From a6c8afd6ef8037c550d646ddb195ad5f0b5bebcf Mon Sep 17 00:00:00 2001 From: Jason Wang Date: Wed, 13 Nov 2013 14:00:40 +0800 Subject: [PATCH] macvtap: limit head length of skb allocated [ 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 Cc: Stefan Hajnoczi Cc: Michael S. Tsirkin Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- drivers/net/macvtap.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/drivers/net/macvtap.c b/drivers/net/macvtap.c index 523d6b2..c70ff7d 100644 --- a/drivers/net/macvtap.c +++ b/drivers/net/macvtap.c @@ -661,6 +661,7 @@ 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; @@ -703,6 +704,8 @@ 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) @@ -711,7 +714,10 @@ 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, -- 2.7.4