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macvtap: correctly linearize skb when zerocopy is used

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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 b92946e291
(macvtap: zerocopy: validate vectors before building skb).

Cc: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Jason Wang 2013-07-10 13:43:28 +08:00 committed by David S. Miller
parent 3dd5c3308e
commit 61d46bf979
1 changed files with 6 additions and 2 deletions
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8
drivers/net/macvtap.c
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@ -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;