lkml.org 
[lkml]   [2013]   [Nov]   [7]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v2 01/11] rbtree: Fix rbtree_postorder_for_each_entry_safe() iterator
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.



\
 
 \ /
  Last update: 2013-11-07 23:21    [W:0.053 / U:0.144 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site