From 49d9991a18f9aae7b14abbd9c1cc87555330a769 Mon Sep 17 00:00:00 2001 From: David Vrabel Date: Wed, 4 Mar 2015 11:14:47 +0000 Subject: [PATCH] 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 Signed-off-by: David S. Miller --- drivers/net/xen-netback/netback.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c index c4d68d768408..f1d84fb1eba8 100644 --- a/drivers/net/xen-netback/netback.c +++ b/drivers/net/xen-netback/netback.c @@ -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, -- 2.20.1