linux-kernel - Re: [patch 3/3] mm: variable length argument support

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Message-Id: <1187772842.6114.282.camel@twins>
Date:	Wed, 22 Aug 2007 10:54:02 +0200
From:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
To:	Dan Aloni <da-x@...atomic.org>
Cc:	linux-kernel@...r.kernel.org, parisc-linux@...ts.parisc-linux.org,
	linux-mm@...ck.org, linux-arch@...r.kernel.org,
	Ollie Wild <aaw@...gle.com>, Andrew Morton <akpm@...l.org>,
	Ingo Molnar <mingo@...e.hu>, Andi Kleen <ak@...e.de>,
	Alan Cox <alan@...rguk.ukuu.org.uk>
Subject: Re: [patch 3/3] mm: variable length argument support

On Wed, 2007-08-22 at 11:48 +0300, Dan Aloni wrote:
> On Wed, Jun 13, 2007 at 12:03:37PM +0200, Peter Zijlstra wrote:
> > From: Ollie Wild <aaw@...gle.com>
> > 
> > Remove the arg+env limit of MAX_ARG_PAGES by copying the strings directly
> > from the old mm into the new mm.
> > 
> [...]
> > +static int __bprm_mm_init(struct linux_binprm *bprm)
> > +{
> [...]
> > +	vma->vm_flags = VM_STACK_FLAGS;
> > +	vma->vm_page_prot = protection_map[vma->vm_flags & 0x7];
> > +	err = insert_vm_struct(mm, vma);
> > +	if (err) {
> > +		up_write(&mm->mmap_sem);
> > +		goto err;
> > +	}
> > +
> 
> That change causes a crash in khelper when overcommit_memory = 2 
> under 2.6.23-rc3.
> 
> When a khelper execs, at __bprm_mm_init() current->mm is still NULL.
> insert_vm_struct() calls security_vm_enough_memory(), which calls 
> __vm_enough_memory(), and that's where current->mm->total_vm gets 
> dereferenced.

Alan proposed this patch:

http://lkml.org/lkml/2007/8/13/782


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