Messages in this thread | | | Date | Wed, 22 Aug 2007 17:02:51 +0800 | From | Fengguang Wu <> | Subject | Re: [patch 3/3] mm: variable length argument support |
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On Wed, Aug 22, 2007 at 11:48:52AM +0300, Dan Aloni wrote: > On Wed, Jun 13, 2007 at 12:03:37PM +0200, Peter Zijlstra wrote: > > From: Ollie Wild <aaw@google.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. > > > Signed-off-by: Dan Aloni <da-x@monatomic.org> > > 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 >
FYI: This bug has been fixed by Alan Cox: http://lkml.org/lkml/2007/8/13/782.
But thanks anyway~
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