releases/6.5.9/net-avoid-uaf-on-deleted-altname.patch

From 1a83f4a7c156fa6bbd6b530e89fa3270bf3d9d1b Mon Sep 17 00:00:00 2001
From: Jakub Kicinski <kuba@kernel.org>
Date: Tue, 17 Oct 2023 18:38:15 -0700
Subject: net: avoid UAF on deleted altname

From: Jakub Kicinski <kuba@kernel.org>

commit 1a83f4a7c156fa6bbd6b530e89fa3270bf3d9d1b upstream.

Altnames are accessed under RCU (dev_get_by_name_rcu())
but freed by kfree() with no synchronization point.

Each node has one or two allocations (node and a variable-size
name, sometimes the name is netdev->name). Adding rcu_heads
here is a bit tedious. Besides most code which unlists the names
already has rcu barriers - so take the simpler approach of adding
synchronize_rcu(). Note that the one on the unregistration path
(which matters more) is removed by the next fix.

Fixes: ff92741270bf ("net: introduce name_node struct to be used in hashlist")
Reviewed-by: Jiri Pirko <jiri@nvidia.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 net/core/dev.c |    7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -343,7 +343,6 @@ int netdev_name_node_alt_create(struct n
 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);
 }
@@ -362,6 +361,8 @@ int netdev_name_node_alt_destroy(struct
 	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;
@@ -10838,6 +10839,7 @@ void unregister_netdevice_many_notify(st
 	synchronize_net();
 
 	list_for_each_entry(dev, head, unreg_list) {
+		struct netdev_name_node *name_node;
 		struct sk_buff *skb = NULL;
 
 		/* Shutdown queueing discipline. */
@@ -10865,6 +10867,9 @@ void unregister_netdevice_many_notify(st
 		dev_uc_flush(dev);
 		dev_mc_flush(dev);
 
+		netdev_for_each_altname(dev, name_node)
+			netdev_name_node_del(name_node);
+		synchronize_rcu();
 		netdev_name_node_alt_flush(dev);
 		netdev_name_node_free(dev->name_node);