linux-kernel - Re: [BUGFIX] NULL pointer dereference in __vm_enough

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Date:	Sun, 12 Aug 2007 22:09:17 +0800
From:	WU Fengguang <wfg@...l.ustc.edu.cn>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
Cc:	Balbir Singh <balbir@...ux.vnet.ibm.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Paul Moore <paul.moore@...com>,
	Stephen Smalley <sds@...ch.ncsc.mil>,
	Chris Vance <cvance@....com>, Wayne Salamon <wsalamon@....com>,
	James Morris <jmorris@...hat.com>, dgoeddel@...stedcs.com
Subject: Re: [BUGFIX] NULL pointer dereference in __vm_enough_memory()

On Sun, Aug 12, 2007 at 02:19:05PM +0100, Alan Cox wrote:
> > > Great! So the problem might have existed for some time, but we never
> > > saw it due to default over commit values? Were you using these values
> > > for over commit even before?
> > 
> > No I changed it several weeks ago to stop my desktop from freezing.
> > So yes, the bug may have been there for a while.
> 
> The bug is the new exec with lots of arguments code. It tries to insert a
> vm struct without having a valid current->mm. That isn't permitted and
> never had been (which is also why it broke the sparc mmu code etc).
> 
> You'll need to change the kernel security interface a little to make this
> fly - I think the following should do it.
> 
> 	- make __vm_enough_memory take a struct mm pointer and use it
> 	- make security_ops pass the extra current->mm
> 	- add a vm_enough_memory_mm security op
> 	- use security_vm_enough_memory_mm(mm, ...) in __insert_vm_struct
> 
> I'll knock up a quick patch and see what is needed (someone else can do
> the selinux changes)

Thank you!

Count me for one - but CC SELinux maintainers first :)

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