netdev - RE: [PATCH net v3] driver: veth: Fix one possbile memleak when fail to register

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Message-ID: <006101d2c3d7$bf814230$3e83c690$@foxmail.com>
Date:   Wed, 3 May 2017 14:37:33 +0800
From:   "Gao Feng" <gfree.wind@...mail.com>
To:     "'Xin Long'" <lucien.xin@...il.com>
Cc:     "'Gao Feng'" <gfree.wind@....163.com>,
        "'davem'" <davem@...emloft.net>, <jarod@...hat.com>,
        "'Stephen Hemminger'" <stephen@...workplumber.org>,
        <dsa@...ulusnetworks.com>, "'network dev'" <netdev@...r.kernel.org>
Subject: RE: [PATCH net v3] driver: veth: Fix one possbile memleak when fail to register_netdevice

> From: Xin Long [mailto:lucien.xin@...il.com]
> Sent: Wednesday, May 3, 2017 1:38 PM
> On Wed, May 3, 2017 at 10:07 AM, Gao Feng <gfree.wind@...mail.com>
> wrote:
> >> From: netdev-owner@...r.kernel.org
> >> [mailto:netdev-owner@...r.kernel.org]
> >> On Behalf Of Xin Long
> >> Sent: Wednesday, May 3, 2017 12:59 AM On Tue, May 2, 2017 at 7:03 PM,
> >> Gao Feng <gfree.wind@....163.com> wrote:
> >> >> From: Xin Long [mailto:lucien.xin@...il.com]
> >> >> Sent: Tuesday, May 2, 2017 3:56 PM On Sat, Apr 29, 2017 at 11:51
> >> >> AM,  <gfree.wind@...mail.com> wrote:
> >> >> > From: Gao Feng <gfree.wind@...mail.com>
[...]
> > The fix you mentioned change the original logic.
> > The dev->vstats is freed in advance in the ndo_uninit, not destructor.
> > It may break the backward.
> Sorry, I didn't get your "backward"
> I can't see there will be any problem caused by it.
> can you say this patch also break the 'backward' ?
> https://patchwork.ozlabs.org/patch/748964/
> 
> It's really weird to do dev->reg_state check in ndo_unint ndo_unint is supposed
> to free the memory alloced in ndo_init.
> 

I am not sure if it would break the backward, so I said it MAY break.
I assumed there may be someone would access the dev->vstats after ndo_uninit,
because current veth driver free the mem in the destructor.
I selected this approach because I don't want to bring new bugs during fix bug.

If you're sure it is safe to free dev->vstats in ndo_uninit, I would like to update it.

BTW there are too many drivers which have possible memleak.
You could find the list by https://www.mail-archive.com/netdev@vger.kernel.org/msg166629.html.

Some drivers allocate the resources in ndo_init, free some in ndo_uninit and free left in destructor.
I think there are some reasons. 
We could not move all free in the ndo_uninit from destructor. What's your opinion?

Best Regards
Feng