linux-kernel - Re: [PATCH] vme: remove unneeded kfree

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Date:   Fri, 07 Sep 2018 09:33:08 +0100
From:   Martyn Welch <martyn@...chs.me.uk>
To:     Linus Torvalds <torvalds@...ux-foundation.org>,
        dingxiang@...s.chinamobile.com
Cc:     manohar.vanga@...il.com,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Staging subsystem List <devel@...verdev.osuosl.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] vme: remove unneeded kfree

On Thu, 2018-09-06 at 22:04 -0700, Linus Torvalds wrote:
> On Thu, Sep 6, 2018 at 1:51 AM Ding Xiang
> <dingxiang@...s.chinamobile.com> wrote:
> > 
> > put_device will call vme_dev_release to free vdev, kfree is
> > unnecessary here.
> 
> That does seem to be the case.  I think "unnecessary" is overly kind,
> it does seem to be a double free.
> 
> Looks like the issue was introduced back in 2013 by commit
> def1820d25fa ("vme: add missing put_device() after device_register()
> fails").
> 
> It seems you should *either* kfree() the vdev, _or_ do put_device(),
> but doing both seems wrong.
> 
> I presume the device_register() has never failed, and this being
> vme-only I'm guessing there isn't a vibrant testing community.
> 

I think that is also overly kind :-)

I currently lack access to suitable hardware to test fully myself and I
need to find some time to (re)implement some automated testing, after I
lost access to the bits I had when I left a previous employer. That and
see if I can get access to some hardware again...

Manohar, do you still have access/interest in the VME stuff? You've
been very quiet for a long time now.

Martyn