phonet: some signedness bugs

Dan Rosenberg pointed out that there were some signed comparison bugs
in the phonet protocol.

http://marc.info/?l=full-disclosure&m=129424528425330&w=2

The problem is that we check for array overflows but "protocol" is
signed and we don't check for array underflows.  If you have already
have CAP_SYS_ADMIN then you could use the bugs to get root, or someone
could cause an oops by mistake.

Signed-off-by: Dan Carpenter <error27@gmail.com>
Acked-by: Rémi Denis-Courmont <remi.denis-courmont@nokia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/phonet/phonet.h

@@ -107,8 +107,8 @@ struct phonet_protocol {
 	int			sock_type;
 };
 
-int phonet_proto_register(int protocol, struct phonet_protocol *pp);
-void phonet_proto_unregister(int protocol, struct phonet_protocol *pp);
+int phonet_proto_register(unsigned int protocol, struct phonet_protocol *pp);
+void phonet_proto_unregister(unsigned int protocol, struct phonet_protocol *pp);
 
 int phonet_sysctl_init(void);
 void phonet_sysctl_exit(void);

net/phonet/af_phonet.c

@@ -37,7 +37,7 @@
 /* Transport protocol registration */
 static struct phonet_protocol *proto_tab[PHONET_NPROTO] __read_mostly;
 
-static struct phonet_protocol *phonet_proto_get(int protocol)
+static struct phonet_protocol *phonet_proto_get(unsigned int protocol)
 {
 	struct phonet_protocol *pp;
 
@@ -458,7 +458,7 @@ static struct packet_type phonet_packet_type __read_mostly = {
 
 static DEFINE_MUTEX(proto_tab_lock);
 
-int __init_or_module phonet_proto_register(int protocol,
+int __init_or_module phonet_proto_register(unsigned int protocol,
 						struct phonet_protocol *pp)
 {
 	int err = 0;
@@ -481,7 +481,7 @@ int __init_or_module phonet_proto_register(int protocol,
 }
 EXPORT_SYMBOL(phonet_proto_register);
 
-void phonet_proto_unregister(int protocol, struct phonet_protocol *pp)
+void phonet_proto_unregister(unsigned int protocol, struct phonet_protocol *pp)
 {
 	mutex_lock(&proto_tab_lock);
 	BUG_ON(proto_tab[protocol] != pp);