netdev - Re: [PATCH net-next v1 2/2] netpoll: avoid reference leaks

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Message-ID: <CAG88wWa9WTz4gwLHWAys1e96eWBgD+mcVW=hPh7a+b2ooJzBeQ@mail.gmail.com>
Date:	Tue, 8 Jul 2014 14:50:24 -0700
From:	David Decotigny <decot@...glers.com>
To:	David Miller <davem@...emloft.net>
Cc:	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Eric Dumazet <edumazet@...gle.com>, amwang@...hat.com,
	antonio@...hcoding.com, Jiri Pirko <jpirko@...hat.com>
Subject: Re: [PATCH net-next v1 2/2] netpoll: avoid reference leaks

In that case, that's what the original code does: dropping this patch 2/2.

Patch 1/2 "netpoll: fix use after free" is still needed to prevent
panics, though.

On Tue, Jul 8, 2014 at 2:17 PM, David Miller <davem@...emloft.net> wrote:
> From: David Decotigny <decot@...glers.com>
> Date: Tue, 8 Jul 2014 12:35:14 -0700
>
>> Thanks for the feedback. This patch results from manual inspection of
>> the code. I agree my commit description is abusive: in the case of
>> bonding, I think everything is fine, there should be no ref leak,
>> cleanup paths seem clean.
>>
>> My point was to make things more predictable: ndo_netpoll_cleanup
>> called anyways to acknowledge actual loss of a ref to npinfo,
>> irrespective of whether it's the last ref or not. Without this patch,
>> calling ndo_netpoll_cleanup would depend on some timing behavior, hard
>> to predict, and users of the API have better be careful to reclaim the
>> refs manually anyways: as a consequence, not sure this callback is
>> actually required in its current inception.
>
> You've increased my confusion rather than decreased it.
>
> You fail to address the core issue in my feedback:
>
>         Whoever drops the refcount to zero must be the one to invoke
>         the cleanup function.
>
> Please address this concisely, and directly.
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