From: Jason Wang Date: Wed, 13 Nov 2013 06:00:40 +0000 (+0800) Subject: macvtap: limit head length of skb allocated X-Git-Tag: v4.14-rc1~8538^2~50 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=16a3fa28630331e28208872fa5341ce210b901c7;p=platform%2Fkernel%2Flinux-rpi.git macvtap: limit head length of skb allocated 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 Cc: Michael S. Tsirkin Signed-off-by: Jason Wang Signed-off-by: David S. Miller --- diff --git a/drivers/net/macvtap.c b/drivers/net/macvtap.c index 9dccb1e..dc76670 100644 --- a/drivers/net/macvtap.c +++ b/drivers/net/macvtap.c @@ -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,