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packet: round up linear to header len

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Link layer protocols may unconditionally pull headers, as Ethernet
does in eth_type_trans. Ensure that the entire link layer header
always lies in the skb linear segment. tpacket_snd has such a check.
Extend this to packet_snd.

Variable length link layer headers complicate the computation
somewhat. Here skb->len may be smaller than dev->hard_header_len.

Round up the linear length to be at least as long as the smallest of
the two.

Reported-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Willem de Bruijn <willemb@google.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Willem de Bruijn 2017-02-07 15:57:21 -05:00 committed by David S. Miller
parent 217e6fa24c
commit 57031eb794
1 changed files with 4 additions and 3 deletions
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7
net/packet/af_packet.c
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@ -2755,7 +2755,7 @@ static int packet_snd(struct socket *sock, struct msghdr *msg, size_t len)
struct virtio_net_hdr vnet_hdr = { 0 };
int offset = 0;
struct packet_sock *po = pkt_sk(sk);
int hlen, tlen;
int hlen, tlen, linear;
int extra_len = 0;
/*
@ -2816,8 +2816,9 @@ static int packet_snd(struct socket *sock, struct msghdr *msg, size_t len)
err = -ENOBUFS;
hlen = LL_RESERVED_SPACE(dev);
tlen = dev->needed_tailroom;
skb = packet_alloc_skb(sk, hlen + tlen, hlen, len,
__virtio16_to_cpu(vio_le(), vnet_hdr.hdr_len),
linear = __virtio16_to_cpu(vio_le(), vnet_hdr.hdr_len);
linear = max(linear, min_t(int, len, dev->hard_header_len));
skb = packet_alloc_skb(sk, hlen + tlen, hlen, len, linear,
msg->msg_flags & MSG_DONTWAIT, &err);
if (skb == NULL)
goto out_unlock;