Merge branch 'net-fix-bugs-in-device-netns-move-and-rename'

Jakub Kicinski says:

====================
net: fix bugs in device netns-move and rename

Daniel reported issues with the uevents generated during netdev
namespace move, if the netdev is getting renamed at the same time.

While the issue that he actually cares about is not fixed here,
there is a bunch of seemingly obvious other bugs in this code.
Fix the purely networking bugs while the discussion around
the uevent fix is still ongoing.
====================

Link: https://lore.kernel.org/r/20231018013817.2391509-1-kuba@kernel.org
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

Author: Paolo Abeni

net/core/dev.c

@@ -345,7 +345,6 @@ int netdev_name_node_alt_create(struct net_device *dev, const char *name)
 static void __netdev_name_node_alt_destroy(struct netdev_name_node *name_node)
 {
 	list_del(&name_node->list);
-	netdev_name_node_del(name_node);
 	kfree(name_node->name);
 	netdev_name_node_free(name_node);
 }
@@ -364,6 +363,8 @@ int netdev_name_node_alt_destroy(struct net_device *dev, const char *name)
 	if (name_node == dev->name_node || name_node->dev != dev)
 		return -EINVAL;
 
+	netdev_name_node_del(name_node);
+	synchronize_rcu();
 	__netdev_name_node_alt_destroy(name_node);
 
 	return 0;
@@ -380,6 +381,7 @@ static void netdev_name_node_alt_flush(struct net_device *dev)
 /* Device list insertion */
 static void list_netdevice(struct net_device *dev)
 {
+	struct netdev_name_node *name_node;
 	struct net *net = dev_net(dev);
 
 	ASSERT_RTNL();
@@ -390,6 +392,10 @@ static void list_netdevice(struct net_device *dev)
 	hlist_add_head_rcu(&dev->index_hlist,
 			   dev_index_hash(net, dev->ifindex));
 	write_unlock(&dev_base_lock);
+
+	netdev_for_each_altname(dev, name_node)
+		netdev_name_node_add(net, name_node);
+
 	/* We reserved the ifindex, this can't fail */
 	WARN_ON(xa_store(&net->dev_by_index, dev->ifindex, dev, GFP_KERNEL));
 
@@ -401,12 +407,16 @@ static void list_netdevice(struct net_device *dev)
  */
 static void unlist_netdevice(struct net_device *dev, bool lock)
 {
+	struct netdev_name_node *name_node;
 	struct net *net = dev_net(dev);
 
 	ASSERT_RTNL();
 
 	xa_erase(&net->dev_by_index, dev->ifindex);
 
+	netdev_for_each_altname(dev, name_node)
+		netdev_name_node_del(name_node);
+
 	/* Unlink dev from the device chain */
 	if (lock)
 		write_lock(&dev_base_lock);
@@ -1086,7 +1096,8 @@ static int __dev_alloc_name(struct net *net, const char *name, char *buf)
 
 		for_each_netdev(net, d) {
 			struct netdev_name_node *name_node;
-			list_for_each_entry(name_node, &d->name_node->list, list) {
+
+			netdev_for_each_altname(d, name_node) {
 				if (!sscanf(name_node->name, name, &i))
 					continue;
 				if (i < 0 || i >= max_netdevices)
@@ -1123,6 +1134,26 @@ static int __dev_alloc_name(struct net *net, const char *name, char *buf)
 	return -ENFILE;
 }
 
+static int dev_prep_valid_name(struct net *net, struct net_device *dev,
+			       const char *want_name, char *out_name)
+{
+	int ret;
+
+	if (!dev_valid_name(want_name))
+		return -EINVAL;
+
+	if (strchr(want_name, '%')) {
+		ret = __dev_alloc_name(net, want_name, out_name);
+		return ret < 0 ? ret : 0;
+	} else if (netdev_name_in_use(net, want_name)) {
+		return -EEXIST;
+	} else if (out_name != want_name) {
+		strscpy(out_name, want_name, IFNAMSIZ);
+	}
+
+	return 0;
+}
+
 static int dev_alloc_name_ns(struct net *net,
 			     struct net_device *dev,
 			     const char *name)
@@ -1160,19 +1191,13 @@ EXPORT_SYMBOL(dev_alloc_name);
 static int dev_get_valid_name(struct net *net, struct net_device *dev,
 			      const char *name)
 {
-	BUG_ON(!net);
-
-	if (!dev_valid_name(name))
-		return -EINVAL;
-
-	if (strchr(name, '%'))
-		return dev_alloc_name_ns(net, dev, name);
-	else if (netdev_name_in_use(net, name))
-		return -EEXIST;
-	else if (dev->name != name)
-		strscpy(dev->name, name, IFNAMSIZ);
+	char buf[IFNAMSIZ];
+	int ret;
 
-	return 0;
+	ret = dev_prep_valid_name(net, dev, name, buf);
+	if (ret >= 0)
+		strscpy(dev->name, buf, IFNAMSIZ);
+	return ret;
 }
 
 /**
@@ -11037,7 +11062,9 @@ EXPORT_SYMBOL(unregister_netdev);
 int __dev_change_net_namespace(struct net_device *dev, struct net *net,
 			       const char *pat, int new_ifindex)
 {
+	struct netdev_name_node *name_node;
 	struct net *net_old = dev_net(dev);
+	char new_name[IFNAMSIZ] = {};
 	int err, new_nsid;
 
 	ASSERT_RTNL();
@@ -11064,10 +11091,15 @@ int __dev_change_net_namespace(struct net_device *dev, struct net *net,
 		/* We get here if we can't use the current device name */
 		if (!pat)
 			goto out;
-		err = dev_get_valid_name(net, dev, pat);
+		err = dev_prep_valid_name(net, dev, pat, new_name);
 		if (err < 0)
 			goto out;
 	}
+	/* Check that none of the altnames conflicts. */
+	err = -EEXIST;
+	netdev_for_each_altname(dev, name_node)
+		if (netdev_name_in_use(net, name_node->name))
+			goto out;
 
 	/* Check that new_ifindex isn't used yet. */
 	if (new_ifindex) {
@@ -11135,6 +11167,9 @@ int __dev_change_net_namespace(struct net_device *dev, struct net *net,
 	kobject_uevent(&dev->dev.kobj, KOBJ_ADD);
 	netdev_adjacent_add_links(dev);
 
+	if (new_name[0]) /* Rename the netdev to prepared name */
+		strscpy(dev->name, new_name, IFNAMSIZ);
+
 	/* Fixup kobjects */
 	err = device_rename(&dev->dev, dev->name);
 	WARN_ON(err);

net/core/dev.h

@@ -62,6 +62,9 @@ struct netdev_name_node {
 int netdev_get_name(struct net *net, char *name, int ifindex);
 int dev_change_name(struct net_device *dev, const char *newname);
 
+#define netdev_for_each_altname(dev, namenode)				\
+	list_for_each_entry((namenode), &(dev)->name_node->list, list)
+
 int netdev_name_node_alt_create(struct net_device *dev, const char *name);
 int netdev_name_node_alt_destroy(struct net_device *dev, const char *name);
 

tools/testing/selftests/net/Makefile

@@ -34,6 +34,7 @@ TEST_PROGS += gro.sh
 TEST_PROGS += gre_gso.sh
 TEST_PROGS += cmsg_so_mark.sh
 TEST_PROGS += cmsg_time.sh cmsg_ipv6.sh
+TEST_PROGS += netns-name.sh
 TEST_PROGS += srv6_end_dt46_l3vpn_test.sh
 TEST_PROGS += srv6_end_dt4_l3vpn_test.sh
 TEST_PROGS += srv6_end_dt6_l3vpn_test.sh

tools/testing/selftests/net/netns-name.sh

@@ -0,0 +1,87 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+
+set -o pipefail
+
+NS=netns-name-test
+DEV=dummy-dev0
+DEV2=dummy-dev1
+ALT_NAME=some-alt-name
+
+RET_CODE=0
+
+cleanup() {
+    ip netns del $NS
+}
+
+trap cleanup EXIT
+
+fail() {
+    echo "ERROR: ${1:-unexpected return code} (ret: $_)" >&2
+    RET_CODE=1
+}
+
+ip netns add $NS
+
+#
+# Test basic move without a rename
+#
+ip -netns $NS link add name $DEV type dummy || fail
+ip -netns $NS link set dev $DEV netns 1 ||
+    fail "Can't perform a netns move"
+ip link show dev $DEV >> /dev/null || fail "Device not found after move"
+ip link del $DEV || fail
+
+#
+# Test move with a conflict
+#
+ip link add name $DEV type dummy
+ip -netns $NS link add name $DEV type dummy || fail
+ip -netns $NS link set dev $DEV netns 1 2> /dev/null &&
+    fail "Performed a netns move with a name conflict"
+ip link show dev $DEV >> /dev/null || fail "Device not found after move"
+ip -netns $NS link del $DEV || fail
+ip link del $DEV || fail
+
+#
+# Test move with a conflict and rename
+#
+ip link add name $DEV type dummy
+ip -netns $NS link add name $DEV type dummy || fail
+ip -netns $NS link set dev $DEV netns 1 name $DEV2 ||
+    fail "Can't perform a netns move with rename"
+ip link del $DEV2 || fail
+ip link del $DEV || fail
+
+#
+# Test dup alt-name with netns move
+#
+ip link add name $DEV type dummy || fail
+ip link property add dev $DEV altname $ALT_NAME || fail
+ip -netns $NS link add name $DEV2 type dummy || fail
+ip -netns $NS link property add dev $DEV2 altname $ALT_NAME || fail
+
+ip -netns $NS link set dev $DEV2 netns 1 2> /dev/null &&
+    fail "Moved with alt-name dup"
+
+ip link del $DEV || fail
+ip -netns $NS link del $DEV2 || fail
+
+#
+# Test creating alt-name in one net-ns and using in another
+#
+ip -netns $NS link add name $DEV type dummy || fail
+ip -netns $NS link property add dev $DEV altname $ALT_NAME || fail
+ip -netns $NS link set dev $DEV netns 1 || fail
+ip link show dev $ALT_NAME >> /dev/null || fail "Can't find alt-name after move"
+ip  -netns $NS link show dev $ALT_NAME 2> /dev/null &&
+    fail "Can still find alt-name after move"
+ip link del $DEV || fail
+
+echo -ne "$(basename $0) \t\t\t\t"
+if [ $RET_CODE -eq 0 ]; then
+    echo "[  OK  ]"
+else
+    echo "[ FAIL ]"
+fi
+exit $RET_CODE