net,socket: introduce DECLARE_SOCKADDR helper to catch overflow at build time

proto_ops->getname implies copying protocol specific data
into storage unit (particulary to __kernel_sockaddr_storage).
So when we implement new protocol support we should keep such
a detail in mind (which is easy to forget about).

Lets introduce DECLARE_SOCKADDR helper which check if
storage unit is not overfowed at build time.

Eventually inet_getname is switched to use DECLARE_SOCKADDR
(to show example of usage).

Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

3 files changed, 7 insertions, 1 deletions

diff --git a/include/linux/net.h b/include/linux/net.h
index b42bb60fe92f..4da9d571b053 100644
--- a/include/linux/net.h
+++ b/include/linux/net.h
@@ -199,6 +199,9 @@ struct proto_ops {
                                        struct pipe_inode_info *pipe, size_t len, unsigned int flags);
 };
 
+#define DECLARE_SOCKADDR(type, dst, src)        \
+        type dst = ({ __sockaddr_check_size(sizeof(*dst)); (type) src; })
+
 struct net_proto_family {
         int             family;
         int             (*create)(struct net *net, struct socket *sock, int protocol);
diff --git a/include/linux/socket.h b/include/linux/socket.h
index 59966f12990c..7b3aae2052a6 100644
--- a/include/linux/socket.h
+++ b/include/linux/socket.h
@@ -24,6 +24,9 @@ struct __kernel_sockaddr_storage {
 #include <linux/types.h>                /* pid_t                        */
 #include <linux/compiler.h>             /* __user                       */
 
+#define __sockaddr_check_size(size)     \
+        BUILD_BUG_ON(((size) > sizeof(struct __kernel_sockaddr_storage)))
+
 #ifdef __KERNEL__
 # ifdef CONFIG_PROC_FS
 struct seq_file;
diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c
index 04a14b1600ac..538e84d0bcba 100644
--- a/net/ipv4/af_inet.c
+++ b/net/ipv4/af_inet.c
@@ -685,7 +685,7 @@ int inet_getname(struct socket *sock, struct sockaddr *uaddr,
 {
         struct sock *sk         = sock->sk;
         struct inet_sock *inet  = inet_sk(sk);
-        struct sockaddr_in *sin = (struct sockaddr_in *)uaddr;
+        DECLARE_SOCKADDR(struct sockaddr_in *, sin, uaddr);
 
         sin->sin_family = AF_INET;
         if (peer) {