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Subject[ 67/82] l2tp: fix oops in L2TP IP sockets for connect() AF_UNSPEC case
3.2-stable review patch.  If anyone has any objections, please let me know.

------------------
From: James Chapman <jchapman@katalix.com>

[ Upstream commit c51ce49735c183ef2592db70f918ee698716276b ]

An application may call connect() to disconnect a socket using an
address with family AF_UNSPEC. The L2TP IP sockets were not handling
this case when the socket is not bound and an attempt to connect()
using AF_UNSPEC in such cases would result in an oops. This patch
addresses the problem by protecting the sk_prot->disconnect() call
against trying to unhash the socket before it is bound.

The patch also adds more checks that the sockaddr supplied to bind()
and connect() calls is valid.

RIP: 0010:[<ffffffff82e133b0>] [<ffffffff82e133b0>] inet_unhash+0x50/0xd0
RSP: 0018:ffff88001989be28 EFLAGS: 00010293
Stack:
ffff8800407a8000 0000000000000000 ffff88001989be78 ffffffff82e3a249
ffffffff82e3a050 ffff88001989bec8 ffff88001989be88 ffff8800407a8000
0000000000000010 ffff88001989bec8 ffff88001989bea8 ffffffff82e42639
Call Trace:
[<ffffffff82e3a249>] udp_disconnect+0x1f9/0x290
[<ffffffff82e42639>] inet_dgram_connect+0x29/0x80
[<ffffffff82d012fc>] sys_connect+0x9c/0x100
Reported-by: Sasha Levin <levinsasha928@gmail.com>
Signed-off-by: James Chapman <jchapman@katalix.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
net/l2tp/l2tp_ip.c | 30 ++++++++++++++++++++++++------
1 file changed, 24 insertions(+), 6 deletions(-)
diff --git a/net/l2tp/l2tp_ip.c b/net/l2tp/l2tp_ip.c
index 2a2a3e7..2fbbe1f 100644
--- a/net/l2tp/l2tp_ip.c
+++ b/net/l2tp/l2tp_ip.c
@@ -251,9 +251,16 @@ static int l2tp_ip_bind(struct sock *sk, struct sockaddr *uaddr, int addr_len)
{
struct inet_sock *inet = inet_sk(sk);
struct sockaddr_l2tpip *addr = (struct sockaddr_l2tpip *) uaddr;
- int ret = -EINVAL;
+ int ret;
int chk_addr_ret;

+ if (!sock_flag(sk, SOCK_ZAPPED))
+ return -EINVAL;
+ if (addr_len < sizeof(struct sockaddr_l2tpip))
+ return -EINVAL;
+ if (addr->l2tp_family != AF_INET)
+ return -EINVAL;
+
ret = -EADDRINUSE;
read_lock_bh(&l2tp_ip_lock);
if (__l2tp_ip_bind_lookup(&init_net, addr->l2tp_addr.s_addr, sk->sk_bound_dev_if, addr->l2tp_conn_id))
@@ -283,6 +290,8 @@ static int l2tp_ip_bind(struct sock *sk, struct sockaddr *uaddr, int addr_len)
sk_del_node_init(sk);
write_unlock_bh(&l2tp_ip_lock);
ret = 0;
+ sock_reset_flag(sk, SOCK_ZAPPED);
+
out:
release_sock(sk);

@@ -303,13 +312,14 @@ static int l2tp_ip_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len
__be32 saddr;
int oif, rc;

- rc = -EINVAL;
+ if (sock_flag(sk, SOCK_ZAPPED)) /* Must bind first - autobinding does not work */
+ return -EINVAL;
+
if (addr_len < sizeof(*lsa))
- goto out;
+ return -EINVAL;

- rc = -EAFNOSUPPORT;
if (lsa->l2tp_family != AF_INET)
- goto out;
+ return -EAFNOSUPPORT;

lock_sock(sk);

@@ -363,6 +373,14 @@ out:
return rc;
}

+static int l2tp_ip_disconnect(struct sock *sk, int flags)
+{
+ if (sock_flag(sk, SOCK_ZAPPED))
+ return 0;
+
+ return udp_disconnect(sk, flags);
+}
+
static int l2tp_ip_getname(struct socket *sock, struct sockaddr *uaddr,
int *uaddr_len, int peer)
{
@@ -598,7 +616,7 @@ static struct proto l2tp_ip_prot = {
.close = l2tp_ip_close,
.bind = l2tp_ip_bind,
.connect = l2tp_ip_connect,
- .disconnect = udp_disconnect,
+ .disconnect = l2tp_ip_disconnect,
.ioctl = udp_ioctl,
.destroy = l2tp_ip_destroy_sock,
.setsockopt = ip_setsockopt,



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