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SubjectRe: [PATCH net-next v2 6/9] xen-netback: Handle guests with too many frags
On 16/12/13 18:09, Wei Liu wrote:
>>>> diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c
>>>> index e26cdda..f6ed1c8 100644
>>>> --- a/drivers/net/xen-netback/netback.c
>>>> +++ b/drivers/net/xen-netback/netback.c
>>>> @@ -906,11 +906,15 @@ static struct gnttab_map_grant_ref *xenvif_get_requests(struct xenvif *vif,
>>>> u16 pending_idx = *((u16 *)skb->data);
>>>> int start;
>>>> pending_ring_idx_t index;
>>>> - unsigned int nr_slots;
>>>> + unsigned int nr_slots, frag_overflow = 0;
>>>>
>>>> /* At this point shinfo->nr_frags is in fact the number of
>>>> * slots, which can be as large as XEN_NETBK_LEGACY_SLOTS_MAX.
>>>> */
>>>> + if (shinfo->nr_frags > MAX_SKB_FRAGS) {
>>>> + frag_overflow = shinfo->nr_frags - MAX_SKB_FRAGS;
>>>> + shinfo->nr_frags = MAX_SKB_FRAGS;
>>>> + }
>>>> nr_slots = shinfo->nr_frags;
>>>>
>>>
>>> It is also probably better to check whether shinfo->nr_frags is too
>>> large which makes frag_overflow > MAX_SKB_FRAGS. I know skb should be
>>> already be valid at this point but it wouldn't hurt to be more careful.
>> Ok, I've added this:
>> /* At this point shinfo->nr_frags is in fact the number of
>> * slots, which can be as large as XEN_NETBK_LEGACY_SLOTS_MAX.
>> */
>> + if (shinfo->nr_frags > MAX_SKB_FRAGS) {
>> + if (shinfo->nr_frags > XEN_NETBK_LEGACY_SLOTS_MAX) return NULL;
>> + frag_overflow = shinfo->nr_frags - MAX_SKB_FRAGS;
>>
>
> What I suggested is
>
> BUG_ON(frag_overflow > MAX_SKB_FRAGS)

Ok, I've changed it.

Zoli



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