linux/net/l2tp/l2tp_core.h
Paolo Abeni b954f94023 l2tp: fix races with ipv4-mapped ipv6 addresses
The l2tp_tunnel_create() function checks for v4mapped ipv6
sockets and cache that flag, so that l2tp core code can
reusing it at xmit time.

If the socket is provided by the userspace, the connection
status of the tunnel sockets can change between the tunnel
creation and the xmit call, so that syzbot is able to
trigger the following splat:

BUG: KASAN: use-after-free in ip6_dst_idev include/net/ip6_fib.h:192
[inline]
BUG: KASAN: use-after-free in ip6_xmit+0x1f76/0x2260
net/ipv6/ip6_output.c:264
Read of size 8 at addr ffff8801bd949318 by task syz-executor4/23448

CPU: 0 PID: 23448 Comm: syz-executor4 Not tainted 4.16.0-rc4+ #65
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Call Trace:
  __dump_stack lib/dump_stack.c:17 [inline]
  dump_stack+0x194/0x24d lib/dump_stack.c:53
  print_address_description+0x73/0x250 mm/kasan/report.c:256
  kasan_report_error mm/kasan/report.c:354 [inline]
  kasan_report+0x23c/0x360 mm/kasan/report.c:412
  __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:433
  ip6_dst_idev include/net/ip6_fib.h:192 [inline]
  ip6_xmit+0x1f76/0x2260 net/ipv6/ip6_output.c:264
  inet6_csk_xmit+0x2fc/0x580 net/ipv6/inet6_connection_sock.c:139
  l2tp_xmit_core net/l2tp/l2tp_core.c:1053 [inline]
  l2tp_xmit_skb+0x105f/0x1410 net/l2tp/l2tp_core.c:1148
  pppol2tp_sendmsg+0x470/0x670 net/l2tp/l2tp_ppp.c:341
  sock_sendmsg_nosec net/socket.c:630 [inline]
  sock_sendmsg+0xca/0x110 net/socket.c:640
  ___sys_sendmsg+0x767/0x8b0 net/socket.c:2046
  __sys_sendmsg+0xe5/0x210 net/socket.c:2080
  SYSC_sendmsg net/socket.c:2091 [inline]
  SyS_sendmsg+0x2d/0x50 net/socket.c:2087
  do_syscall_64+0x281/0x940 arch/x86/entry/common.c:287
  entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x453e69
RSP: 002b:00007f819593cc68 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007f819593d6d4 RCX: 0000000000453e69
RDX: 0000000000000081 RSI: 000000002037ffc8 RDI: 0000000000000004
RBP: 000000000072bea0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 00000000000004c3 R14: 00000000006f72e8 R15: 0000000000000000

This change addresses the issues:
* explicitly checking for TCP_ESTABLISHED for user space provided sockets
* dropping the v4mapped flag usage - it can become outdated - and
  explicitly invoking ipv6_addr_v4mapped() instead

The issue is apparently there since ancient times.

v1 -> v2: (many thanks to Guillaume)
 - with csum issue introduced in v1
 - replace pr_err with pr_debug
 - fix build issue with IPV6 disabled
 - move l2tp_sk_is_v4mapped in l2tp_core.c

v2 -> v3:
 - don't update inet_daddr for v4mapped address, unneeded
 - drop rendundant check at creation time

Reported-and-tested-by: syzbot+92fa328176eb07e4ac1a@syzkaller.appspotmail.com
Fixes: 3557baabf2 ("[L2TP]: PPP over L2TP driver core")
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2018-03-12 15:11:09 -04:00

309 lines
9.2 KiB
C

/*
* L2TP internal definitions.
*
* Copyright (c) 2008,2009 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 version 2 as
* published by the Free Software Foundation.
*/
#include <linux/refcount.h>
#ifndef _L2TP_CORE_H_
#define _L2TP_CORE_H_
/* Just some random numbers */
#define L2TP_TUNNEL_MAGIC 0x42114DDA
#define L2TP_SESSION_MAGIC 0x0C04EB7D
/* Per tunnel, session hash table size */
#define L2TP_HASH_BITS 4
#define L2TP_HASH_SIZE (1 << L2TP_HASH_BITS)
/* System-wide, session hash table size */
#define L2TP_HASH_BITS_2 8
#define L2TP_HASH_SIZE_2 (1 << L2TP_HASH_BITS_2)
struct sk_buff;
struct l2tp_stats {
atomic_long_t tx_packets;
atomic_long_t tx_bytes;
atomic_long_t tx_errors;
atomic_long_t rx_packets;
atomic_long_t rx_bytes;
atomic_long_t rx_seq_discards;
atomic_long_t rx_oos_packets;
atomic_long_t rx_errors;
atomic_long_t rx_cookie_discards;
};
struct l2tp_tunnel;
/* Describes a session. Contains information to determine incoming
* packets and transmit outgoing ones.
*/
struct l2tp_session_cfg {
enum l2tp_pwtype pw_type;
unsigned int data_seq:2; /* data sequencing level
* 0 => none, 1 => IP only,
* 2 => all
*/
unsigned int recv_seq:1; /* expect receive packets with
* sequence numbers? */
unsigned int send_seq:1; /* send packets with sequence
* numbers? */
unsigned int lns_mode:1; /* behave as LNS? LAC enables
* sequence numbers under
* control of LNS. */
int debug; /* bitmask of debug message
* categories */
u16 vlan_id; /* VLAN pseudowire only */
u16 l2specific_type; /* Layer 2 specific type */
u8 cookie[8]; /* optional cookie */
int cookie_len; /* 0, 4 or 8 bytes */
u8 peer_cookie[8]; /* peer's cookie */
int peer_cookie_len; /* 0, 4 or 8 bytes */
int reorder_timeout; /* configured reorder timeout
* (in jiffies) */
int mtu;
int mru;
char *ifname;
};
struct l2tp_session {
int magic; /* should be
* L2TP_SESSION_MAGIC */
long dead;
struct l2tp_tunnel *tunnel; /* back pointer to tunnel
* context */
u32 session_id;
u32 peer_session_id;
u8 cookie[8];
int cookie_len;
u8 peer_cookie[8];
int peer_cookie_len;
u16 l2specific_type;
u16 hdr_len;
u32 nr; /* session NR state (receive) */
u32 ns; /* session NR state (send) */
struct sk_buff_head reorder_q; /* receive reorder queue */
u32 nr_max; /* max NR. Depends on tunnel */
u32 nr_window_size; /* NR window size */
u32 nr_oos; /* NR of last OOS packet */
int nr_oos_count; /* For OOS recovery */
int nr_oos_count_max;
struct hlist_node hlist; /* Hash list node */
refcount_t ref_count;
char name[32]; /* for logging */
char ifname[IFNAMSIZ];
unsigned int data_seq:2; /* data sequencing level
* 0 => none, 1 => IP only,
* 2 => all
*/
unsigned int recv_seq:1; /* expect receive packets with
* sequence numbers? */
unsigned int send_seq:1; /* send packets with sequence
* numbers? */
unsigned int lns_mode:1; /* behave as LNS? LAC enables
* sequence numbers under
* control of LNS. */
int debug; /* bitmask of debug message
* categories */
int reorder_timeout; /* configured reorder timeout
* (in jiffies) */
int reorder_skip; /* set if skip to next nr */
int mtu;
int mru;
enum l2tp_pwtype pwtype;
struct l2tp_stats stats;
struct hlist_node global_hlist; /* Global hash list node */
int (*build_header)(struct l2tp_session *session, void *buf);
void (*recv_skb)(struct l2tp_session *session, struct sk_buff *skb, int data_len);
void (*session_close)(struct l2tp_session *session);
#if IS_ENABLED(CONFIG_L2TP_DEBUGFS)
void (*show)(struct seq_file *m, void *priv);
#endif
uint8_t priv[0]; /* private data */
};
/* Describes the tunnel. It contains info to track all the associated
* sessions so incoming packets can be sorted out
*/
struct l2tp_tunnel_cfg {
int debug; /* bitmask of debug message
* categories */
enum l2tp_encap_type encap;
/* Used only for kernel-created sockets */
struct in_addr local_ip;
struct in_addr peer_ip;
#if IS_ENABLED(CONFIG_IPV6)
struct in6_addr *local_ip6;
struct in6_addr *peer_ip6;
#endif
u16 local_udp_port;
u16 peer_udp_port;
unsigned int use_udp_checksums:1,
udp6_zero_tx_checksums:1,
udp6_zero_rx_checksums:1;
};
struct l2tp_tunnel {
int magic; /* Should be L2TP_TUNNEL_MAGIC */
unsigned long dead;
struct rcu_head rcu;
rwlock_t hlist_lock; /* protect session_hlist */
bool acpt_newsess; /* Indicates whether this
* tunnel accepts new sessions.
* Protected by hlist_lock.
*/
struct hlist_head session_hlist[L2TP_HASH_SIZE];
/* hashed list of sessions,
* hashed by id */
u32 tunnel_id;
u32 peer_tunnel_id;
int version; /* 2=>L2TPv2, 3=>L2TPv3 */
char name[20]; /* for logging */
int debug; /* bitmask of debug message
* categories */
enum l2tp_encap_type encap;
struct l2tp_stats stats;
struct list_head list; /* Keep a list of all tunnels */
struct net *l2tp_net; /* the net we belong to */
refcount_t ref_count;
#ifdef CONFIG_DEBUG_FS
void (*show)(struct seq_file *m, void *arg);
#endif
int (*recv_payload_hook)(struct sk_buff *skb);
void (*old_sk_destruct)(struct sock *);
struct sock *sock; /* Parent socket */
int fd; /* Parent fd, if tunnel socket
* was created by userspace */
struct work_struct del_work;
uint8_t priv[0]; /* private data */
};
struct l2tp_nl_cmd_ops {
int (*session_create)(struct net *net, struct l2tp_tunnel *tunnel,
u32 session_id, u32 peer_session_id,
struct l2tp_session_cfg *cfg);
int (*session_delete)(struct l2tp_session *session);
};
static inline void *l2tp_tunnel_priv(struct l2tp_tunnel *tunnel)
{
return &tunnel->priv[0];
}
static inline void *l2tp_session_priv(struct l2tp_session *session)
{
return &session->priv[0];
}
struct l2tp_tunnel *l2tp_tunnel_get(const struct net *net, u32 tunnel_id);
void l2tp_tunnel_free(struct l2tp_tunnel *tunnel);
struct l2tp_session *l2tp_session_get(const struct net *net,
struct l2tp_tunnel *tunnel,
u32 session_id);
struct l2tp_session *l2tp_session_get_nth(struct l2tp_tunnel *tunnel, int nth);
struct l2tp_session *l2tp_session_get_by_ifname(const struct net *net,
const char *ifname);
struct l2tp_tunnel *l2tp_tunnel_find(const struct net *net, u32 tunnel_id);
struct l2tp_tunnel *l2tp_tunnel_find_nth(const struct net *net, int nth);
int l2tp_tunnel_create(struct net *net, int fd, int version, u32 tunnel_id,
u32 peer_tunnel_id, struct l2tp_tunnel_cfg *cfg,
struct l2tp_tunnel **tunnelp);
void l2tp_tunnel_closeall(struct l2tp_tunnel *tunnel);
void l2tp_tunnel_delete(struct l2tp_tunnel *tunnel);
struct l2tp_session *l2tp_session_create(int priv_size,
struct l2tp_tunnel *tunnel,
u32 session_id, u32 peer_session_id,
struct l2tp_session_cfg *cfg);
int l2tp_session_register(struct l2tp_session *session,
struct l2tp_tunnel *tunnel);
void __l2tp_session_unhash(struct l2tp_session *session);
int l2tp_session_delete(struct l2tp_session *session);
void l2tp_session_free(struct l2tp_session *session);
void l2tp_recv_common(struct l2tp_session *session, struct sk_buff *skb,
unsigned char *ptr, unsigned char *optr, u16 hdrflags,
int length, int (*payload_hook)(struct sk_buff *skb));
int l2tp_session_queue_purge(struct l2tp_session *session);
int l2tp_udp_encap_recv(struct sock *sk, struct sk_buff *skb);
void l2tp_session_set_header_len(struct l2tp_session *session, int version);
int l2tp_xmit_skb(struct l2tp_session *session, struct sk_buff *skb,
int hdr_len);
int l2tp_nl_register_ops(enum l2tp_pwtype pw_type,
const struct l2tp_nl_cmd_ops *ops);
void l2tp_nl_unregister_ops(enum l2tp_pwtype pw_type);
int l2tp_ioctl(struct sock *sk, int cmd, unsigned long arg);
static inline void l2tp_tunnel_inc_refcount(struct l2tp_tunnel *tunnel)
{
refcount_inc(&tunnel->ref_count);
}
static inline void l2tp_tunnel_dec_refcount(struct l2tp_tunnel *tunnel)
{
if (refcount_dec_and_test(&tunnel->ref_count))
l2tp_tunnel_free(tunnel);
}
/* Session reference counts. Incremented when code obtains a reference
* to a session.
*/
static inline void l2tp_session_inc_refcount(struct l2tp_session *session)
{
refcount_inc(&session->ref_count);
}
static inline void l2tp_session_dec_refcount(struct l2tp_session *session)
{
if (refcount_dec_and_test(&session->ref_count))
l2tp_session_free(session);
}
static inline int l2tp_get_l2specific_len(struct l2tp_session *session)
{
switch (session->l2specific_type) {
case L2TP_L2SPECTYPE_DEFAULT:
return 4;
case L2TP_L2SPECTYPE_NONE:
default:
return 0;
}
}
#define l2tp_printk(ptr, type, func, fmt, ...) \
do { \
if (((ptr)->debug) & (type)) \
func(fmt, ##__VA_ARGS__); \
} while (0)
#define l2tp_warn(ptr, type, fmt, ...) \
l2tp_printk(ptr, type, pr_warn, fmt, ##__VA_ARGS__)
#define l2tp_info(ptr, type, fmt, ...) \
l2tp_printk(ptr, type, pr_info, fmt, ##__VA_ARGS__)
#define l2tp_dbg(ptr, type, fmt, ...) \
l2tp_printk(ptr, type, pr_debug, fmt, ##__VA_ARGS__)
#define MODULE_ALIAS_L2TP_PWTYPE(type) \
MODULE_ALIAS("net-l2tp-type-" __stringify(type))
#endif /* _L2TP_CORE_H_ */