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Message-ID: <ZS6yBP+aZk67q8Tc@nanopsycho> Date: Tue, 17 Oct 2023 18:10:44 +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 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. Synchronize_rcu() should be avoided if possible.
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