rxrpc: add rxrpc_sock_set_min_security_level

Add a helper to directly set the RXRPC_MIN_SECURITY_LEVEL sockopt from
kernel space without going through a fake uaccess.

Thanks to David Howells for the documentation updates.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: David Howells <dhowells@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Documentation/networking/rxrpc.rst

@@ -477,7 +477,7 @@ AF_RXRPC sockets support a few socket options at the SOL_RXRPC level:
 	 Encrypted checksum plus packet padded and first eight bytes of packet
 	 encrypted - which includes the actual packet length.
 
-     (c) RXRPC_SECURITY_ENCRYPTED
+     (c) RXRPC_SECURITY_ENCRYPT
 
 	 Encrypted checksum plus entire packet padded and encrypted, including
 	 actual packet length.
@@ -578,7 +578,7 @@ A client would issue an operation by:
      This issues a request_key() to get the key representing the security
      context.  The minimum security level can be set::
 
-	unsigned int sec = RXRPC_SECURITY_ENCRYPTED;
+	unsigned int sec = RXRPC_SECURITY_ENCRYPT;
 	setsockopt(client, SOL_RXRPC, RXRPC_MIN_SECURITY_LEVEL,
 		   &sec, sizeof(sec));
 
@@ -1090,6 +1090,15 @@ The kernel interface functions are as follows:
      jiffies).  In the event of the timeout occurring, the call will be
      aborted and -ETIME or -ETIMEDOUT will be returned.
 
+ (#) Apply the RXRPC_MIN_SECURITY_LEVEL sockopt to a socket from within in the
+     kernel::
+
+       int rxrpc_sock_set_min_security_level(struct sock *sk,
+					     unsigned int val);
+
+     This specifies the minimum security level required for calls on this
+     socket.
+
 
 Configurable Parameters
 =======================

fs/afs/rxrpc.c

@@ -37,7 +37,6 @@ int afs_open_socket(struct afs_net *net)
 {
 	struct sockaddr_rxrpc srx;
 	struct socket *socket;
-	unsigned int min_level;
 	int ret;
 
 	_enter("");
@@ -57,9 +56,8 @@ int afs_open_socket(struct afs_net *net)
 	srx.transport.sin6.sin6_family	= AF_INET6;
 	srx.transport.sin6.sin6_port	= htons(AFS_CM_PORT);
 
-	min_level = RXRPC_SECURITY_ENCRYPT;
-	ret = kernel_setsockopt(socket, SOL_RXRPC, RXRPC_MIN_SECURITY_LEVEL,
-				(void *)&min_level, sizeof(min_level));
+	ret = rxrpc_sock_set_min_security_level(socket->sk,
+						RXRPC_SECURITY_ENCRYPT);
 	if (ret < 0)
 		goto error_2;
 

include/net/af_rxrpc.h

@@ -72,4 +72,6 @@ bool rxrpc_kernel_call_is_complete(struct rxrpc_call *);
 void rxrpc_kernel_set_max_life(struct socket *, struct rxrpc_call *,
 			       unsigned long);
 
+int rxrpc_sock_set_min_security_level(struct sock *sk, unsigned int val);
+
 #endif /* _NET_RXRPC_H */

net/rxrpc/af_rxrpc.c

@@ -571,6 +571,19 @@ static int rxrpc_sendmsg(struct socket *sock, struct msghdr *m, size_t len)
 	return ret;
 }
 
+int rxrpc_sock_set_min_security_level(struct sock *sk, unsigned int val)
+{
+	if (sk->sk_state != RXRPC_UNBOUND)
+		return -EISCONN;
+	if (val > RXRPC_SECURITY_MAX)
+		return -EINVAL;
+	lock_sock(sk);
+	rxrpc_sk(sk)->min_sec_level = val;
+	release_sock(sk);
+	return 0;
+}
+EXPORT_SYMBOL(rxrpc_sock_set_min_security_level);
+
 /*
  * set RxRPC socket options
  */