netdev - Re: [PATCH v2 2/2] net: io_uring/zcrx: call netdev_queue_get_dma

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Message-ID: <839bc664-0e4b-4e70-9a9e-6f0c4c896d9e@davidwei.uk>
Date: Wed, 29 Oct 2025 18:09:41 -0700
From: David Wei <dw@...idwei.uk>
To: Jakub Kicinski <kuba@...nel.org>
Cc: io-uring@...r.kernel.org, netdev@...r.kernel.org,
 Jens Axboe <axboe@...nel.dk>, Pavel Begunkov <asml.silence@...il.com>,
 "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
 Paolo Abeni <pabeni@...hat.com>, Simon Horman <horms@...nel.org>
Subject: Re: [PATCH v2 2/2] net: io_uring/zcrx: call
 netdev_queue_get_dma_dev() under instance lock

On 2025-10-29 16:54, Jakub Kicinski wrote:
> On Wed, 29 Oct 2025 16:16:54 -0700 David Wei wrote:
>> +	ifq->netdev = netdev_get_by_index_lock(current->nsproxy->net_ns, reg.if_idx);
>>   	if (!ifq->netdev) {
>>   		ret = -ENODEV;
>> -		goto err;
>> +		goto netdev_unlock;
>>   	}
>>   
>>   	ifq->dev = netdev_queue_get_dma_dev(ifq->netdev, reg.if_rxq);
>>   	if (!ifq->dev) {
>>   		ret = -EOPNOTSUPP;
>> -		goto err;
>> +		goto netdev_unlock;
>>   	}
>> +	netdev_hold(ifq->netdev, &ifq->netdev_tracker, GFP_KERNEL);
>>   	get_device(ifq->dev);
>>   
>>   	ret = io_zcrx_create_area(ifq, &area);
>>   	if (ret)
>> -		goto err;
>> +		goto netdev_unlock;
> 
> Without looking at larger context this looks sus.
> You're jumping to the same label before and after you took the ref on
> the netdev..

Sorry you're right, and actually io_zcrx_ifq_free() does netdev_put()
unconditionally. I'll correct this in v3.