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Merge branch 'l2tp-fix-races-with-ipv4-mapped-ipv6-addresses'

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Paolo Abeni says:

====================
l2tp: fix races with ipv4-mapped ipv6 addresses

The syzbot reported an l2tp oops that uncovered some races in the l2tp xmit
path and a partially related issue in the generic ipv6 code.

We need to address them separately.

v1 -> v2:
 - add missing fixes tag in patch 1
 - fix several issues in patch 2

v2 -> v3:
 - dropped some unneeded chunks in patch 2
====================

Reviewed-by: Guillaume Nault <g.nault@alphalink.fr>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
David S. Miller 2018-03-12 15:11:20 -04:00
commit 38fbbc9c23
3 changed files with 32 additions and 30 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

21
net/ipv6/datagram.c
View file

@ -146,10 +146,12 @@ int __ip6_datagram_connect(struct sock *sk, struct sockaddr *uaddr,
struct sockaddr_in6 *usin = (struct sockaddr_in6 *) uaddr;
struct inet_sock *inet = inet_sk(sk);
struct ipv6_pinfo *np = inet6_sk(sk);
struct in6_addr *daddr;
struct in6_addr *daddr, old_daddr;
__be32 fl6_flowlabel = 0;
__be32 old_fl6_flowlabel;
__be32 old_dport;
int addr_type;
int err;
__be32 fl6_flowlabel = 0;
if (usin->sin6_family == AF_INET) {
if (__ipv6_only_sock(sk))
@ -238,9 +240,13 @@ int __ip6_datagram_connect(struct sock *sk, struct sockaddr *uaddr,
}
}
/* save the current peer information before updating it */
old_daddr = sk->sk_v6_daddr;
old_fl6_flowlabel = np->flow_label;
old_dport = inet->inet_dport;
sk->sk_v6_daddr = *daddr;
np->flow_label = fl6_flowlabel;
inet->inet_dport = usin->sin6_port;
/*
@ -250,11 +256,12 @@ int __ip6_datagram_connect(struct sock *sk, struct sockaddr *uaddr,
err = ip6_datagram_dst_update(sk, true);
if (err) {
/* Reset daddr and dport so that udp_v6_early_demux()
* fails to find this socket
/* Restore the socket peer info, to keep it consistent with
* the old socket state
*/
memset(&sk->sk_v6_daddr, 0, sizeof(sk->sk_v6_daddr));
inet->inet_dport = 0;
sk->sk_v6_daddr = old_daddr;
np->flow_label = old_fl6_flowlabel;
inet->inet_dport = old_dport;
goto out;
}

38
net/l2tp/l2tp_core.c
View file

@ -111,6 +111,13 @@ struct l2tp_net {
spinlock_t l2tp_session_hlist_lock;
};
#if IS_ENABLED(CONFIG_IPV6)
static bool l2tp_sk_is_v6(struct sock *sk)
{
return sk->sk_family == PF_INET6 &&
!ipv6_addr_v4mapped(&sk->sk_v6_daddr);
}
#endif
static inline struct l2tp_tunnel *l2tp_tunnel(struct sock *sk)
{
@ -1049,7 +1056,7 @@ static int l2tp_xmit_core(struct l2tp_session *session, struct sk_buff *skb,
/* Queue the packet to IP for output */
skb->ignore_df = 1;
#if IS_ENABLED(CONFIG_IPV6)
if (tunnel->sock->sk_family == PF_INET6 && !tunnel->v4mapped)
if (l2tp_sk_is_v6(tunnel->sock))
error = inet6_csk_xmit(tunnel->sock, skb, NULL);
else
#endif
@ -1112,6 +1119,15 @@ int l2tp_xmit_skb(struct l2tp_session *session, struct sk_buff *skb, int hdr_len
goto out_unlock;
}
/* The user-space may change the connection status for the user-space
* provided socket at run time: we must check it under the socket lock
*/
if (tunnel->fd >= 0 && sk->sk_state != TCP_ESTABLISHED) {
kfree_skb(skb);
ret = NET_XMIT_DROP;
goto out_unlock;
}
/* Get routing info from the tunnel socket */
skb_dst_drop(skb);
skb_dst_set(skb, dst_clone(__sk_dst_check(sk, 0)));
@ -1131,7 +1147,7 @@ int l2tp_xmit_skb(struct l2tp_session *session, struct sk_buff *skb, int hdr_len
/* Calculate UDP checksum if configured to do so */
#if IS_ENABLED(CONFIG_IPV6)
if (sk->sk_family == PF_INET6 && !tunnel->v4mapped)
if (l2tp_sk_is_v6(sk))
udp6_set_csum(udp_get_no_check6_tx(sk),
skb, &inet6_sk(sk)->saddr,
&sk->sk_v6_daddr, udp_len);
@ -1511,24 +1527,6 @@ int l2tp_tunnel_create(struct net *net, int fd, int version, u32 tunnel_id, u32
if (cfg != NULL)
tunnel->debug = cfg->debug;
#if IS_ENABLED(CONFIG_IPV6)
if (sk->sk_family == PF_INET6) {
struct ipv6_pinfo *np = inet6_sk(sk);
if (ipv6_addr_v4mapped(&np->saddr) &&
ipv6_addr_v4mapped(&sk->sk_v6_daddr)) {
struct inet_sock *inet = inet_sk(sk);
tunnel->v4mapped = true;
inet->inet_saddr = np->saddr.s6_addr32[3];
inet->inet_rcv_saddr = sk->sk_v6_rcv_saddr.s6_addr32[3];
inet->inet_daddr = sk->sk_v6_daddr.s6_addr32[3];
} else {
tunnel->v4mapped = false;
}
}
#endif
/* Mark socket as an encapsulation socket. See net/ipv4/udp.c */
tunnel->encap = encap;
if (encap == L2TP_ENCAPTYPE_UDP) {

3
net/l2tp/l2tp_core.h
View file

@ -188,9 +188,6 @@ struct l2tp_tunnel {
struct sock *sock; /* Parent socket */
int fd; /* Parent fd, if tunnel socket
* was created by userspace */
#if IS_ENABLED(CONFIG_IPV6)
bool v4mapped;
#endif
struct work_struct del_work;