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alistair23-linux/net/l2tp/l2tp_core.h
Tom Parkin 80d84ef3ff l2tp: prevent l2tp_tunnel_delete racing with userspace close 
If a tunnel socket is created by userspace, l2tp hooks the socket destructor
in order to clean up resources if userspace closes the socket or crashes.  It
also caches a pointer to the struct sock for use in the data path and in the
netlink interface.

While it is safe to use the cached sock pointer in the data path, where the
skb references keep the socket alive, it is not safe to use it elsewhere as
such access introduces a race with userspace closing the socket.  In
particular, l2tp_tunnel_delete is prone to oopsing if a multithreaded
userspace application closes a socket at the same time as sending a netlink
delete command for the tunnel.

This patch fixes this oops by forcing l2tp_tunnel_delete to explicitly look up
a tunnel socket held by userspace using sockfd_lookup().

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>
2013-01-29 15:43:02 -05:00

301 lines
9.3 KiB
C
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/*
* 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.
*/
#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)
/* Debug message categories for the DEBUG socket option */
enum {
L2TP_MSG_DEBUG = (1 << 0), /* verbose debug (if
* compiled in) */
L2TP_MSG_CONTROL = (1 << 1), /* userspace - kernel
* interface */
L2TP_MSG_SEQ = (1 << 2), /* sequence numbers */
L2TP_MSG_DATA = (1 << 3), /* data packets */
};
struct sk_buff;
struct l2tp_stats {
u64 tx_packets;
u64 tx_bytes;
u64 tx_errors;
u64 rx_packets;
u64 rx_bytes;
u64 rx_seq_discards;
u64 rx_oos_packets;
u64 rx_errors;
u64 rx_cookie_discards;
struct u64_stats_sync syncp;
};
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 offset; /* offset to payload */
u16 l2specific_len; /* Layer 2 specific length */
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 */
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 offset; /* offset from end of L2TP header
to beginning of data */
u16 l2specific_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 */
struct hlist_node hlist; /* Hash list node */
atomic_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);
void (*ref)(struct l2tp_session *session);
void (*deref)(struct l2tp_session *session);
#if defined(CONFIG_L2TP_DEBUGFS) || defined(CONFIG_L2TP_DEBUGFS_MODULE)
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;
};
struct l2tp_tunnel {
int magic; /* Should be L2TP_TUNNEL_MAGIC */
struct rcu_head rcu;
rwlock_t hlist_lock; /* protect session_hlist */
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 */
atomic_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 */
uint8_t priv[0]; /* private data */
};
struct l2tp_nl_cmd_ops {
int (*session_create)(struct net *net, u32 tunnel_id, 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];
}
static inline struct l2tp_tunnel *l2tp_sock_to_tunnel(struct sock *sk)
{
struct l2tp_tunnel *tunnel;
if (sk == NULL)
return NULL;
sock_hold(sk);
tunnel = (struct l2tp_tunnel *)(sk->sk_user_data);
if (tunnel == NULL) {
sock_put(sk);
goto out;
}
BUG_ON(tunnel->magic != L2TP_TUNNEL_MAGIC);
out:
return tunnel;
}
extern struct sock *l2tp_tunnel_sock_lookup(struct l2tp_tunnel *tunnel);
extern void l2tp_tunnel_sock_put(struct sock *sk);
extern struct l2tp_session *l2tp_session_find(struct net *net, struct l2tp_tunnel *tunnel, u32 session_id);
extern struct l2tp_session *l2tp_session_find_nth(struct l2tp_tunnel *tunnel, int nth);
extern struct l2tp_session *l2tp_session_find_by_ifname(struct net *net, char *ifname);
extern struct l2tp_tunnel *l2tp_tunnel_find(struct net *net, u32 tunnel_id);
extern struct l2tp_tunnel *l2tp_tunnel_find_nth(struct net *net, int nth);
extern 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);
extern int l2tp_tunnel_delete(struct l2tp_tunnel *tunnel);
extern 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);
extern int l2tp_session_delete(struct l2tp_session *session);
extern void l2tp_session_free(struct l2tp_session *session);
extern 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));
extern int l2tp_udp_encap_recv(struct sock *sk, struct sk_buff *skb);
extern int l2tp_xmit_skb(struct l2tp_session *session, struct sk_buff *skb, int hdr_len);
extern int l2tp_nl_register_ops(enum l2tp_pwtype pw_type, const struct l2tp_nl_cmd_ops *ops);
extern void l2tp_nl_unregister_ops(enum l2tp_pwtype pw_type);
/* Session reference counts. Incremented when code obtains a reference
* to a session.
*/
static inline void l2tp_session_inc_refcount_1(struct l2tp_session *session)
{
atomic_inc(&session->ref_count);
}
static inline void l2tp_session_dec_refcount_1(struct l2tp_session *session)
{
if (atomic_dec_and_test(&session->ref_count))
l2tp_session_free(session);
}
#ifdef L2TP_REFCNT_DEBUG
#define l2tp_session_inc_refcount(_s) \
do { \
pr_debug("l2tp_session_inc_refcount: %s:%d %s: cnt=%d\n", \
__func__, __LINE__, (_s)->name, \
atomic_read(&_s->ref_count)); \
l2tp_session_inc_refcount_1(_s); \
} while (0)
#define l2tp_session_dec_refcount(_s) \
do { \
pr_debug("l2tp_session_dec_refcount: %s:%d %s: cnt=%d\n", \
__func__, __LINE__, (_s)->name, \
atomic_read(&_s->ref_count)); \
l2tp_session_dec_refcount_1(_s); \
} while (0)
#else
#define l2tp_session_inc_refcount(s) l2tp_session_inc_refcount_1(s)
#define l2tp_session_dec_refcount(s) l2tp_session_dec_refcount_1(s)
#endif
#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__)
#endif /* _L2TP_CORE_H_ */
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