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SubjectRe: [PATCH v4] kasan/quarantine: fix bugs on qlist_move_cache()
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On 07/04/2016 07:31 AM, 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.
>
> v4: fix cache size bug s/cache->size/obj_cache->size/
> 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..b2e1827 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;
> struct kmem_cache *obj_cache = qlink_to_cache(qlink);
>
> - if (obj_cache == cache) {
> - if (unlikely(from->head == qlink)) {
> - from->head = curr->next;
> - prev = curr;
> - } else
> - prev->next = curr->next;
> - if (unlikely(from->tail == qlink))
> - from->tail = curr->next;
> - from->bytes -= cache->size;
> - qlist_put(to, qlink, cache->size);
> - } else {
> - prev = curr;
> - }
> curr = curr->next;

Nit: Wouldn't be more appropriate to swap 'curr' and 'qlink' variable names?
Because now qlink is acts as a "current" pointer.

> +
> + if (obj_cache == cache)
> + qlist_put(to, qlink, obj_cache->size);
> + else
> + qlist_put(from, qlink, obj_cache->size);
> }
> }
>
>

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