From: Cody P Schafer <cody@linux.vnet.ibm.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: EXT4 <linux-ext4@vger.kernel.org>, Jan Kara <jack@suse.cz>,
rostedt@goodmis.org, Seth Jennings <sjennings@variantweb.net>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v2 01/11] rbtree: Fix rbtree_postorder_for_each_entry_safe() iterator
Date: Thu, 07 Nov 2013 13:58:15 -0800 [thread overview]
Message-ID: <527C0CF7.705@linux.vnet.ibm.com> (raw)
In-Reply-To: <20131107133800.c779b2f2b2ec73c91cd25f47@linux-foundation.org>
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.
next prev parent reply other threads:[~2013-11-07 21:58 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-11-07 1:42 [PATCH v2 00/11] rbtree: postorder iteration: fix, add tests, and use in various places Cody P Schafer
2013-11-07 1:42 ` [PATCH v2 01/11] rbtree: Fix rbtree_postorder_for_each_entry_safe() iterator Cody P Schafer
2013-11-07 11:51 ` Michel Lespinasse
2013-11-07 18:59 ` Cody P Schafer
2013-11-07 21:38 ` Andrew Morton
2013-11-07 21:58 ` Cody P Schafer [this message]
2013-11-07 22:14 ` Jan Kara
2013-11-07 1:42 ` [PATCH v2 02/11] rbtree/test: move rb_node to the middle of the test struct Cody P Schafer
2013-11-07 11:52 ` Michel Lespinasse
2013-11-07 1:42 ` [PATCH v2 03/11] rbtree/test: test rbtree_postorder_for_each_entry_safe() Cody P Schafer
2013-11-07 11:54 ` Michel Lespinasse
2013-11-07 1:42 ` [PATCH v2 04/11] net ipset: use rbtree postorder iteration instead of opencoding Cody P Schafer
2013-11-07 1:42 ` [PATCH v2 05/11] trace/trace_stat: use rbtree postorder iteration helper " Cody P Schafer
2013-11-07 1:42 ` [PATCH v2 06/11] fs/ubifs: " Cody P Schafer
2013-11-07 1:42 ` Cody P Schafer
2013-11-07 1:42 ` Cody P Schafer
2013-11-07 1:42 ` [PATCH v2 07/11] fs/ext4: " Cody P Schafer
2013-11-07 9:28 ` Jan Kara
2013-11-07 1:42 ` [PATCH v2 08/11] fs/jffs2: " Cody P Schafer
2013-11-07 1:42 ` Cody P Schafer
2013-11-07 1:42 ` Cody P Schafer
2013-11-07 1:42 ` [PATCH v2 09/11] fs/ext3: " Cody P Schafer
2013-11-07 8:17 ` Jan Kara
2013-11-07 1:42 ` [PATCH v2 10/11] mtd/ubi: " Cody P Schafer
2013-11-07 1:42 ` Cody P Schafer
2013-11-07 1:42 ` Cody P Schafer
2013-11-07 1:42 ` [PATCH v2 11/11] sh/dwarf: use rbtree postorder iteration helper instead of solution using repeated Cody P Schafer
2013-11-07 1:42 ` [PATCH v2 11/11] sh/dwarf: use rbtree postorder iteration helper instead of solution using repeated rb_erase() Cody P Schafer
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