From: Christoph Hellwig <hch@lst.de>
Date: Thu, 28 May 2020 07:12:13 +0200
Subject: net: add sock_bindtoindex
Patch-mainline: v5.8-rc1
Git-commit: 7594888c782e735f8a7b110094307a4dbe7b3f03
References: bsc#1177028

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

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
Acked-by: Gary Lin <glin@suse.com>
---
 include/net/sock.h        |    1 +
 net/core/sock.c           |   21 +++++++++++++++------
 net/ipv4/udp_tunnel.c     |    4 +---
 net/ipv6/ip6_udp_tunnel.c |    4 +---
 4 files changed, 18 insertions(+), 12 deletions(-)

--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -2676,6 +2676,7 @@ static inline bool sk_dev_equal_l3scope(
 
 void sock_def_readable(struct sock *sk);
 
+int sock_bindtoindex(struct sock *sk, int ifindex);
 void sock_no_linger(struct sock *sk);
 void sock_set_priority(struct sock *sk, u32 priority);
 void sock_set_reuseaddr(struct sock *sk);
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -566,7 +566,7 @@ struct dst_entry *sk_dst_check(struct so
 }
 EXPORT_SYMBOL(sk_dst_check);
 
-static int sock_setbindtodevice_locked(struct sock *sk, int ifindex)
+static int sock_bindtoindex_locked(struct sock *sk, int ifindex)
 {
 	int ret = -ENOPROTOOPT;
 #ifdef CONFIG_NETDEVICES
@@ -594,6 +594,18 @@ out:
 	return ret;
 }
 
+int sock_bindtoindex(struct sock *sk, int ifindex)
+{
+	int ret;
+
+	lock_sock(sk);
+	ret = sock_bindtoindex_locked(sk, ifindex);
+	release_sock(sk);
+
+	return ret;
+}
+EXPORT_SYMBOL(sock_bindtoindex);
+
 static int sock_setbindtodevice(struct sock *sk, char __user *optval,
 				int optlen)
 {
@@ -634,10 +646,7 @@ static int sock_setbindtodevice(struct s
 			goto out;
 	}
 
-	lock_sock(sk);
-	ret = sock_setbindtodevice_locked(sk, index);
-	release_sock(sk);
-
+	return sock_bindtoindex(sk, index);
 out:
 #endif
 
@@ -1197,7 +1206,7 @@ set_rcvbuf:
 		break;
 
 	case SO_BINDTOIFINDEX:
-		ret = sock_setbindtodevice_locked(sk, val);
+		ret = sock_bindtoindex_locked(sk, val);
 		break;
 
 	default:
--- a/net/ipv4/udp_tunnel.c
+++ b/net/ipv4/udp_tunnel.c
@@ -22,9 +22,7 @@ int udp_sock_create4(struct net *net, st
 		goto error;
 
 	if (cfg->bind_ifindex) {
-		err = kernel_setsockopt(sock, SOL_SOCKET, SO_BINDTOIFINDEX,
-					(void *)&cfg->bind_ifindex,
-					sizeof(cfg->bind_ifindex));
+		err = sock_bindtoindex(sock->sk, cfg->bind_ifindex);
 		if (err < 0)
 			goto error;
 	}
--- a/net/ipv6/ip6_udp_tunnel.c
+++ b/net/ipv6/ip6_udp_tunnel.c
@@ -33,9 +33,7 @@ int udp_sock_create6(struct net *net, st
 			goto error;
 	}
 	if (cfg->bind_ifindex) {
-		err = kernel_setsockopt(sock, SOL_SOCKET, SO_BINDTOIFINDEX,
-					(void *)&cfg->bind_ifindex,
-					sizeof(cfg->bind_ifindex));
+		err = sock_bindtoindex(sock->sk, cfg->bind_ifindex);
 		if (err < 0)
 			goto error;
 	}