linux/drivers/net/loopback.c

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/*
* INET An implementation of the TCP/IP protocol suite for the LINUX
* operating system. INET is implemented using the BSD Socket
* interface as the means of communication with the user level.
*
* Pseudo-driver for the loopback interface.
*
* Version: @(#)loopback.c 1.0.4b 08/16/93
*
* Authors: Ross Biro
* Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
* Donald Becker, <becker@scyld.com>
*
* Alan Cox : Fixed oddments for NET3.014
* Alan Cox : Rejig for NET3.029 snap #3
* Alan Cox : Fixed NET3.029 bugs and sped up
* Larry McVoy : Tiny tweak to double performance
* Alan Cox : Backed out LMV's tweak - the linux mm
* can't take it...
* Michael Griffith: Don't bother computing the checksums
* on packets received on the loopback
* interface.
* Alexey Kuznetsov: Potential hang under some extreme
* cases removed.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version
* 2 of the License, or (at your option) any later version.
*/
#include <linux/kernel.h>
#include <linux/jiffies.h>
#include <linux/module.h>
#include <linux/interrupt.h>
#include <linux/fs.h>
#include <linux/types.h>
#include <linux/string.h>
#include <linux/socket.h>
#include <linux/errno.h>
#include <linux/fcntl.h>
#include <linux/in.h>
#include <asm/uaccess.h>
#include <asm/io.h>
#include <linux/inet.h>
#include <linux/netdevice.h>
#include <linux/etherdevice.h>
#include <linux/skbuff.h>
#include <linux/ethtool.h>
#include <net/sock.h>
#include <net/checksum.h>
#include <linux/if_ether.h> /* For the statistics structure. */
#include <linux/if_arp.h> /* For ARPHRD_ETHER */
#include <linux/ip.h>
#include <linux/tcp.h>
#include <linux/percpu.h>
#include <net/net_namespace.h>
#include <linux/u64_stats_sync.h>
struct pcpu_lstats {
u64 packets;
u64 bytes;
struct u64_stats_sync syncp;
};
/*
* The higher levels take care of making this non-reentrant (it's
* called with bh's disabled).
*/
static netdev_tx_t loopback_xmit(struct sk_buff *skb,
struct net_device *dev)
{
struct pcpu_lstats *lb_stats;
int len;
skb_orphan(skb);
net: loopback: fix a dst refcounting issue Ben Greear reported crashes in ip_rcv_finish() on a stress test involving many macvlans. We tracked the bug to a dst use after free. ip_rcv_finish() was calling dst->input() and got garbage for dst->input value. It appears the bug is in loopback driver, lacking a skb_dst_force() before calling netif_rx(). As a result, a non refcounted dst, normally protected by a RCU read_lock section, was escaping this section and could be freed before the packet being processed. [<ffffffff813a3c4d>] loopback_xmit+0x64/0x83 [<ffffffff81477364>] dev_hard_start_xmit+0x26c/0x35e [<ffffffff8147771a>] dev_queue_xmit+0x2c4/0x37c [<ffffffff81477456>] ? dev_hard_start_xmit+0x35e/0x35e [<ffffffff8148cfa6>] ? eth_header+0x28/0xb6 [<ffffffff81480f09>] neigh_resolve_output+0x176/0x1a7 [<ffffffff814ad835>] ip_finish_output2+0x297/0x30d [<ffffffff814ad6d5>] ? ip_finish_output2+0x137/0x30d [<ffffffff814ad90e>] ip_finish_output+0x63/0x68 [<ffffffff814ae412>] ip_output+0x61/0x67 [<ffffffff814ab904>] dst_output+0x17/0x1b [<ffffffff814adb6d>] ip_local_out+0x1e/0x23 [<ffffffff814ae1c4>] ip_queue_xmit+0x315/0x353 [<ffffffff814adeaf>] ? ip_send_unicast_reply+0x2cc/0x2cc [<ffffffff814c018f>] tcp_transmit_skb+0x7ca/0x80b [<ffffffff814c3571>] tcp_connect+0x53c/0x587 [<ffffffff810c2f0c>] ? getnstimeofday+0x44/0x7d [<ffffffff810c2f56>] ? ktime_get_real+0x11/0x3e [<ffffffff814c6f9b>] tcp_v4_connect+0x3c2/0x431 [<ffffffff814d6913>] __inet_stream_connect+0x84/0x287 [<ffffffff814d6b38>] ? inet_stream_connect+0x22/0x49 [<ffffffff8108d695>] ? _local_bh_enable_ip+0x84/0x9f [<ffffffff8108d6c8>] ? local_bh_enable+0xd/0x11 [<ffffffff8146763c>] ? lock_sock_nested+0x6e/0x79 [<ffffffff814d6b38>] ? inet_stream_connect+0x22/0x49 [<ffffffff814d6b49>] inet_stream_connect+0x33/0x49 [<ffffffff814632c6>] sys_connect+0x75/0x98 This bug was introduced in linux-2.6.35, in commit 7fee226ad2397b (net: add a noref bit on skb dst) skb_dst_force() is enforced in dev_queue_xmit() for devices having a qdisc. Reported-by: Ben Greear <greearb@candelatech.com> Signed-off-by: Eric Dumazet <edumazet@google.com> Tested-by: Ben Greear <greearb@candelatech.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2013-01-25 07:44:41 +00:00
/* Before queueing this packet to netif_rx(),
* make sure dst is refcounted.
*/
skb_dst_force(skb);
skb->protocol = eth_type_trans(skb, dev);
/* it's OK to use per_cpu_ptr() because BHs are off */
lb_stats = this_cpu_ptr(dev->lstats);
len = skb->len;
if (likely(netif_rx(skb) == NET_RX_SUCCESS)) {
u64_stats_update_begin(&lb_stats->syncp);
lb_stats->bytes += len;
lb_stats->packets++;
u64_stats_update_end(&lb_stats->syncp);
}
return NETDEV_TX_OK;
}
static struct rtnl_link_stats64 *loopback_get_stats64(struct net_device *dev,
struct rtnl_link_stats64 *stats)
{
u64 bytes = 0;
u64 packets = 0;
int i;
for_each_possible_cpu(i) {
const struct pcpu_lstats *lb_stats;
u64 tbytes, tpackets;
unsigned int start;
lb_stats = per_cpu_ptr(dev->lstats, i);
do {
start = u64_stats_fetch_begin_irq(&lb_stats->syncp);
tbytes = lb_stats->bytes;
tpackets = lb_stats->packets;
} while (u64_stats_fetch_retry_irq(&lb_stats->syncp, start));
bytes += tbytes;
packets += tpackets;
}
stats->rx_packets = packets;
stats->tx_packets = packets;
stats->rx_bytes = bytes;
stats->tx_bytes = bytes;
return stats;
}
static u32 always_on(struct net_device *dev)
{
return 1;
}
static const struct ethtool_ops loopback_ethtool_ops = {
.get_link = always_on,
};
static int loopback_dev_init(struct net_device *dev)
{
dev->lstats = netdev_alloc_pcpu_stats(struct pcpu_lstats);
if (!dev->lstats)
return -ENOMEM;
return 0;
}
static void loopback_dev_free(struct net_device *dev)
{
dev_net(dev)->loopback_dev = NULL;
free_percpu(dev->lstats);
free_netdev(dev);
}
static const struct net_device_ops loopback_ops = {
.ndo_init = loopback_dev_init,
.ndo_start_xmit= loopback_xmit,
.ndo_get_stats64 = loopback_get_stats64,
.ndo_set_mac_address = eth_mac_addr,
};
/*
* The loopback device is special. There is only one instance
* per network namespace.
*/
static void loopback_setup(struct net_device *dev)
{
dev->mtu = 64 * 1024;
dev->hard_header_len = ETH_HLEN; /* 14 */
dev->addr_len = ETH_ALEN; /* 6 */
dev->tx_queue_len = 0;
dev->type = ARPHRD_LOOPBACK; /* 0x0001*/
dev->flags = IFF_LOOPBACK;
dev->priv_flags |= IFF_LIVE_ADDR_CHANGE;
netif_keep_dst(dev);
dev->hw_features = NETIF_F_ALL_TSO | NETIF_F_UFO;
dev->features = NETIF_F_SG | NETIF_F_FRAGLIST
| NETIF_F_ALL_TSO
| NETIF_F_UFO
| NETIF_F_HW_CSUM
| NETIF_F_RXCSUM
| NETIF_F_SCTP_CSUM
| NETIF_F_HIGHDMA
| NETIF_F_LLTX
| NETIF_F_NETNS_LOCAL
| NETIF_F_VLAN_CHALLENGED
| NETIF_F_LOOPBACK;
dev->ethtool_ops = &loopback_ethtool_ops;
dev->header_ops = &eth_header_ops;
dev->netdev_ops = &loopback_ops;
dev->destructor = loopback_dev_free;
}
/* Setup and register the loopback device. */
static __net_init int loopback_net_init(struct net *net)
{
struct net_device *dev;
int err;
err = -ENOMEM;
dev = alloc_netdev(0, "lo", NET_NAME_UNKNOWN, loopback_setup);
if (!dev)
goto out;
dev_net_set(dev, net);
err = register_netdev(dev);
if (err)
goto out_free_netdev;
BUG_ON(dev->ifindex != LOOPBACK_IFINDEX);
net->loopback_dev = dev;
return 0;
out_free_netdev:
free_netdev(dev);
out:
if (net_eq(net, &init_net))
panic("loopback: Failed to register netdevice: %d\n", err);
return err;
}
/* Registered in net/core/dev.c */
struct pernet_operations __net_initdata loopback_net_ops = {
.init = loopback_net_init,
};