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Commit 49d9991a authored by David Vrabel's avatar David Vrabel Committed by David S. Miller
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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: default avatarDavid Vrabel <david.vrabel@citrix.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent d63951d7

drivers/net/xen-netback/netback.c

+6 −1
Original line number Diff line number Diff line
@@ -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,