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SubjectRe: [PATCH v3] kasan/quarantine: fix bugs on qlist_move_cache()
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On 07/04/2016 07:36 AM, Joonsoo Kim wrote:
> On Fri, Jul 01, 2016 at 05:17:10PM +0300, Andrey Ryabinin wrote:
>>
>>
>> On 07/01/2016 05:02 PM, js1304@gmail.com wrote:
>>> From: Joonsoo Kim <iamjoonsoo.kim@lge.com>
>>>
>>> There are two bugs on qlist_move_cache(). One is that qlist's tail
>>> isn't set properly. curr->next can be NULL since it is singly linked
>>> list and NULL value on tail is invalid if there is one item on qlist.
>>> Another one is that if cache is matched, qlist_put() is called and
>>> it will set curr->next to NULL. It would cause to stop the loop
>>> prematurely.
>>>
>>> These problems come from complicated implementation so I'd like to
>>> re-implement it completely. Implementation in this patch is really
>>> simple. Iterate all qlist_nodes and put them to appropriate list.
>>>
>>> Unfortunately, I got this bug sometime ago and lose oops message.
>>> But, the bug looks trivial and no need to attach oops.
>>>
>>> v3: fix build warning
>>>
>>> Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
>>> ---
>>> mm/kasan/quarantine.c | 21 +++++++--------------
>>> 1 file changed, 7 insertions(+), 14 deletions(-)
>>>
>>> diff --git a/mm/kasan/quarantine.c b/mm/kasan/quarantine.c
>>> index 4973505..cf92494 100644
>>> --- a/mm/kasan/quarantine.c
>>> +++ b/mm/kasan/quarantine.c
>>> @@ -238,30 +238,23 @@ static void qlist_move_cache(struct qlist_head *from,
>>> struct qlist_head *to,
>>> struct kmem_cache *cache)
>>> {
>>> - struct qlist_node *prev = NULL, *curr;
>>> + struct qlist_node *curr;
>>>
>>> if (unlikely(qlist_empty(from)))
>>> return;
>>>
>>> curr = from->head;
>>> + qlist_init(from);
>>> while (curr) {
>>> struct qlist_node *qlink = curr;
>>
>> Can you please also get rid of either qlink or curr.
>> Those are essentially the same pointers.
>
> Hello,
>
> Before putting the qlist_node to the list, we need to calculate
> curr->next and remember it to iterate the list. I use curr
> for this purpose so qlink and curr are not the same pointer.
>

Right, I missed the fact that qlist_put() changes ->next pointer, thus we can't fetch ->next after qlist_put().

> Thanks.
>

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