From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jason Wang Subject: Re: [PATCH net 2/2] macvtap: correctly linearize skb when zerocopy is used Date: Wed, 10 Jul 2013 13:17:51 +0800 Message-ID: <51DCEE7F.6080608@redhat.com> References: <1373364651-10474-1-git-send-email-jasowang@redhat.com> <1373364651-10474-2-git-send-email-jasowang@redhat.com> <20130709103514.GC14321@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: davem@davemloft.net, netdev@vger.kernel.org, linux-kernel@vger.kernel.org To: "Michael S. Tsirkin" Return-path: In-Reply-To: <20130709103514.GC14321@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On 07/09/2013 06:35 PM, Michael S. Tsirkin wrote: > 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! > Sure, I will post v2. Thanks >> -- >> 1.7.1 > -- > To unsubscribe from this list: send the line "unsubscribe netdev" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html