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macvtap: limit head length of skb allocated

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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.

Cc: Stefan Hajnoczi <stefanha@redhat.com>
Cc: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Jason Wang 2013-11-13 14:00:40 +08:00 committed by David S. Miller
parent 96f8d9ecf2
commit 16a3fa2863
1 changed files with 7 additions and 1 deletions
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8
drivers/net/macvtap.c
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@ -628,6 +628,7 @@ static ssize_t macvtap_get_user(struct macvtap_queue *q, struct msghdr *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;
@ -670,6 +671,8 @@ static ssize_t macvtap_get_user(struct macvtap_queue *q, struct msghdr *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)
@ -678,7 +681,10 @@ static ssize_t macvtap_get_user(struct macvtap_queue *q, struct msghdr *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,