netdev - Re: [PATCH net-next 0/2] Bonding: support new xfrm state offload functions

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Message-ID: <bbb2c180-d38d-4bda-bc24-9500eb97cd65@blackwall.org>
Date: Fri, 16 Aug 2024 12:04:18 +0300
From: Nikolay Aleksandrov <razor@...ckwall.org>
To: Hangbin Liu <liuhangbin@...il.com>
Cc: netdev@...r.kernel.org, Jay Vosburgh <j.vosburgh@...il.com>,
 "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>,
 Paolo Abeni <pabeni@...hat.com>, Eric Dumazet <edumazet@...gle.com>,
 Tariq Toukan <tariqt@...dia.com>, Jianbo Liu <jianbol@...dia.com>,
 Sabrina Dubroca <sd@...asysnail.net>
Subject: Re: [PATCH net-next 0/2] Bonding: support new xfrm state offload
 functions

On 16/08/2024 11:37, Nikolay Aleksandrov wrote:
> On 16/08/2024 11:32, Hangbin Liu wrote:
>> On Fri, Aug 16, 2024 at 09:06:12AM +0300, Nikolay Aleksandrov wrote:
>>> On 16/08/2024 06:55, Hangbin Liu wrote:
>>>> I planned to add the new XFRM state offload functions after Jianbo's
>>>> patchset [1], but it seems that may take some time. Therefore, I am
>>>> posting these two patches to net-next now, as our users are waiting for
>>>> this functionality. If Jianbo's patch is applied first, I can update these
>>>> patches accordingly.
>>>>
>>>> [1] https://lore.kernel.org/netdev/20240815142103.2253886-2-tariqt@nvidia.com
>>>>
>>>> Hangbin Liu (2):
>>>>   bonding: Add ESN support to IPSec HW offload
>>>>   bonding: support xfrm state update
>>>>
>>>>  drivers/net/bonding/bond_main.c | 76 +++++++++++++++++++++++++++++++++
>>>>  1 file changed, 76 insertions(+)
>>>>
>>>
>>> (not related to this set, but to bond xfrm)
>>> By the way looking at bond's xfrm code, what prevents bond_ipsec_offload_ok()
>>> from dereferencing a null ptr?
>>> I mean it does:
>>>         curr_active = rcu_dereference(bond->curr_active_slave);
>>>         real_dev = curr_active->dev;
>>>
>>> If this is running only under RCU as the code suggests then
>>> curr_active_slave can change to NULL in parallel. Should there be a
>>> check for curr_active before deref or am I missing something?
>>
>> Yes, we can do like
>> real_dev = curr_active ? curr_active->dev : NULL;
>>
>> Thanks
>> Hangbin
> 
> Right, let me try and trigger it and I'll send a patch. :)
> 

Just fyi I was able to trigger this null deref easily and one more
thing - there is a second null deref after this one because real_dev is
used directly :(

I'll send a patch to fix both in a bit.