netdev - Re: [PATCH net] net: avoid race between device unregistration and set

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Message-ID: <173693399736.5893.16178689571036969424@kwain>
Date: Wed, 15 Jan 2025 10:39:57 +0100
From: Antoine Tenart <atenart@...nel.org>
To: Jakub Kicinski <kuba@...nel.org>
Cc: davem@...emloft.net, pabeni@...hat.com, edumazet@...gle.com, netdev@...r.kernel.org, Edward Cree <ecree.xilinx@...il.com>
Subject: Re: [PATCH net] net: avoid race between device unregistration and set_channels

Quoting Jakub Kicinski (2025-01-14 20:24:01)
> On Mon, 13 Jan 2025 17:18:40 +0100 Antoine Tenart wrote:
> > This is because unregister_netdevice_many_notify might run before
> > set_channels (both are under rtnl). 
> 
> But that is very bad, not at all sane. The set call should not proceed
> once dismantle begins.
> 
> How about this?
> 
> diff --git a/net/ethtool/netlink.c b/net/ethtool/netlink.c index 849c98e637c6..913c8e329a06 100644
> --- a/net/ethtool/netlink.c
> +++ b/net/ethtool/netlink.c
> @@ -90,7 +90,7 @@ int ethnl_ops_begin(struct net_device *dev)
>                 pm_runtime_get_sync(dev->dev.parent);
>  
>         if (!netif_device_present(dev) ||
> -           dev->reg_state == NETREG_UNREGISTERING) {
> +           dev->reg_state > NETREG_REGISTERED) {
>                 ret = -ENODEV;
>                 goto err;
>         }

That looks better, I'll send a v2 with this. Now I recall adding the
above for a similar issue...

This makes me think we should do the same in the trylock/restart_syscall
series as this will also allow calls to run after dismantle begins. It
also might be time to make dev_isalive available and use it outside of
net-sysfs.

Thanks!
Antoine