net: add build-time checks for msg->msg_name size

This is a follow-up patch to f3d3342602f8bc ("net: rework recvmsg
handler msg_name and msg_namelen logic").

DECLARE_SOCKADDR validates that the structure we use for writing the
name information to is not larger than the buffer which is reserved
for msg->msg_name (which is 128 bytes). Also use DECLARE_SOCKADDR
consistently in sendmsg code paths.

Signed-off-by: Steffen Hurrle <steffen@hurrle.net>
Suggested-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Acked-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 4 insertions, 5 deletions

diff --git a/net/l2tp/l2tp_ip.c b/net/l2tp/l2tp_ip.c
index da1a1cee1a08..0b44d855269c 100644
--- a/net/l2tp/l2tp_ip.c
+++ b/net/l2tp/l2tp_ip.c
@@ -403,7 +403,7 @@ static int l2tp_ip_sendmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *m
 
         /* Get and verify the address. */
         if (msg->msg_name) {
-                struct sockaddr_l2tpip *lip = (struct sockaddr_l2tpip *) msg->msg_name;
+                DECLARE_SOCKADDR(struct sockaddr_l2tpip *, lip, msg->msg_name);
                 rc = -EINVAL;
                 if (msg->msg_namelen < sizeof(*lip))
                         goto out;
@@ -512,7 +512,7 @@ static int l2tp_ip_recvmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *m
         struct inet_sock *inet = inet_sk(sk);
         size_t copied = 0;
         int err = -EOPNOTSUPP;
-        struct sockaddr_in *sin = (struct sockaddr_in *)msg->msg_name;
+        DECLARE_SOCKADDR(struct sockaddr_in *, sin, msg->msg_name);
         struct sk_buff *skb;
 
         if (flags & MSG_OOB)
diff --git a/net/l2tp/l2tp_ip6.c b/net/l2tp/l2tp_ip6.c
index 29487a8f7fa0..aab5f74e91e6 100644
--- a/net/l2tp/l2tp_ip6.c
+++ b/net/l2tp/l2tp_ip6.c
@@ -481,8 +481,7 @@ static int l2tp_ip6_sendmsg(struct kiocb *iocb, struct sock *sk,
                             struct msghdr *msg, size_t len)
 {
         struct ipv6_txoptions opt_space;
-        struct sockaddr_l2tpip6 *lsa =
-                (struct sockaddr_l2tpip6 *) msg->msg_name;
+        DECLARE_SOCKADDR(struct sockaddr_l2tpip6 *, lsa, msg->msg_name);
         struct in6_addr *daddr, *final_p, final;
         struct ipv6_pinfo *np = inet6_sk(sk);
         struct ipv6_txoptions *opt = NULL;
@@ -652,7 +651,7 @@ static int l2tp_ip6_recvmsg(struct kiocb *iocb, struct sock *sk,
                             int flags, int *addr_len)
 {
         struct ipv6_pinfo *np = inet6_sk(sk);
-        struct sockaddr_l2tpip6 *lsa = (struct sockaddr_l2tpip6 *)msg->msg_name;
+        DECLARE_SOCKADDR(struct sockaddr_l2tpip6 *, lsa, msg->msg_name);
         size_t copied = 0;
         int err = -EOPNOTSUPP;
         struct sk_buff *skb;