From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from noname.neutralserver.com ([70.84.186.210]:45555 "EHLO noname.neutralserver.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1764593AbXHVJRO (ORCPT ); Wed, 22 Aug 2007 05:17:14 -0400 Date: Wed, 22 Aug 2007 11:48:52 +0300 From: Dan Aloni Subject: Re: [patch 3/3] mm: variable length argument support Message-ID: <20070822084852.GA12314@localdomain> References: <20070613100334.635756997@chello.nl> <20070613100835.014096712@chello.nl> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20070613100835.014096712@chello.nl> Sender: linux-arch-owner@vger.kernel.org To: Peter Zijlstra Cc: linux-kernel@vger.kernel.org, parisc-linux@lists.parisc-linux.org, linux-mm@kvack.org, linux-arch@vger.kernel.org, Ollie Wild , Andrew Morton , Ingo Molnar , Andi Kleen List-ID: On Wed, Jun 13, 2007 at 12:03:37PM +0200, Peter Zijlstra wrote: > From: Ollie Wild > > 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. Signed-off-by: Dan Aloni diff --git a/mm/mmap.c b/mm/mmap.c index 906ed40..6e021df 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -163,10 +163,12 @@ int __vm_enough_memory(long pages, int cap_sys_admin) if (!cap_sys_admin) allowed -= allowed / 32; allowed += total_swap_pages; - - /* Don't let a single process grow too big: - leave 3% of the size of this process for other processes */ - allowed -= current->mm->total_vm / 32; + + if (current->mm) { + /* Don't let a single process grow too big: + leave 3% of the size of this process for other processes */ + allowed -= current->mm->total_vm / 32; + } /* * cast `allowed' as a signed long because vm_committed_space -- Dan Aloni XIV LTD, http://www.xivstorage.com da-x (at) monatomic.org, dan (at) xiv.co.il