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Subject[PATCH 4.4 34/65] l2tp: lock socket before checking flags in connect()
Date
From: Guillaume Nault <g.nault@alphalink.fr>

commit 0382a25af3c771a8e4d5e417d1834cbe28c2aaac upstream.

Socket flags aren't updated atomically, so the socket must be locked
while reading the SOCK_ZAPPED flag.

This issue exists for both l2tp_ip and l2tp_ip6. For IPv6, this patch
also brings error handling for __ip6_datagram_connect() failures.

Signed-off-by: Guillaume Nault <g.nault@alphalink.fr>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Giuliano Procida <gprocida@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
include/net/ipv6.h | 2 ++
net/ipv6/datagram.c | 4 +++-
net/l2tp/l2tp_ip.c | 19 ++++++++++++-------
net/l2tp/l2tp_ip6.c | 16 +++++++++++-----
4 files changed, 28 insertions(+), 13 deletions(-)

--- a/include/net/ipv6.h
+++ b/include/net/ipv6.h
@@ -915,6 +915,8 @@ int compat_ipv6_setsockopt(struct sock *
int compat_ipv6_getsockopt(struct sock *sk, int level, int optname,
char __user *optval, int __user *optlen);

+int __ip6_datagram_connect(struct sock *sk, struct sockaddr *addr,
+ int addr_len);
int ip6_datagram_connect(struct sock *sk, struct sockaddr *addr, int addr_len);
int ip6_datagram_connect_v6_only(struct sock *sk, struct sockaddr *addr,
int addr_len);
--- a/net/ipv6/datagram.c
+++ b/net/ipv6/datagram.c
@@ -40,7 +40,8 @@ static bool ipv6_mapped_addr_any(const s
return ipv6_addr_v4mapped(a) && (a->s6_addr32[3] == 0);
}

-static int __ip6_datagram_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len)
+int __ip6_datagram_connect(struct sock *sk, struct sockaddr *uaddr,
+ int addr_len)
{
struct sockaddr_in6 *usin = (struct sockaddr_in6 *) uaddr;
struct inet_sock *inet = inet_sk(sk);
@@ -213,6 +214,7 @@ out:
fl6_sock_release(flowlabel);
return err;
}
+EXPORT_SYMBOL_GPL(__ip6_datagram_connect);

int ip6_datagram_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len)
{
--- a/net/l2tp/l2tp_ip.c
+++ b/net/l2tp/l2tp_ip.c
@@ -321,21 +321,24 @@ static int l2tp_ip_connect(struct sock *
struct sockaddr_l2tpip *lsa = (struct sockaddr_l2tpip *) uaddr;
int rc;

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

if (ipv4_is_multicast(lsa->l2tp_addr.s_addr))
return -EINVAL;

- rc = ip4_datagram_connect(sk, uaddr, addr_len);
- if (rc < 0)
- return rc;
-
lock_sock(sk);

+ /* Must bind first - autobinding does not work */
+ if (sock_flag(sk, SOCK_ZAPPED)) {
+ rc = -EINVAL;
+ goto out_sk;
+ }
+
+ rc = __ip4_datagram_connect(sk, uaddr, addr_len);
+ if (rc < 0)
+ goto out_sk;
+
l2tp_ip_sk(sk)->peer_conn_id = lsa->l2tp_conn_id;

write_lock_bh(&l2tp_ip_lock);
@@ -343,7 +346,9 @@ static int l2tp_ip_connect(struct sock *
sk_add_bind_node(sk, &l2tp_ip_bind_table);
write_unlock_bh(&l2tp_ip_lock);

+out_sk:
release_sock(sk);
+
return rc;
}

--- a/net/l2tp/l2tp_ip6.c
+++ b/net/l2tp/l2tp_ip6.c
@@ -383,9 +383,6 @@ static int l2tp_ip6_connect(struct sock
int addr_type;
int rc;

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

@@ -402,10 +399,18 @@ static int l2tp_ip6_connect(struct sock
return -EINVAL;
}

- rc = ip6_datagram_connect(sk, uaddr, addr_len);
-
lock_sock(sk);

+ /* Must bind first - autobinding does not work */
+ if (sock_flag(sk, SOCK_ZAPPED)) {
+ rc = -EINVAL;
+ goto out_sk;
+ }
+
+ rc = __ip6_datagram_connect(sk, uaddr, addr_len);
+ if (rc < 0)
+ goto out_sk;
+
l2tp_ip6_sk(sk)->peer_conn_id = lsa->l2tp_conn_id;

write_lock_bh(&l2tp_ip6_lock);
@@ -413,6 +418,7 @@ static int l2tp_ip6_connect(struct sock
sk_add_bind_node(sk, &l2tp_ip6_bind_table);
write_unlock_bh(&l2tp_ip6_lock);

+out_sk:
release_sock(sk);

return rc;

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