Messages in this thread Patch in this message | | | From | Ben Hutchings <> | Date | Tue, 05 May 2015 02:16:39 +0100 | Subject | [PATCH 3.2 196/221] macvtap: limit head length of skb allocated |
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3.2.69-rc1 review patch. If anyone has any objections, please let me know.
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From: Jason Wang <jasowang@redhat.com>
commit 16a3fa28630331e28208872fa5341ce210b901c7 upstream.
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> Signed-off-by: Ben Hutchings <ben@decadent.org.uk> --- drivers/net/macvtap.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-)
--- a/drivers/net/macvtap.c +++ b/drivers/net/macvtap.c @@ -672,6 +672,7 @@ 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; @@ -714,6 +715,8 @@ 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) @@ -722,7 +725,10 @@ 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,
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