On 11/15/23 5:09 AM, Yoshihiro Shimoda wrote:
[...]
>>> Fix races between ravb_tx_timeout_work() and functions of net_device_ops
>>> and ethtool_ops by using rtnl_trylock() and rtnl_unlock(). Note that
>>> since ravb_close() is under the rtnl lock and calls cancel_work_sync(),
>>> ravb_tx_timeout_work() should calls rtnl_trylock(). Otherwise, a deadlock
>>> may happen in ravb_tx_timeout_work() like below:
>>>
>>> CPU0 CPU1
>>> ravb_tx_timeout()
>>> schedule_work()
>>> ...
>>> __dev_close_many()
>>> // Under rtnl lock
>>> ravb_close()
>>> cancel_work_sync()
>>> // Waiting
>>> ravb_tx_timeout_work()
>>> rtnl_lock()
>>> // This is possible to cause a deadlock
>>>
>>> Fixes: c156633f1353 ("Renesas Ethernet AVB driver proper")
>>> Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@xxxxxxxxxxx>
>>
>> Reviewed-by: Sergey Shtylyov <s.shtylyov@xxxxxx>
[...]
>>> diff --git a/drivers/net/ethernet/renesas/ravb_main.c b/drivers/net/ethernet/renesas/ravb_main.c
>>> index 0ef0b88b7145..300c1885e1e1 100644
>>> --- a/drivers/net/ethernet/renesas/ravb_main.c
>>> +++ b/drivers/net/ethernet/renesas/ravb_main.c
>>> @@ -1874,6 +1874,9 @@ static void ravb_tx_timeout_work(struct work_struct *work)
>>> struct net_device *ndev = priv->ndev;
>>> int error;
>>>
>>> + if (!rtnl_trylock())
>>> + return;
>>
>> I wonder if we should reschedule the work here...
>
> I think so. But, it should reschedule the work if the netif is still running because
> Use-after-free issue happens again when cancel_work_sync() is calling. Also, I also think
> we should use schedule_delayed_work() instead. So, I'll submit such a patch as v3.
I'm not really sure about that one. Note that cancel_work_sync() should
work with the works requeueing themselves, the comments say...
> Best regards,
> Yoshihiro Shimoda
[...]
MBR, Sergey
