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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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