Re: [PATCH net] net: devlink: fix UAF in devlink_compat_running_version()

From: Jiri Pirko <jiri@resnulli.us>
To: Leon Romanovsky <leon@kernel.org>
Cc: Jakub Kicinski <kuba@kernel.org>,
	Ido Schimmel <idosch@idosch.org>,
	Yang Yingliang <yangyingliang@huawei.com>,
	netdev@vger.kernel.org, jiri@nvidia.com, davem@davemloft.net,
	edumazet@google.com, pabeni@redhat.com
Subject: Re: [PATCH net] net: devlink: fix UAF in devlink_compat_running_version()
Date: Thu, 1 Dec 2022 13:20:10 +0100	[thread overview]
Message-ID: <Y4ib+gOo50lpbEWS@nanopsycho> (raw)
In-Reply-To: <Y4h8cvsa+6LT/Yq+@unreal>

Thu, Dec 01, 2022 at 11:05:38AM CET, leon@kernel.org wrote:
>On Thu, Dec 01, 2022 at 09:40:00AM +0100, Jiri Pirko wrote:
>> Wed, Nov 30, 2022 at 08:20:34PM CET, leon@kernel.org wrote:
>> >On Wed, Nov 30, 2022 at 09:20:42AM -0800, Jakub Kicinski wrote:
>> >> On Wed, 30 Nov 2022 18:00:05 +0100 Jiri Pirko wrote:
>> >> > Wed, Nov 30, 2022 at 05:46:59PM CET, kuba@kernel.org wrote:
>> >> > >On Wed, 30 Nov 2022 12:42:39 +0100 Jiri Pirko wrote:  
>> >> > >> **)
>> >> > >> I see. With the change I suggest, meaning doing
>> >> > >> devlink_port_register/unregister() and netdev_register/unregister only
>> >> > >> for registered devlink instance, you don't need this at all. When you
>> >> > >> hit this compat callback, the netdevice is there and therefore devlink
>> >> > >> instance is registered for sure.  
>> >> > >
>> >> > >If you move devlink registration up it has to be under the instance
>> >> > >lock, otherwise we're back to reload problems. That implies unregister
>> >> > >should be under the lock too. But then we can't wait for refs in
>> >> > >unregister. Perhaps I don't understand the suggestion.  
>> >> > 
>> >> > I unlock for register and for the rest of the init I lock again.
>> >> 
>> >> The moment you register that instance callbacks can start coming.
>> >> Leon move the register call last for a good reason - all drivers
>> >> we looked at had bugs in handling init.
>> >
>> >Plus we had very cozy lock->unlock->lock sequences during devlink
>> >command execution, which caused to races between devlink calls
>> >and driver initialization.
>> 
>> So? Why do you think it is a problem?
>
>We need to see the actual implementation. In general, once you unlock
>you can get other threads to change the state of your device.

Sure, I still don't understand, why it would be a problem.

>
>> 
>> >
>> >So I'm also interested to see what Jiri meant by saying "I unlock for
>> >register and for the rest of the init I lock again".
>> >
>> >Thanks