From 217e6fa24ce28ec87fca8da93c9016cb78028612 Mon Sep 17 00:00:00 2001 From: Willem de Bruijn Date: Tue, 7 Feb 2017 15:57:20 -0500 Subject: net: introduce device min_header_len The stack must not pass packets to device drivers that are shorter than the minimum link layer header length. Previously, packet sockets would drop packets smaller than or equal to dev->hard_header_len, but this has false positives. Zero length payload is used over Ethernet. Other link layer protocols support variable length headers. Support for validation of these protocols removed the min length check for all protocols. Introduce an explicit dev->min_header_len parameter and drop all packets below this value. Initially, set it to non-zero only for Ethernet and loopback. Other protocols can follow in a patch to net-next. Fixes: 9ed988cd5915 ("packet: validate variable length ll headers") Reported-by: Sowmini Varadhan Signed-off-by: Willem de Bruijn Acked-by: Eric Dumazet Acked-by: Sowmini Varadhan Signed-off-by: David S. Miller --- drivers/net/loopback.c | 1 + include/linux/netdevice.h | 4 ++++ net/ethernet/eth.c | 1 + 3 files changed, 6 insertions(+) diff --git a/drivers/net/loopback.c b/drivers/net/loopback.c index 1e05b7c2d157..0844f8496413 100644 --- a/drivers/net/loopback.c +++ b/drivers/net/loopback.c @@ -164,6 +164,7 @@ static void loopback_setup(struct net_device *dev) { dev->mtu = 64 * 1024; dev->hard_header_len = ETH_HLEN; /* 14 */ + dev->min_header_len = ETH_HLEN; /* 14 */ dev->addr_len = ETH_ALEN; /* 6 */ dev->type = ARPHRD_LOOPBACK; /* 0x0001*/ dev->flags = IFF_LOOPBACK; diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h index 70ad0291d517..27914672602d 100644 --- a/include/linux/netdevice.h +++ b/include/linux/netdevice.h @@ -1511,6 +1511,7 @@ enum netdev_priv_flags { * @max_mtu: Interface Maximum MTU value * @type: Interface hardware type * @hard_header_len: Maximum hardware header length. + * @min_header_len: Minimum hardware header length * * @needed_headroom: Extra headroom the hardware may need, but not in all * cases can this be guaranteed @@ -1728,6 +1729,7 @@ struct net_device { unsigned int max_mtu; unsigned short type; unsigned short hard_header_len; + unsigned short min_header_len; unsigned short needed_headroom; unsigned short needed_tailroom; @@ -2694,6 +2696,8 @@ static inline bool dev_validate_header(const struct net_device *dev, { if (likely(len >= dev->hard_header_len)) return true; + if (len < dev->min_header_len) + return false; if (capable(CAP_SYS_RAWIO)) { memset(ll_header + len, 0, dev->hard_header_len - len); diff --git a/net/ethernet/eth.c b/net/ethernet/eth.c index 8c5a479681ca..516c87e75de7 100644 --- a/net/ethernet/eth.c +++ b/net/ethernet/eth.c @@ -356,6 +356,7 @@ void ether_setup(struct net_device *dev) dev->header_ops = ð_header_ops; dev->type = ARPHRD_ETHER; dev->hard_header_len = ETH_HLEN; + dev->min_header_len = ETH_HLEN; dev->mtu = ETH_DATA_LEN; dev->min_mtu = ETH_MIN_MTU; dev->max_mtu = ETH_DATA_LEN; -- cgit v1.2.3 From 57031eb794906eea4e1c7b31dc1e2429c0af0c66 Mon Sep 17 00:00:00 2001 From: Willem de Bruijn Date: Tue, 7 Feb 2017 15:57:21 -0500 Subject: packet: round up linear to header len 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 Signed-off-by: Willem de Bruijn Acked-by: Eric Dumazet Signed-off-by: David S. Miller --- net/packet/af_packet.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c index 3d555c79a7b5..d56ee46b11fc 100644 --- a/net/packet/af_packet.c +++ b/net/packet/af_packet.c @@ -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; -- cgit v1.2.3