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Message-ID: <ZS485sWKKb99KrBx@nanopsycho>
Date: Tue, 17 Oct 2023 09:51:02 +0200
From: Jiri Pirko <jiri@...nulli.us>
To: Jakub Kicinski <kuba@...nel.org>
Cc: davem@...emloft.net, netdev@...r.kernel.org, edumazet@...gle.com,
pabeni@...hat.com
Subject: Re: [PATCH net 3/5] net: avoid UAF on deleted altname
Mon, Oct 16, 2023 at 10:16:55PM CEST, kuba@...nel.org wrote:
>Altnames are accessed under RCU (__dev_get_by_name())
dev_get_by_name_rcu()
>but freed by kfree() with no synchronization point.
>
>Because the name nodes don't hold a reference on the netdevice
>either, take the heavier approach of inserting synchronization
What about to use kfree_rcu() in netdev_name_node_free()
and treat node_name->dev as a rcu pointer instead?
struct net_device *dev_get_by_name_rcu(struct net *net, const char *name)
{
struct netdev_name_node *node_name;
node_name = netdev_name_node_lookup_rcu(net, name);
return node_name ? rcu_deferecence(node_name->dev) : NULL;
}
This would avoid synchronize_rcu() in netdev_name_node_alt_destroy()
Btw, the next patch is smooth with this.
>points. Subsequent patch will remove the one added on device
>deletion path.
>
>Fixes: ff92741270bf ("net: introduce name_node struct to be used in hashlist")
>Signed-off-by: Jakub Kicinski <kuba@...nel.org>
>---
>CC: jiri@...nulli.us
>---
> net/core/dev.c | 7 ++++++-
> 1 file changed, 6 insertions(+), 1 deletion(-)
>
>diff --git a/net/core/dev.c b/net/core/dev.c
>index f4fa2692cf6d..7d5107cd5792 100644
>--- a/net/core/dev.c
>+++ b/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;
>@@ -10937,6 +10938,7 @@ void unregister_netdevice_many_notify(struct list_head *head,
> synchronize_net();
>
> list_for_each_entry(dev, head, unreg_list) {
>+ struct netdev_name_node *name_node;
> struct sk_buff *skb = NULL;
>
> /* Shutdown queueing discipline. */
>@@ -10964,6 +10966,9 @@ void unregister_netdevice_many_notify(struct list_head *head,
> 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);
>
>--
>2.41.0
>
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