net: Remove the err argument from sock_from_file

Currently, the sock_from_file prototype takes an "err" pointer that is
either not set or set to -ENOTSOCK IFF the returned socket is NULL. This
makes the error redundant and it is ignored by a few callers.

This patch simplifies the API by letting callers deduce the error based
on whether the returned socket is NULL or not.

Suggested-by: Al Viro <[e-mail]>
Signed-off-by: Florent Revest <[e-mail]>
Signed-off-by: Daniel Borkmann <[e-mail]>
Reviewed-by: KP Singh <[e-mail]>
Link: https://lore.kernel.org/bpf/[e-mail]

fs/eventpoll.c

···
 	unsigned int napi_id;
 	struct socket *sock;
 	struct sock *sk;
-	int err;
 
 	if (!net_busy_loop_on())
 		return;
 
-	sock = sock_from_file(epi->ffd.file, &err);
+	sock = sock_from_file(epi->ffd.file);
 	if (!sock)
 		return;
 

fs/io_uring.c

···
 	unsigned flags;
 	int ret;
 
-	sock = sock_from_file(req->file, &ret);
+	sock = sock_from_file(req->file);
 	if (unlikely(!sock))
-		return ret;
+		return -ENOTSOCK;
 
 	if (req->async_data) {
 		kmsg = req->async_data;
···
 	unsigned flags;
 	int ret;
 
-	sock = sock_from_file(req->file, &ret);
+	sock = sock_from_file(req->file);
 	if (unlikely(!sock))
-		return ret;
+		return -ENOTSOCK;
 
 	ret = import_single_range(WRITE, sr->buf, sr->len, &iov, &msg.msg_iter);
 	if (unlikely(ret))
···
 	unsigned flags;
 	int ret, cflags = 0;
 
-	sock = sock_from_file(req->file, &ret);
+	sock = sock_from_file(req->file);
 	if (unlikely(!sock))
-		return ret;
+		return -ENOTSOCK;
 
 	if (req->async_data) {
 		kmsg = req->async_data;
···
 	unsigned flags;
 	int ret, cflags = 0;
 
-	sock = sock_from_file(req->file, &ret);
+	sock = sock_from_file(req->file);
 	if (unlikely(!sock))
-		return ret;
+		return -ENOTSOCK;
 
 	if (req->flags & REQ_F_BUFFER_SELECT) {
 		kbuf = io_recv_buffer_select(req, !force_nonblock);

include/linux/net.h

···
 int sock_recvmsg(struct socket *sock, struct msghdr *msg, int flags);
 struct file *sock_alloc_file(struct socket *sock, int flags, const char *dname);
 struct socket *sockfd_lookup(int fd, int *err);
-struct socket *sock_from_file(struct file *file, int *err);
+struct socket *sock_from_file(struct file *file);
 #define		     sockfd_put(sock) fput(sock->file)
 int net_ratelimit(void);
 

net/core/netclassid_cgroup.c

···
 
 static int update_classid_sock(const void *v, struct file *file, unsigned n)
 {
-	int err;
 	struct update_classid_context *ctx = (void *)v;
-	struct socket *sock = sock_from_file(file, &err);
+	struct socket *sock = sock_from_file(file);
 
 	if (sock) {
 		spin_lock(&cgroup_sk_update_lock);

net/core/netprio_cgroup.c

···
 
 static int update_netprio(const void *v, struct file *file, unsigned n)
 {
-	int err;
-	struct socket *sock = sock_from_file(file, &err);
+	struct socket *sock = sock_from_file(file);
 	if (sock) {
 		spin_lock(&cgroup_sk_update_lock);
 		sock_cgroup_set_prioidx(&sock->sk->sk_cgrp_data,

net/core/sock.c

···
 void __receive_sock(struct file *file)
 {
 	struct socket *sock;
-	int error;
 
-	/*
-	 * The resulting value of "error" is ignored here since we only
-	 * need to take action when the file is a socket and testing
-	 * "sock" for NULL is sufficient.
-	 */
-	sock = sock_from_file(file, &error);
+	sock = sock_from_file(file);
 	if (sock) {
 		sock_update_netprioidx(&sock->sk->sk_cgrp_data);
 		sock_update_classid(&sock->sk->sk_cgrp_data);

net/socket.c

···
 /**
  *	sock_from_file - Return the &socket bounded to @file.
  *	@file: file
- *	@err: pointer to an error code return
  *
- *	On failure returns %NULL and assigns -ENOTSOCK to @err.
+ *	On failure returns %NULL.
  */
 
-struct socket *sock_from_file(struct file *file, int *err)
+struct socket *sock_from_file(struct file *file)
 {
 	if (file->f_op == &socket_file_ops)
 		return file->private_data;	/* set in sock_map_fd */
 
-	*err = -ENOTSOCK;
 	return NULL;
 }
 EXPORT_SYMBOL(sock_from_file);
···
 		return NULL;
 	}
 
-	sock = sock_from_file(file, err);
-	if (!sock)
+	sock = sock_from_file(file);
+	if (!sock) {
+		*err = -ENOTSOCK;
 		fput(file);
+	}
 	return sock;
 }
 EXPORT_SYMBOL(sockfd_lookup);
···
 
 	*err = -EBADF;
 	if (f.file) {
-		sock = sock_from_file(f.file, err);
+		sock = sock_from_file(f.file);
 		if (likely(sock)) {
 			*fput_needed = f.flags & FDPUT_FPUT;
 			return sock;
 		}
+		*err = -ENOTSOCK;
 		fdput(f);
 	}
 	return NULL;
···
 	if (SOCK_NONBLOCK != O_NONBLOCK && (flags & SOCK_NONBLOCK))
 		flags = (flags & ~SOCK_NONBLOCK) | O_NONBLOCK;
 
-	sock = sock_from_file(file, &err);
-	if (!sock)
+	sock = sock_from_file(file);
+	if (!sock) {
+		err = -ENOTSOCK;
 		goto out;
+	}
 
 	err = -ENFILE;
 	newsock = sock_alloc();
···
 	struct socket *sock;
 	int err;
 
-	sock = sock_from_file(file, &err);
-	if (!sock)
+	sock = sock_from_file(file);
+	if (!sock) {
+		err = -ENOTSOCK;
 		goto out;
+	}
 
 	err =
 	    security_socket_connect(sock, (struct sockaddr *)address, addrlen);