From 61d46bf979d5cd7c164709a80ad5676a35494aae Mon Sep 17 00:00:00 2001 From: Jason Wang Date: Wed, 10 Jul 2013 13:43:28 +0800 Subject: [PATCH] macvtap: correctly linearize skb when zerocopy is used 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 Acked-by: Michael S. Tsirkin Signed-off-by: David S. Miller --- drivers/net/macvtap.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/drivers/net/macvtap.c b/drivers/net/macvtap.c index f2c4a3b218fc..876c72246ae9 100644 --- a/drivers/net/macvtap.c +++ b/drivers/net/macvtap.c @@ -712,6 +712,7 @@ static ssize_t macvtap_get_user(struct macvtap_queue *q, struct msghdr *m, int vnet_hdr_len = 0; int copylen = 0; bool zerocopy = false; + size_t linear; if (q->flags & IFF_VNET_HDR) { vnet_hdr_len = q->vnet_hdr_sz; @@ -766,11 +767,14 @@ static ssize_t macvtap_get_user(struct macvtap_queue *q, struct msghdr *m, copylen = vnet_hdr.hdr_len; if (!copylen) copylen = GOODCOPY_LEN; - } else + linear = copylen; + } else { copylen = len; + linear = vnet_hdr.hdr_len; + } skb = macvtap_alloc_skb(&q->sk, NET_IP_ALIGN, copylen, - vnet_hdr.hdr_len, noblock, &err); + linear, noblock, &err); if (!skb) goto err; -- 2.20.1