Re: [PATCH 4/4] net: register debugfs file for net_device refcnt tracker

[Kuniyuki Iwashima <kuniyu@amazon.com>]

From: Jeff Layton <jlayton@kernel.org>
Date: Mon, 14 Apr 2025 10:45:49 -0400
> As a nearly-final step in register_netdevice(), finalize the name in the
> refcount tracker, and register a debugfs file for it.
> 
> Signed-off-by: Jeff Layton <jlayton@kernel.org>
> ---
>  net/core/dev.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/net/core/dev.c b/net/core/dev.c
> index 2f7f5fd9ffec7c0fc219eb6ba57d57a55134186e..db9cac702bb2230ca2bbc2c04ac0a77482c65fc3 100644
> --- a/net/core/dev.c
> +++ b/net/core/dev.c
> @@ -10994,6 +10994,8 @@ int register_netdevice(struct net_device *dev)
>  	    dev->rtnl_link_state == RTNL_LINK_INITIALIZED)
>  		rtmsg_ifinfo(RTM_NEWLINK, dev, ~0U, GFP_KERNEL, 0, NULL);
>  
> +	/* Register debugfs file for the refcount tracker */
> +	ref_tracker_dir_debugfs(&dev->refcnt_tracker, dev->name);

dev->name is not unique across network namespaces, so we should specify
a netns-specific parent dir here.

For example, syzkaller creates a bunch of devices with the same name in
different network namespaces.

Then, we also need to move the file when dev is moved to another netns
in __dev_change_net_namespace().