macvtap: limit head length of skb allocated (16a3fa28) · Commits · 戴 / test

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>

drivers/net/macvtap.c

+7 −1

Original line number	Diff line number	Diff line
		@@ -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)
		@@ -678,6 +681,9 @@ static ssize_t macvtap_get_user(struct macvtap_queue q, struct msghdr m,

		if (!zerocopy) {
		copylen = len;
		if (vnet_hdr.hdr_len > good_linear)
		linear = good_linear;
		else
		linear = vnet_hdr.hdr_len;
		}

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