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Date: Wed, 23 Nov 2022 14:40:24 +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?
>
> 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);
> +
devlink_set_features() called at last in probe() also needs devlink is
not registered.
> 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);
It races with dev_ethtool():
dev_ethtool
devlink_try_get()
nsim_drv_probe
devl_lock()
devl_lock()
devlink_unregister()
devlink_put()
wait_for_completion() <- the refcount
is got in dev_ethtool, it causes ABBA deadlock
> 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);
How about the following changes, it's tested ok in my case:
diff --git a/drivers/net/netdevsim/dev.c b/drivers/net/netdevsim/dev.c
index a7880c7ce94c..0ec4590c26a0 100644
--- a/drivers/net/netdevsim/dev.c
+++ b/drivers/net/netdevsim/dev.c
@@ -1640,6 +1640,8 @@ int nsim_drv_probe(struct nsim_bus_dev *nsim_bus_dev)
kfree(nsim_dev->vfconfigs);
err_devlink_unlock:
devl_unlock(devlink);
+ devl_put(devlink);
+ devl_wait_for_comp(devlink);
devlink_free(devlink);
dev_set_drvdata(&nsim_bus_dev->dev, NULL);
return err;
diff --git a/include/net/devlink.h b/include/net/devlink.h
index ba6b8b094943..dc8ddf942c4d 100644
--- a/include/net/devlink.h
+++ b/include/net/devlink.h
@@ -1563,6 +1563,7 @@ static inline struct devlink *devlink_alloc(const
struct devlink_ops *ops,
void devlink_set_features(struct devlink *devlink, u64 features);
void devlink_register(struct devlink *devlink);
void devlink_unregister(struct devlink *devlink);
+void devl_wait_for_comp(struct devlink *devlink);
void devlink_free(struct devlink *devlink);
void devlink_port_init(struct devlink *devlink,
struct devlink_port *devlink_port);
@@ -1903,4 +1904,6 @@ devlink_compat_switch_id_get(struct net_device *dev,
#endif
+void devl_put(struct devlink *devlink);
+
#endif /* _NET_DEVLINK_H_ */
diff --git a/net/core/devlink.c b/net/core/devlink.c
index 89baa7c0938b..67c78cf37bac 100644
--- a/net/core/devlink.c
+++ b/net/core/devlink.c
@@ -248,6 +248,12 @@ void devlink_put(struct devlink *devlink)
call_rcu(&devlink->rcu, __devlink_put_rcu);
}
+void devl_put(struct devlink *devlink)
+{
+ devlink_put(devlink);
+}
+EXPORT_SYMBOL_GPL(devl_put);
+
struct devlink *__must_check devlink_try_get(struct devlink *devlink)
{
if (refcount_inc_not_zero(&devlink->refcount))
@@ -9788,6 +9794,12 @@ void devlink_unregister(struct devlink *devlink)
}
EXPORT_SYMBOL_GPL(devlink_unregister);
+void devl_wait_for_comp(struct devlink *devlink)
+{
+ wait_for_completion(&devlink->comp);
+}
+EXPORT_SYMBOL_GPL(devl_wait_for_comp);
+
/**
* devlink_free - Free devlink instance resources
*
> .
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