue a warning but no BUG.
> This could also lead to some "undefined" behavior in subsystems.

it's called a memory leak :).

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