Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Subject: Re: [PATCH] veth: fix memory leak in veth_newlink()
To:     Rustam Kovhaev <rkovhaev@gmail.com>
Cc:     davem@davemloft.net, kuba@kernel.org, netdev@vger.kernel.org,
        bpf@vger.kernel.org, linux-kernel@vger.kernel.org,
        gregkh@linuxfoundation.org
References: <20200830131336.275844-1-rkovhaev@gmail.com>
 <32e30526-bcc9-1f2f-1250-f36687561fbb@gmail.com>
 <20200831005133.GA3295@thinkpad>
From:   Toshiaki Makita <toshiaki.makita1@gmail.com>
Message-ID: <01c8fa29-8bda-ccae-b7fb-8df85992b437@gmail.com>
Date:   Mon, 31 Aug 2020 10:43:57 +0900
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101
 Thunderbird/68.3.1
MIME-Version: 1.0
In-Reply-To: <20200831005133.GA3295@thinkpad>
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Language: en-US
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On 2020/08/31 9:51, Rustam Kovhaev wrote:
> On Mon, Aug 31, 2020 at 09:16:32AM +0900, Toshiaki Makita wrote:
>> On 2020/08/30 22:13, Rustam Kovhaev wrote:
>>> when register_netdevice(dev) fails we should check whether struct
>>> veth_rq has been allocated via ndo_init callback and free it, because,
>>> depending on the code path, register_netdevice() might not call
>>> priv_destructor() callback
>>
>> AFAICS, register_netdevice() always goto err_uninit and calls priv_destructor()
>> on failure after ndo_init() succeeded.
>> So I could not find such a code path.
>> Would you elaborate on it?
> 
> in net/core/dev.c:9863, where register_netdevice() calls rollback_registered(),
> which does not call priv_destructor(), then register_netdevice() returns error
> net/core/dev.c:9884

Thank you, now I see the code path.
But then all devices which allocate something in ndo_init() and free them in
priv_destructor() are affected? E.g. loopback and ifb seem to do such thing.
Why not calling priv_destructor() after invocation of rollback_registered()?
It looks weird that only that path does not call priv_destructor().

Toshiaki Makita