Re: [RFC] [PATCH 2.6.37-rc5-tip 5/20] 5: Uprobes:register/unregister probes.

[Peter Zijlstra]

On Wed, 2011-01-26 at 13:25 +0530, Srikar Dronamraju wrote:
> 
> > > +
> > > +               list_add(&mm->uprobes_list, &tmp_list);
> > > +               mm->uprobes_vaddr = vma->vm_start + offset;
> > > +       }
> > > +       spin_unlock(&mapping->i_mmap_lock);
> > 
> > Both this and unregister are racy, what is to say:
> >  - the vma didn't get removed from the mm
> >  - no new matching vma got added
> > 
> 
> register_uprobe, unregister_uprobe, uprobe_mmap are all synchronized by
> uprobes_mutex. So I dont see one unregister_uprobe getting thro when
> another register_uprobe is working with a vma.
> 
> If I am missing something elementary, please explain a bit more.

afaict you're not holding the mmap_sem, so userspace can simply unmap
the vma.
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