netdev - Re: [RFC] about net: Fix inconsistent teardown and release of private netdev state.

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Message-Id: <20170818.155835.2053259542629638150.davem@davemloft.net>
Date:   Fri, 18 Aug 2017 15:58:35 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     eric.dumazet@...il.com
Cc:     netdev@...r.kernel.org
Subject: Re: [RFC] about net: Fix inconsistent teardown and release of
 private netdev state.

From: Eric Dumazet <eric.dumazet@...il.com>
Date: Fri, 18 Aug 2017 06:13:49 -0700

> On Thu, 2017-08-17 at 22:21 -0700, David Miller wrote:
>> From: Eric Dumazet <eric.dumazet@...il.com>
>> Date: Thu, 17 Aug 2017 15:30:40 -0700
>> 
>> > So we do not really know if we need to clean up or not.
>> 
>> We always know, the answer is that whenever register_netdev() fails we
>> never need to perform any cleanup which is done by priv_destructor.
>> 
>> > Any idea how to fix the issue ?
>> 
>> Your patch is exactly how we should fix this, but without the comment.
>> The logic is straightforward.
>> 
>> If register_netdevice() fails any resources handled by priv_destructor
>> are cleaned up, it is guaranteed.
> 
> Not in current code.
> 
> There are some failures which do a "goto out;" 
> 
> out:
> 	return ret;
> 
> 
> In these cases, priv_destructor is not called.
> 
> So we need multiple fixes I think :/

I don't think so.

The cases that "goto out;" in register_netdevce() are those that
execute before ->ndo_init() succeeds.

Only if ->ndo_succeeds() runs successfully should ->priv_destructor()
need execute.

So everything is fine as far as I can see.