Re: [PATCH net 1/4] ieee802154: Restore initial state on failed device_rename() in cfg802154_switch_netns()

[Kuniyuki Iwashima]

From: Ivan Abramov <i.abramov@xxxxxxxxxxxxxxxxx>
Date: Tue, 25 Mar 2025 17:17:20 +0300
> Currently, the return value of device_rename() is not checked or acted
> upon. There is also a pointless WARN_ON() call in case of an allocation
> failure, since it only leads to useless splats caused by deliberate fault
> injections.
> 
> Since it's possible to roll back the changes made before the
> device_rename() call in case of failure, do it.
> 
> Found by Linux Verification Center (linuxtesting.org) with Syzkaller.
> 
> Fixes: 66e5c2672cd1 ("ieee802154: add netns support")
> Signed-off-by: Ivan Abramov <i.abramov@xxxxxxxxxxxxxxxxx>
> ---
>  net/ieee802154/core.c | 44 +++++++++++++++++++++++--------------------
>  1 file changed, 24 insertions(+), 20 deletions(-)
> 
> diff --git a/net/ieee802154/core.c b/net/ieee802154/core.c
> index 88adb04e4072..f9865eb2c7cf 100644
> --- a/net/ieee802154/core.c
> +++ b/net/ieee802154/core.c
> @@ -233,31 +233,35 @@ int cfg802154_switch_netns(struct cfg802154_registered_device *rdev,
>  		wpan_dev->netdev->netns_local = true;
>  	}
>  
> -	if (err) {
> -		/* failed -- clean up to old netns */
> -		net = wpan_phy_net(&rdev->wpan_phy);
> -
> -		list_for_each_entry_continue_reverse(wpan_dev,
> -						     &rdev->wpan_dev_list,
> -						     list) {
> -			if (!wpan_dev->netdev)
> -				continue;
> -			wpan_dev->netdev->netns_local = false;
> -			err = dev_change_net_namespace(wpan_dev->netdev, net,
> -						       "wpan%d");
> -			WARN_ON(err);
> -			wpan_dev->netdev->netns_local = true;
> -		}
> +	if (err)
> +		goto errout;
>  
> -		return err;
> -	}
> +	err = device_rename(&rdev->wpan_phy.dev, dev_name(&rdev->wpan_phy.dev));
>  
> -	wpan_phy_net_set(&rdev->wpan_phy, net);
> +	if (err)
> +		goto errout;
>  
> -	err = device_rename(&rdev->wpan_phy.dev, dev_name(&rdev->wpan_phy.dev));
> -	WARN_ON(err);
> +	wpan_phy_net_set(&rdev->wpan_phy, net);
>  
>  	return 0;
> +
> +errout:
> +	/* failed -- clean up to old netns */
> +	net = wpan_phy_net(&rdev->wpan_phy);
> +
> +	list_for_each_entry_continue_reverse(wpan_dev,
> +					     &rdev->wpan_dev_list,
> +					     list) {
> +		if (!wpan_dev->netdev)
> +			continue;
> +		wpan_dev->netdev->netns_local = false;
> +		err = dev_change_net_namespace(wpan_dev->netdev, net,
> +					       "wpan%d");
> +		WARN_ON(err);

It's still possible to trigger this with -ENOMEM.

For example, see bitmap_zalloc() in __dev_alloc_name().

Perhaps simply use pr_warn() or net_warn_ratelimited() as do_setlink().

I guess the stack trace from here is not so interesting as it doens't
show where it actually failed.


> +		wpan_dev->netdev->netns_local = true;
> +	}
> +
> +	return err;
>  }
>  
>  void cfg802154_dev_free(struct cfg802154_registered_device *rdev)
> -- 
> 2.39.5