| From 869831b11cf4bb5ec2d80294d68367bb152d9fe1 Mon Sep 17 00:00:00 2001 |
| From: Jason Wang <jasowang@redhat.com> |
| Date: Wed, 13 Nov 2013 14:00:40 +0800 |
| Subject: macvtap: limit head length of skb allocated |
| |
| From: Jason Wang <jasowang@redhat.com> |
| |
| [ Upstream commit 16a3fa28630331e28208872fa5341ce210b901c7 ] |
| |
| We currently use hdr_len as a hint of head length which is advertised by |
| guest. But when guest advertise a very big value, it can lead to an 64K+ |
| allocating of kmalloc() which has a very high possibility of failure when host |
| memory is fragmented or under heavy stress. The huge hdr_len also reduce the |
| effect of zerocopy or even disable if a gso skb is linearized in guest. |
| |
| To solves those issues, this patch introduces an upper limit (PAGE_SIZE) of the |
| head, which guarantees an order 0 allocation each time. |
| |
| Signed-off-by: Jason Wang <jasowang@redhat.com> |
| Cc: Stefan Hajnoczi <stefanha@redhat.com> |
| Cc: Michael S. Tsirkin <mst@redhat.com> |
| Signed-off-by: David S. Miller <davem@davemloft.net> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| --- |
| drivers/net/macvtap.c | 8 +++++++- |
| 1 file changed, 7 insertions(+), 1 deletion(-) |
| |
| --- a/drivers/net/macvtap.c |
| +++ b/drivers/net/macvtap.c |
| @@ -661,6 +661,7 @@ static ssize_t macvtap_get_user(struct m |
| const struct iovec *iv, unsigned long total_len, |
| size_t count, int noblock) |
| { |
| + int good_linear = SKB_MAX_HEAD(NET_IP_ALIGN); |
| struct sk_buff *skb; |
| struct macvlan_dev *vlan; |
| unsigned long len = total_len; |
| @@ -703,6 +704,8 @@ static ssize_t macvtap_get_user(struct m |
| |
| if (m && m->msg_control && sock_flag(&q->sk, SOCK_ZEROCOPY)) { |
| copylen = vnet_hdr.hdr_len ? vnet_hdr.hdr_len : GOODCOPY_LEN; |
| + if (copylen > good_linear) |
| + copylen = good_linear; |
| linear = copylen; |
| if (iov_pages(iv, vnet_hdr_len + copylen, count) |
| <= MAX_SKB_FRAGS) |
| @@ -711,7 +714,10 @@ static ssize_t macvtap_get_user(struct m |
| |
| if (!zerocopy) { |
| copylen = len; |
| - linear = vnet_hdr.hdr_len; |
| + if (vnet_hdr.hdr_len > good_linear) |
| + linear = good_linear; |
| + else |
| + linear = vnet_hdr.hdr_len; |
| } |
| |
| skb = macvtap_alloc_skb(&q->sk, NET_IP_ALIGN, copylen, |