Re: [RFC] [PATCH 2.6.37-rc5-tip 5/20] 5: Uprobes:register/unregister probes.
From: Peter Zijlstra
Date: Wed Jan 26 2011 - 05:11:29 EST
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
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