Messages in this thread | | | Date | Thu, 07 Nov 2013 13:58:15 -0800 | From | Cody P Schafer <> | Subject | Re: [PATCH v2 01/11] rbtree: Fix rbtree_postorder_for_each_entry_safe() iterator |
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On 11/07/2013 01:38 PM, Andrew Morton wrote: > On Wed, 6 Nov 2013 17:42:30 -0800 Cody P Schafer <cody@linux.vnet.ibm.com> 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?
I can't reproduce the oopses (at all) with my build/gcc version, but Jan has reported seeing them (not in zswap, however).
> > IOW, is there any need to fix this in 3.12 or earlier? >
The zswap usage change showed up in 3.12. In my opinion, it is probably a good idea to apply the fix to 3.12.
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