On Wed, 24 Mar 2010 22:47:42 +0100
Andrea Arcangeli <aarcange@redhat.com> wrote:

quoted text
> I think you mistaken a VM_BUG_ON for a:
> 
>   if (could_be_null->something) {
>      WARN_ON(1);
>      return -ESOMETHING;
>   }
> 
> adding a VM_BUG_ON(inode->something) would _still_ be as exploitable
> as the null pointer deference, because it's a DoS. It's not really a
> big deal of an exploit but it _sure_ need fixing.

Ah, but that's the point: these NULL pointer dereferences were not DoS
vulnerabilities - they were full privilege-escalation affairs.  Since
then, some problems have been fixed and some distributors have started
shipping smarter configurations.  But, on quite a few systems a NULL
dereference still has the potential to be fully exploitable; if there's
a possibility of it happening I think we should test for it.  A DoS is
a much better outcome...

jon
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