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

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Message-ID: <CA+55aFxuha1tQXcn+WtbOKzwwmtA8AORb04tMM=hk6jT3ntt3w@mail.gmail.com>
Date:   Thu, 6 Sep 2018 22:04:49 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     dingxiang@...s.chinamobile.com
Cc:     martyn@...chs.me.uk, 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, 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.

Greg?

              Linus