Re: [PATCH v2 01/11] rbtree: Fixrbtree_postorder_for_each_entry_safe() iterator

From: Andrew Morton
Date: Thu Nov 07 2013 - 16:38:17 EST

On Wed, 6 Nov 2013 17:42:30 -0800 Cody P Schafer <cody@xxxxxxxxxxxxxxxxxx> wrote:

> The iterator rbtree_postorder_for_each_entry_safe() relies on pointer
> underflow behavior when testing for loop termination. In particular
> it expects that
> &rb_entry(NULL, type, field)->field
> is NULL. But the result of this expression is not defined by a C standard
> and some gcc versions (e.g. 4.3.4) assume the above expression can never
> be equal to NULL. The net result is an oops because the iteration is not
> properly terminated.
> Fix the problem by modifying the iterator to avoid pointer underflows.

So the sole caller is in zswap.c. Is that code actually generating oopses?

IOW, is there any need to fix this in 3.12 or earlier?
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