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Commit 3dd5c330 authored by Jason Wang's avatar Jason Wang Committed by David S. Miller
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tuntap: 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 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 0690899b
(tun: experimental zero copy tx support)

Cc: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: default avatarJason Wang <jasowang@redhat.com>
Acked-by: default avatarMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 440d57bc

drivers/net/tun.c

+6 −3
Original line number Original line Diff line number Diff line
@@ -1042,7 +1042,7 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile, 
{

{

	struct tun_pi pi = { 0, cpu_to_be16(ETH_P_IP) };

	struct tun_pi pi = { 0, cpu_to_be16(ETH_P_IP) };

	struct sk_buff *skb;

	struct sk_buff *skb;

	size_t len = total_len, align = NET_SKB_PAD;

	size_t len = total_len, align = NET_SKB_PAD, linear;

	struct virtio_net_hdr gso = { 0 };

	struct virtio_net_hdr gso = { 0 };

	int offset = 0;

	int offset = 0;

	int copylen;

	int copylen;
@@ -1106,10 +1106,13 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile, 
			copylen = gso.hdr_len;

			copylen = gso.hdr_len;

		if (!copylen)

		if (!copylen)

			copylen = GOODCOPY_LEN;

			copylen = GOODCOPY_LEN;

	} else

		linear = copylen;

	} else {

		copylen = len;

		copylen = len;

		linear = gso.hdr_len;

	}





	skb = tun_alloc_skb(tfile, align, copylen, gso.hdr_len, noblock);

	skb = tun_alloc_skb(tfile, align, copylen, linear, noblock);

	if (IS_ERR(skb)) {

	if (IS_ERR(skb)) {

		if (PTR_ERR(skb) != -EAGAIN)

		if (PTR_ERR(skb) != -EAGAIN)

			tun->dev->stats.rx_dropped++;

			tun->dev->stats.rx_dropped++;