From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jason Wang Subject: [PATCH net 1/2] tuntap: correctly linearize skb when zerocopy is used Date: Tue, 9 Jul 2013 18:10:50 +0800 Message-ID: <1373364651-10474-1-git-send-email-jasowang@redhat.com> Cc: Jason Wang , "Michael S. Tsirkin" To: davem@davemloft.net, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Return-path: Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org 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 tun_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 0690899b4d4501b3505be069b9a687e68ccbe15b (tun: experimental zero copy tx support) Cc: Michael S. Tsirkin Signed-off-by: Jason Wang --- This patch is needed for stable. --- drivers/net/tun.c | 3 ++- 1 files changed, 2 insertions(+), 1 deletions(-) diff --git a/drivers/net/tun.c b/drivers/net/tun.c index 7eab5fc..01d5a86 100644 --- a/drivers/net/tun.c +++ b/drivers/net/tun.c @@ -1109,7 +1109,8 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile, } else copylen = len; - skb = tun_alloc_skb(tfile, align, copylen, gso.hdr_len, noblock); + skb = tun_alloc_skb(tfile, align, copylen, + zerocopy ? copylen : gso.hdr_len, noblock); if (IS_ERR(skb)) { if (PTR_ERR(skb) != -EAGAIN) tun->dev->stats.rx_dropped++; -- 1.7.1