Re: [PATCH net-next] netconsole: register one console per target

[Breno Leitao <leitao@debian.org>]

On Tue, Nov 10, 2026 at 01:42:17AM +0000, netdev-bot+sashiko@kernel.org wrote:
> Thank you for your contribution! Sashiko AI review found 4 potential
> [Severity: High]
> This isn't a bug introduced by this patch, but this patch now registers
> a console right after this lockless store of STATE_ENABLED. Can the store
> overwrite a deactivation done at the same time by a NETDEV_UNREGISTER?
> 
> By the time we get here, netcons_netpoll_setup() has published np.dev,
> dropped the RTNL and waited for a grace period:
> 
> drivers/net/netconsole.c:netcons_netpoll_setup() {
>     ...
> 	err = __netpoll_setup(np, ndev);
> 	if (err)
> 		goto put;
> 	rtnl_unlock();
>     ...
> 	synchronize_rcu();
>     ...
> }
> 
> The target is on target_list during that window, so this sequence looks
> possible:
> 
> enabled_store()                     NETDEV_UNREGISTER
>   netcons_netpoll_setup()
>     rtnl_unlock()
>     synchronize_rcu()               netconsole_netdev_event()
>                                       nt->state = STATE_DEACTIVATED;
>                                       list_move(..., &target_cleanup_list);
>                                     netconsole_process_cleanups_core()
>                                       netcons_release_dev()
>                                         do_netpoll_cleanup()
>                                           np->dev = NULL
>                                       target back on target_list
>   nt->state = STATE_ENABLED;
>   netconsole_register_console()
> 
> The next netconsole_write() would pass the state check and call
> netif_running() with a NULL dev:
> 
> 	if (nt->state != STATE_ENABLED || !netif_running(nt->np.dev))
> 		return;
> 
> process_resume_target() handles this race with the reg_state re-check
> under the RTNL, but enabled_store() has no such check. Does it need one?

I understand that this one got fixed by Gustavo's commit f94b9640bcf22b
("netconsole: finish enabling the target before releasing RTNL")