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Message-ID: <ZS630zlfkUGEi5vg@nanopsycho> Date: Tue, 17 Oct 2023 18:35:31 +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 Tue, Oct 17, 2023 at 06:10:44PM CEST, jiri@...nulli.us wrote: >Tue, Oct 17, 2023 at 04:52:59PM CEST, kuba@...nel.org wrote: >>On Tue, 17 Oct 2023 09:51:02 +0200 Jiri Pirko wrote: >>> >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. >> >>As I said in the commit message, I prefer the explicit sync. >>Re-inserting the device and taking refs already necessitate it. > >You don't need any ref, just rcu_dereference() the netdev pointer. Oh wait, you are right. Sorry for the fuzz. Reviewed-by: Jiri Pirko <jiri@...dia.com>
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