Merge branch 'centralize-netdevice-mtu-bounds-checking'

Jarod Wilson says:

====================
net: centralize net_device MTU bounds checking

While looking into an MTU issue with sfc, I started noticing that almost
every NIC driver with an ndo_change_mtu function implemented almost
exactly the same range checks, and in many cases, that was the only
practical thing their ndo_change_mtu function was doing. Quite a few
drivers have either 68, 64, 60 or 46 as their minimum MTU value checked,
and then various sizes from 1500 to 65535 for their maximum MTU value. We
can remove a whole lot of redundant code here if we simple store min_mtu
and max_mtu in net_device, and check against those in net/core/dev.c's
dev_set_mtu().

This pair of patches looks to introduce centralized MTU range checking
infrastructure, while maintaining compatibility with all existing drivers,
and start to make use of it, converting all eth_change_mtu/ether_setup users
over to this new infra.

Assuming these pass review muster, I've got a ton of follow-on patches to
clean up MTU settings for everything in the kernel with an ndo_change_mtu.

This work is all staged in a (rebasing) git tree here:

https://github.com/jarodwilson/linux-muck

The master branch is based on net-next from Oct 7, and carries these two
patches, plus a ton of follow-on patches to eliminate MTU range checks
and change_mtu functions where possible. All patches were successfully
built across 160 various arch and config combos by the 0-day folks.
(Thanks to Andrew Lunn for the suggestion to get that going).
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

5 files changed, 14 insertions, 8 deletions

diff --git a/net/atm/br2684.c b/net/atm/br2684.c
index aa0047c5c467..c7d82f4e8422 100644
--- a/net/atm/br2684.c
+++ b/net/atm/br2684.c
@@ -620,14 +620,12 @@ error:
 static const struct net_device_ops br2684_netdev_ops = {
 	.ndo_start_xmit 	= br2684_start_xmit,
 	.ndo_set_mac_address	= br2684_mac_addr,
-	.ndo_change_mtu		= eth_change_mtu,
 	.ndo_validate_addr	= eth_validate_addr,
 };
 
 static const struct net_device_ops br2684_netdev_ops_routed = {
 	.ndo_start_xmit 	= br2684_start_xmit,
 	.ndo_set_mac_address	= br2684_mac_addr,
-	.ndo_change_mtu		= eth_change_mtu
 };
 
 static void br2684_setup(struct net_device *netdev)
diff --git a/net/bluetooth/bnep/netdev.c b/net/bluetooth/bnep/netdev.c
index f4fcb4a9d5c1..0f25ddc319e2 100644
--- a/net/bluetooth/bnep/netdev.c
+++ b/net/bluetooth/bnep/netdev.c
@@ -211,7 +211,6 @@ static const struct net_device_ops bnep_netdev_ops = {
 	.ndo_set_rx_mode     = bnep_net_set_mc_list,
 	.ndo_set_mac_address = bnep_net_set_mac_addr,
 	.ndo_tx_timeout      = bnep_net_timeout,
-	.ndo_change_mtu	     = eth_change_mtu,
 
 };
 
diff --git a/net/core/dev.c b/net/core/dev.c
index f1fe26f66458..f376639e8774 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -6499,9 +6499,18 @@ int dev_set_mtu(struct net_device *dev, int new_mtu)
 	if (new_mtu == dev->mtu)
 		return 0;
 
-	/*	MTU must be positive.	 */
-	if (new_mtu < 0)
+	/* MTU must be positive, and in range */
+	if (new_mtu < 0 || new_mtu < dev->min_mtu) {
+		net_err_ratelimited("%s: Invalid MTU %d requested, hw min %d\n",
+				    dev->name, new_mtu, dev->min_mtu);
 		return -EINVAL;
+	}
+
+	if (dev->max_mtu > 0 && new_mtu > dev->max_mtu) {
+		net_err_ratelimited("%s: Invalid MTU %d requested, hw max %d\n",
+				    dev->name, new_mtu, dev->min_mtu);
+		return -EINVAL;
+	}
 
 	if (!netif_device_present(dev))
 		return -ENODEV;
diff --git a/net/ethernet/eth.c b/net/ethernet/eth.c
index 66dff5e3d772..f983c102ebe3 100644
--- a/net/ethernet/eth.c
+++ b/net/ethernet/eth.c
@@ -322,8 +322,7 @@ EXPORT_SYMBOL(eth_mac_addr);
  */
 int eth_change_mtu(struct net_device *dev, int new_mtu)
 {
-	if (new_mtu < 68 || new_mtu > ETH_DATA_LEN)
-		return -EINVAL;
+	netdev_warn(dev, "%s is deprecated\n", __func__);
 	dev->mtu = new_mtu;
 	return 0;
 }
@@ -357,6 +356,8 @@ void ether_setup(struct net_device *dev)
 	dev->type		= ARPHRD_ETHER;
 	dev->hard_header_len 	= ETH_HLEN;
 	dev->mtu		= ETH_DATA_LEN;
+	dev->min_mtu		= ETH_MIN_MTU;
+	dev->max_mtu		= ETH_DATA_LEN;
 	dev->addr_len		= ETH_ALEN;
 	dev->tx_queue_len	= 1000;	/* Ethernet wants good queues */
 	dev->flags		= IFF_BROADCAST|IFF_MULTICAST;
diff --git a/net/irda/irlan/irlan_eth.c b/net/irda/irlan/irlan_eth.c
index d8b7267280c3..8192eaea4ecd 100644
--- a/net/irda/irlan/irlan_eth.c
+++ b/net/irda/irlan/irlan_eth.c
@@ -51,7 +51,6 @@ static const struct net_device_ops irlan_eth_netdev_ops = {
 	.ndo_stop		= irlan_eth_close,
 	.ndo_start_xmit		= irlan_eth_xmit,
 	.ndo_set_rx_mode	= irlan_eth_set_multicast_list,
-	.ndo_change_mtu		= eth_change_mtu,
 	.ndo_validate_addr	= eth_validate_addr,
 };