From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Michael S. Tsirkin" Subject: Re: [PATCH net 2/2] macvtap: correctly linearize skb when zerocopy is used Date: Tue, 9 Jul 2013 13:35:14 +0300 Message-ID: <20130709103514.GC14321@redhat.com> References: <1373364651-10474-1-git-send-email-jasowang@redhat.com> <1373364651-10474-2-git-send-email-jasowang@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: davem@davemloft.net, netdev@vger.kernel.org, linux-kernel@vger.kernel.org To: Jason Wang Return-path: Content-Disposition: inline In-Reply-To: <1373364651-10474-2-git-send-email-jasowang@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On Tue, Jul 09, 2013 at 06:10:51PM +0800, Jason Wang wrote: > Userspace may produce vectors greater than MAX_SKB_FRAGS. When we try to > linearize parts of the skb to let the rest of iov to be fit in > the frags, we need count copylen into linear when calling macvtap_alloc_skb() > instead of partly counting it into data_len. Since this breaks > zerocopy_sg_from_iovec() since its inner counter assumes nr_frags should > be zero at beginning. This cause nr_frags to be increased wrongly without > setting the correct frags. > > This bug were introduced from b92946e2919134ebe2a4083e4302236295ea2a73 > (macvtap: zerocopy: validate vectors before building skb). > > Cc: Michael S. Tsirkin > Signed-off-by: Jason Wang > --- > This patch is needed for stable. > --- > drivers/net/macvtap.c | 3 ++- > 1 files changed, 2 insertions(+), 1 deletions(-) > > diff --git a/drivers/net/macvtap.c b/drivers/net/macvtap.c > index f2c4a3b..b213020 100644 > --- a/drivers/net/macvtap.c > +++ b/drivers/net/macvtap.c > @@ -770,7 +770,8 @@ static ssize_t macvtap_get_user(struct macvtap_queue *q, struct msghdr *m, > copylen = len; > > skb = macvtap_alloc_skb(&q->sk, NET_IP_ALIGN, copylen, > - vnet_hdr.hdr_len, noblock, &err); > + zerocopy ? copylen : vnet_hdr.hdr_len, > + noblock, &err); > if (!skb) > goto err; Same comment as for tun - let's add code for the if statement above. Thanks! > -- > 1.7.1