cryptoapi incorrect struct page usage

It seems that cryptoapi usage wrt mm is not safe. At least both ipsec and cryptoloop practise these kinds of things :

example from net/xfrm/xfrm_algo.c

int
skb_to_sgvec(struct sk_buff *skb, struct scatterlist *sg, int offset, int len) {
int start = skb_headlen(skb);
int i, copy = start - offset;
int elt = 0;

   if (copy > 0) {
       if (copy > len)
           copy = len;
       sg[elt].page = virt_to_page(skb->data + offset);
       sg[elt].offset = (unsigned long)(skb->data + offset) % PAGE_SIZE;
       sg[elt].length = copy;

so unpinned pages are passed to cryptoapi. Nothing prevents these pages from being swapped out. Something like get_user_pages() is needed to pin these pages for the duration of crypto operations. Comments?

--Mika

The page at skb->data was allocated by the skbuff allocation layer, it has therefore a lifetime the size of the SKB itself.

The crypto API call is finished before we can possibly free up the SKB, so nothing bad can happen.