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xen-netback: unref frags when handling a from-guest skb with a frag list 

Every time a VIF is destroyed up to 256 pages may be leaked if packets
with more than MAX_SKB_FRAGS frags were transmitted from the guest.
Even worse, if another user of ballooned pages allocated one of these
ballooned pages it would not handle the unexpectedly >1 page count
(e.g., gntdev would deadlock when unmapping a grant because the page
count would never reach 1).

When handling a from-guest skb with a frag list, unref the frags
before releasing them so they are freed correctly when the VIF is
destroyed.

Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
David Vrabel 2015-03-04 11:14:47 +00:00 committed by David S. Miller
parent d63951d744
commit 49d9991a18
1 changed files with 6 additions and 1 deletions
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7
drivers/net/xen-netback/netback.c
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@ -1349,7 +1349,7 @@ static int xenvif_handle_frag_list(struct xenvif_queue *queue, struct sk_buff *s
{
unsigned int offset = skb_headlen(skb);
skb_frag_t frags[MAX_SKB_FRAGS];
int i;
int i, f;
struct ubuf_info *uarg;
struct sk_buff *nskb = skb_shinfo(skb)->frag_list;
@ -1389,6 +1389,11 @@ static int xenvif_handle_frag_list(struct xenvif_queue *queue, struct sk_buff *s
frags[i].page_offset = 0;
skb_frag_size_set(&frags[i], len);
}
/* Release all the original (foreign) frags. */
for (f = 0; f < skb_shinfo(skb)->nr_frags; f++)
skb_frag_unref(skb, f);
/* swap out with old one */
memcpy(skb_shinfo(skb)->frags,
frags,