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linux-next/net/l2tp/l2tp_debugfs.c
Tom Parkin 7b7c0719cd l2tp: avoid deadlock in l2tp stats update
l2tp's u64_stats writers were incorrectly synchronised, making it possible to
deadlock a 64bit machine running a 32bit kernel simply by sending the l2tp
code netlink commands while passing data through l2tp sessions.

Previous discussion on netdev determined that alternative solutions such as
spinlock writer synchronisation or per-cpu data would bring unjustified
overhead, given that most users interested in high volume traffic will likely
be running 64bit kernels on 64bit hardware.

As such, this patch replaces l2tp's use of u64_stats with atomic_long_t,
thereby avoiding the deadlock.

Ref:
http://marc.info/?l=linux-netdev&m=134029167910731&w=2
http://marc.info/?l=linux-netdev&m=134079868111131&w=2

Signed-off-by: Tom Parkin <tparkin@katalix.com>
Signed-off-by: James Chapman <jchapman@katalix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2013-03-20 12:10:39 -04:00

352 lines
9.0 KiB
C

/*
* L2TP subsystem debugfs
*
* Copyright (c) 2010 Katalix Systems Ltd
*
* 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.
*/
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/module.h>
#include <linux/skbuff.h>
#include <linux/socket.h>
#include <linux/hash.h>
#include <linux/l2tp.h>
#include <linux/in.h>
#include <linux/etherdevice.h>
#include <linux/spinlock.h>
#include <linux/debugfs.h>
#include <net/sock.h>
#include <net/ip.h>
#include <net/icmp.h>
#include <net/udp.h>
#include <net/inet_common.h>
#include <net/inet_hashtables.h>
#include <net/tcp_states.h>
#include <net/protocol.h>
#include <net/xfrm.h>
#include <net/net_namespace.h>
#include <net/netns/generic.h>
#include "l2tp_core.h"
static struct dentry *rootdir;
static struct dentry *tunnels;
struct l2tp_dfs_seq_data {
struct net *net;
int tunnel_idx; /* current tunnel */
int session_idx; /* index of session within current tunnel */
struct l2tp_tunnel *tunnel;
struct l2tp_session *session; /* NULL means get next tunnel */
};
static void l2tp_dfs_next_tunnel(struct l2tp_dfs_seq_data *pd)
{
pd->tunnel = l2tp_tunnel_find_nth(pd->net, pd->tunnel_idx);
pd->tunnel_idx++;
}
static void l2tp_dfs_next_session(struct l2tp_dfs_seq_data *pd)
{
pd->session = l2tp_session_find_nth(pd->tunnel, pd->session_idx);
pd->session_idx++;
if (pd->session == NULL) {
pd->session_idx = 0;
l2tp_dfs_next_tunnel(pd);
}
}
static void *l2tp_dfs_seq_start(struct seq_file *m, loff_t *offs)
{
struct l2tp_dfs_seq_data *pd = SEQ_START_TOKEN;
loff_t pos = *offs;
if (!pos)
goto out;
BUG_ON(m->private == NULL);
pd = m->private;
if (pd->tunnel == NULL)
l2tp_dfs_next_tunnel(pd);
else
l2tp_dfs_next_session(pd);
/* NULL tunnel and session indicates end of list */
if ((pd->tunnel == NULL) && (pd->session == NULL))
pd = NULL;
out:
return pd;
}
static void *l2tp_dfs_seq_next(struct seq_file *m, void *v, loff_t *pos)
{
(*pos)++;
return NULL;
}
static void l2tp_dfs_seq_stop(struct seq_file *p, void *v)
{
/* nothing to do */
}
static void l2tp_dfs_seq_tunnel_show(struct seq_file *m, void *v)
{
struct l2tp_tunnel *tunnel = v;
int session_count = 0;
int hash;
struct hlist_node *walk;
struct hlist_node *tmp;
read_lock_bh(&tunnel->hlist_lock);
for (hash = 0; hash < L2TP_HASH_SIZE; hash++) {
hlist_for_each_safe(walk, tmp, &tunnel->session_hlist[hash]) {
struct l2tp_session *session;
session = hlist_entry(walk, struct l2tp_session, hlist);
if (session->session_id == 0)
continue;
session_count++;
}
}
read_unlock_bh(&tunnel->hlist_lock);
seq_printf(m, "\nTUNNEL %u peer %u", tunnel->tunnel_id, tunnel->peer_tunnel_id);
if (tunnel->sock) {
struct inet_sock *inet = inet_sk(tunnel->sock);
#if IS_ENABLED(CONFIG_IPV6)
if (tunnel->sock->sk_family == AF_INET6) {
struct ipv6_pinfo *np = inet6_sk(tunnel->sock);
seq_printf(m, " from %pI6c to %pI6c\n",
&np->saddr, &np->daddr);
} else
#endif
seq_printf(m, " from %pI4 to %pI4\n",
&inet->inet_saddr, &inet->inet_daddr);
if (tunnel->encap == L2TP_ENCAPTYPE_UDP)
seq_printf(m, " source port %hu, dest port %hu\n",
ntohs(inet->inet_sport), ntohs(inet->inet_dport));
}
seq_printf(m, " L2TPv%d, %s\n", tunnel->version,
tunnel->encap == L2TP_ENCAPTYPE_UDP ? "UDP" :
tunnel->encap == L2TP_ENCAPTYPE_IP ? "IP" :
"");
seq_printf(m, " %d sessions, refcnt %d/%d\n", session_count,
tunnel->sock ? atomic_read(&tunnel->sock->sk_refcnt) : 0,
atomic_read(&tunnel->ref_count));
seq_printf(m, " %08x rx %ld/%ld/%ld rx %ld/%ld/%ld\n",
tunnel->debug,
atomic_long_read(&tunnel->stats.tx_packets),
atomic_long_read(&tunnel->stats.tx_bytes),
atomic_long_read(&tunnel->stats.tx_errors),
atomic_long_read(&tunnel->stats.rx_packets),
atomic_long_read(&tunnel->stats.rx_bytes),
atomic_long_read(&tunnel->stats.rx_errors));
if (tunnel->show != NULL)
tunnel->show(m, tunnel);
}
static void l2tp_dfs_seq_session_show(struct seq_file *m, void *v)
{
struct l2tp_session *session = v;
seq_printf(m, " SESSION %u, peer %u, %s\n", session->session_id,
session->peer_session_id,
session->pwtype == L2TP_PWTYPE_ETH ? "ETH" :
session->pwtype == L2TP_PWTYPE_PPP ? "PPP" :
"");
if (session->send_seq || session->recv_seq)
seq_printf(m, " nr %hu, ns %hu\n", session->nr, session->ns);
seq_printf(m, " refcnt %d\n", atomic_read(&session->ref_count));
seq_printf(m, " config %d/%d/%c/%c/%s/%s %08x %u\n",
session->mtu, session->mru,
session->recv_seq ? 'R' : '-',
session->send_seq ? 'S' : '-',
session->data_seq == 1 ? "IPSEQ" :
session->data_seq == 2 ? "DATASEQ" : "-",
session->lns_mode ? "LNS" : "LAC",
session->debug,
jiffies_to_msecs(session->reorder_timeout));
seq_printf(m, " offset %hu l2specific %hu/%hu\n",
session->offset, session->l2specific_type, session->l2specific_len);
if (session->cookie_len) {
seq_printf(m, " cookie %02x%02x%02x%02x",
session->cookie[0], session->cookie[1],
session->cookie[2], session->cookie[3]);
if (session->cookie_len == 8)
seq_printf(m, "%02x%02x%02x%02x",
session->cookie[4], session->cookie[5],
session->cookie[6], session->cookie[7]);
seq_printf(m, "\n");
}
if (session->peer_cookie_len) {
seq_printf(m, " peer cookie %02x%02x%02x%02x",
session->peer_cookie[0], session->peer_cookie[1],
session->peer_cookie[2], session->peer_cookie[3]);
if (session->peer_cookie_len == 8)
seq_printf(m, "%02x%02x%02x%02x",
session->peer_cookie[4], session->peer_cookie[5],
session->peer_cookie[6], session->peer_cookie[7]);
seq_printf(m, "\n");
}
seq_printf(m, " %hu/%hu tx %ld/%ld/%ld rx %ld/%ld/%ld\n",
session->nr, session->ns,
atomic_long_read(&session->stats.tx_packets),
atomic_long_read(&session->stats.tx_bytes),
atomic_long_read(&session->stats.tx_errors),
atomic_long_read(&session->stats.rx_packets),
atomic_long_read(&session->stats.rx_bytes),
atomic_long_read(&session->stats.rx_errors));
if (session->show != NULL)
session->show(m, session);
}
static int l2tp_dfs_seq_show(struct seq_file *m, void *v)
{
struct l2tp_dfs_seq_data *pd = v;
/* display header on line 1 */
if (v == SEQ_START_TOKEN) {
seq_puts(m, "TUNNEL ID, peer ID from IP to IP\n");
seq_puts(m, " L2TPv2/L2TPv3, UDP/IP\n");
seq_puts(m, " sessions session-count, refcnt refcnt/sk->refcnt\n");
seq_puts(m, " debug tx-pkts/bytes/errs rx-pkts/bytes/errs\n");
seq_puts(m, " SESSION ID, peer ID, PWTYPE\n");
seq_puts(m, " refcnt cnt\n");
seq_puts(m, " offset OFFSET l2specific TYPE/LEN\n");
seq_puts(m, " [ cookie ]\n");
seq_puts(m, " [ peer cookie ]\n");
seq_puts(m, " config mtu/mru/rcvseq/sendseq/dataseq/lns debug reorderto\n");
seq_puts(m, " nr/ns tx-pkts/bytes/errs rx-pkts/bytes/errs\n");
goto out;
}
/* Show the tunnel or session context */
if (pd->session == NULL)
l2tp_dfs_seq_tunnel_show(m, pd->tunnel);
else
l2tp_dfs_seq_session_show(m, pd->session);
out:
return 0;
}
static const struct seq_operations l2tp_dfs_seq_ops = {
.start = l2tp_dfs_seq_start,
.next = l2tp_dfs_seq_next,
.stop = l2tp_dfs_seq_stop,
.show = l2tp_dfs_seq_show,
};
static int l2tp_dfs_seq_open(struct inode *inode, struct file *file)
{
struct l2tp_dfs_seq_data *pd;
struct seq_file *seq;
int rc = -ENOMEM;
pd = kzalloc(sizeof(*pd), GFP_KERNEL);
if (pd == NULL)
goto out;
/* Derive the network namespace from the pid opening the
* file.
*/
pd->net = get_net_ns_by_pid(current->pid);
if (IS_ERR(pd->net)) {
rc = PTR_ERR(pd->net);
goto err_free_pd;
}
rc = seq_open(file, &l2tp_dfs_seq_ops);
if (rc)
goto err_free_net;
seq = file->private_data;
seq->private = pd;
out:
return rc;
err_free_net:
put_net(pd->net);
err_free_pd:
kfree(pd);
goto out;
}
static int l2tp_dfs_seq_release(struct inode *inode, struct file *file)
{
struct l2tp_dfs_seq_data *pd;
struct seq_file *seq;
seq = file->private_data;
pd = seq->private;
if (pd->net)
put_net(pd->net);
kfree(pd);
seq_release(inode, file);
return 0;
}
static const struct file_operations l2tp_dfs_fops = {
.owner = THIS_MODULE,
.open = l2tp_dfs_seq_open,
.read = seq_read,
.llseek = seq_lseek,
.release = l2tp_dfs_seq_release,
};
static int __init l2tp_debugfs_init(void)
{
int rc = 0;
rootdir = debugfs_create_dir("l2tp", NULL);
if (IS_ERR(rootdir)) {
rc = PTR_ERR(rootdir);
rootdir = NULL;
goto out;
}
tunnels = debugfs_create_file("tunnels", 0600, rootdir, NULL, &l2tp_dfs_fops);
if (tunnels == NULL)
rc = -EIO;
pr_info("L2TP debugfs support\n");
out:
if (rc)
pr_warn("unable to init\n");
return rc;
}
static void __exit l2tp_debugfs_exit(void)
{
debugfs_remove(tunnels);
debugfs_remove(rootdir);
}
module_init(l2tp_debugfs_init);
module_exit(l2tp_debugfs_exit);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("James Chapman <jchapman@katalix.com>");
MODULE_DESCRIPTION("L2TP debugfs driver");
MODULE_VERSION("1.0");