From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jason Wang Subject: [PATCH net 1/2] tuntap: limit head length of skb allocated Date: Tue, 12 Nov 2013 18:02:56 +0800 Message-ID: <1384250577-20330-1-git-send-email-jasowang@redhat.com> Cc: Jason Wang To: davem@davemloft.net, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, mst@redhat.com, stefanha@redhat.com Return-path: Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org 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 --- The patch was needed for stable. --- drivers/net/tun.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/drivers/net/tun.c b/drivers/net/tun.c index 7cb105c..5537b65 100644 --- a/drivers/net/tun.c +++ b/drivers/net/tun.c @@ -954,6 +954,11 @@ static struct sk_buff *tun_alloc_skb(struct tun_file *tfile, struct sock *sk = tfile->socket.sk; struct sk_buff *skb; int err; + int good_linear = SKB_MAX_HEAD(prepad); + + /* Don't use huge linear part */ + if (linear > good_linear) + linear = good_linear; /* Under a page? Don't bother with paged skb. */ if (prepad + len < PAGE_SIZE || !linear) -- 1.8.3.2