net: remove cmsg restriction from io_uring based send/recvmsg calls

No need to restrict these anymore, as the worker threads are direct
clones of the original task. Hence we know for a fact that we can
support anything that the regular task can.

Since the only user of proto_ops->flags was to flag PROTO_CMSG_DATA_ONLY,
kill the member and the flag definition too.
Signed-off-by: Jens Axboe <axboe@kernel.dk>

include/linux/net.h

@@ -42,8 +42,6 @@ struct net;
 #define SOCK_PASSCRED		3
 #define SOCK_PASSSEC		4
 
-#define PROTO_CMSG_DATA_ONLY	0x0001
-
 #ifndef ARCH_HAS_SOCKET_TYPES
 /**
  * enum sock_type - Socket types
@@ -138,7 +136,6 @@ typedef int (*sk_read_actor_t)(read_descriptor_t *, struct sk_buff *,
 
 struct proto_ops {
 	int		family;
-	unsigned int	flags;
 	struct module	*owner;
 	int		(*release)   (struct socket *sock);
 	int		(*bind)	     (struct socket *sock,

net/ipv4/af_inet.c

@@ -1021,7 +1021,6 @@ static int inet_compat_ioctl(struct socket *sock, unsigned int cmd, unsigned lon
 
 const struct proto_ops inet_stream_ops = {
 	.family		   = PF_INET,
-	.flags		   = PROTO_CMSG_DATA_ONLY,
 	.owner		   = THIS_MODULE,
 	.release	   = inet_release,
 	.bind		   = inet_bind,

net/ipv6/af_inet6.c

@@ -665,7 +665,6 @@ int inet6_recvmsg(struct socket *sock, struct msghdr *msg, size_t size,
 
 const struct proto_ops inet6_stream_ops = {
 	.family		   = PF_INET6,
-	.flags		   = PROTO_CMSG_DATA_ONLY,
 	.owner		   = THIS_MODULE,
 	.release	   = inet6_release,
 	.bind		   = inet6_bind,

net/socket.c

@@ -2411,10 +2411,6 @@ static int ___sys_sendmsg(struct socket *sock, struct user_msghdr __user *msg,
 long __sys_sendmsg_sock(struct socket *sock, struct msghdr *msg,
 			unsigned int flags)
 {
-	/* disallow ancillary data requests from this path */
-	if (msg->msg_control || msg->msg_controllen)
-		return -EINVAL;
-
 	return ____sys_sendmsg(sock, msg, flags, NULL, 0);
 }
 
@@ -2623,12 +2619,6 @@ long __sys_recvmsg_sock(struct socket *sock, struct msghdr *msg,
 			struct user_msghdr __user *umsg,
 			struct sockaddr __user *uaddr, unsigned int flags)
 {
-	if (msg->msg_control || msg->msg_controllen) {
-		/* disallow ancillary data reqs unless cmsg is plain data */
-		if (!(sock->ops->flags & PROTO_CMSG_DATA_ONLY))
-			return -EINVAL;
-	}
-
 	return ____sys_recvmsg(sock, msg, umsg, uaddr, flags, 0);
 }