netdev - Re: [PATCH net] net: devlink: fix UAF in devlink_compat_running

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Date:   Wed, 23 Nov 2022 09:50:17 +0800
From:   Yang Yingliang <yangyingliang@...wei.com>
To:     Jakub Kicinski <kuba@...nel.org>, Leon Romanovsky <leon@...nel.org>
CC:     <netdev@...r.kernel.org>, <jiri@...dia.com>, <davem@...emloft.net>,
        <edumazet@...gle.com>, <pabeni@...hat.com>
Subject: Re: [PATCH net] net: devlink: fix UAF in
 devlink_compat_running_version()


On 2022/11/23 4:27, Jakub Kicinski wrote:
> On Tue, 22 Nov 2022 21:04:29 +0200 Leon Romanovsky wrote:
>>>> Please fix nsim instead of devlink.
>>> I think if devlink is not registered, it can not be get and used, but there
>>> is no API for driver to check this, can I introduce a new helper name
>>> devlink_is_registered() for driver using.
>> There is no need in such API as driver calls to devlink_register() and
>> as such it knows when devlink is registered.
>>
>> This UAF is nsim specific issue. Real devices have single .probe()
>> routine with serialized registration flow. None of them will use
>> devlink_is_registered() call.
> Agreed, the fix is to move the register call back.
> Something along the lines of the untested patch below?
> Yang Yingliang would you be able to turn that into a real patch?
OK.

Thanks,
Yang
>
> diff --git a/drivers/net/netdevsim/dev.c b/drivers/net/netdevsim/dev.c
> index e14686594a71..26602d5fe0a2 100644
> --- a/drivers/net/netdevsim/dev.c
> +++ b/drivers/net/netdevsim/dev.c
> @@ -1566,12 +1566,15 @@ int nsim_drv_probe(struct nsim_bus_dev *nsim_bus_dev)
>   	err = devlink_params_register(devlink, nsim_devlink_params,
>   				      ARRAY_SIZE(nsim_devlink_params));
>   	if (err)
> -		goto err_dl_unregister;
> +		goto err_resource_unregister;
>   	nsim_devlink_set_params_init_values(nsim_dev, devlink);
>   
> +	/* here, because params API still expect devlink to be unregistered */
> +	devl_register(devlink);
> +
>   	err = nsim_dev_dummy_region_init(nsim_dev, devlink);
>   	if (err)
> -		goto err_params_unregister;
> +		goto err_dl_unregister;
>   
>   	err = nsim_dev_traps_init(devlink);
>   	if (err)
> @@ -1610,7 +1613,6 @@ int nsim_drv_probe(struct nsim_bus_dev *nsim_bus_dev)
>   	nsim_dev->esw_mode = DEVLINK_ESWITCH_MODE_LEGACY;
>   	devlink_set_features(devlink, DEVLINK_F_RELOAD);
>   	devl_unlock(devlink);
> -	devlink_register(devlink);
>   	return 0;
>   
>   err_hwstats_exit:
> @@ -1629,10 +1631,11 @@ int nsim_drv_probe(struct nsim_bus_dev *nsim_bus_dev)
>   	nsim_dev_traps_exit(devlink);
>   err_dummy_region_exit:
>   	nsim_dev_dummy_region_exit(nsim_dev);
> -err_params_unregister:
> +err_dl_unregister:
> +	devl_unregister(devlink);
>   	devlink_params_unregister(devlink, nsim_devlink_params,
>   				  ARRAY_SIZE(nsim_devlink_params));
> -err_dl_unregister:
> +err_resource_unregister:
>   	devl_resources_unregister(devlink);
>   err_vfc_free:
>   	kfree(nsim_dev->vfconfigs);
> diff --git a/include/net/devlink.h b/include/net/devlink.h
> index 074a79b8933f..e0f13100fc6b 100644
> --- a/include/net/devlink.h
> +++ b/include/net/devlink.h
> @@ -1593,6 +1593,14 @@ void devlink_set_features(struct devlink *devlink, u64 features);
>   void devlink_register(struct devlink *devlink);
>   void devlink_unregister(struct devlink *devlink);
>   void devlink_free(struct devlink *devlink);
> +
> +void devl_register(struct devlink *devlink)
> +{
> +	devl_assert_locked(devlink);
> +	/* doesn't actually take the instance lock */
> +	devlink_register(devlink);
> +}
> +
>   void devlink_port_init(struct devlink *devlink,
>   		       struct devlink_port *devlink_port);
>   void devlink_port_fini(struct devlink_port *devlink_port);
> .