From 58691e5b4f277cf1876dc95654a794b093f88a0f Mon Sep 17 00:00:00 2001 From: Willem de Bruijn Date: Tue, 7 Feb 2017 15:57:20 -0500 Subject: [PATCH] net: introduce device min_header_len [ Upstream commit 217e6fa24ce28ec87fca8da93c9016cb78028612 ] 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 Signed-off-by: Greg Kroah-Hartman --- 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 dc7d970..effcdbf 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 93a6a2c..4035bbe 100644 --- a/include/linux/netdevice.h +++ b/include/linux/netdevice.h @@ -1399,6 +1399,7 @@ enum netdev_priv_flags { * @mtu: Interface 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 @@ -1619,6 +1620,7 @@ struct net_device { unsigned int mtu; unsigned short type; unsigned short hard_header_len; + unsigned short min_header_len; unsigned short needed_headroom; unsigned short needed_tailroom; @@ -2541,6 +2543,8 @@ 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 de85d4e..52dcd41 100644 --- a/net/ethernet/eth.c +++ b/net/ethernet/eth.c @@ -353,6 +353,7 @@ 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->addr_len = ETH_ALEN; dev->tx_queue_len = 1000; /* Ethernet wants good queues */ -- 2.7.4