netdev - Re: [PATCH net 000/117] net: avoid to remove module when its debugfs is being used

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Date:   Fri, 9 Oct 2020 19:07:16 +0900
From:   Taehee Yoo <ap420073@...il.com>
To:     Nicolai Stange <nstange@...e.de>
Cc:     Johannes Berg <johannes@...solutions.net>,
        David Laight <David.Laight@...lab.com>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "kuba@...nel.org" <kuba@...nel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-wireless@...r.kernel.org" <linux-wireless@...r.kernel.org>,
        "wil6210@....qualcomm.com" <wil6210@....qualcomm.com>,
        "b43-dev@...ts.infradead.org" <b43-dev@...ts.infradead.org>,
        "linux-bluetooth@...r.kernel.org" <linux-bluetooth@...r.kernel.org>
Subject: Re: [PATCH net 000/117] net: avoid to remove module when its debugfs
 is being used

On Fri, 9 Oct 2020 at 14:39, Nicolai Stange <nstange@...e.de> wrote:
>

Hi Nicolai,
Thank you for the review!

> Taehee Yoo <ap420073@...il.com> writes:
>
> > On Fri, 9 Oct 2020 at 01:14, Johannes Berg <johannes@...solutions.net> wrote:
> > On Thu, 2020-10-08 at 15:59 +0000, David Laight wrote:
> >
> >> From: Taehee Yoo
> >> > Sent: 08 October 2020 16:49
> >> >
> >> > When debugfs file is opened, its module should not be removed until
> >> > it's closed.
> >> > Because debugfs internally uses the module's data.
> >> > So, it could access freed memory.
>
> Yes, the file_operations' ->release() to be more specific -- that's not
> covered by debugfs' proxy fops.
>
>
> >> > In order to avoid panic, it just sets .owner to THIS_MODULE.
> >> > So that all modules will be held when its debugfs file is opened.
> >>
> >> Can't you fix it in common code?
> >
> >> Yeah I was just wondering that too - weren't the proxy_fops even already
> >> intended to fix this?
> >
> > I didn't try to fix this issue in the common code(debugfs).
> > Because I thought It's a typical pattern of panic and THIS_MODULE
> > can fix it clearly.
> > So I couldn't think there is a root reason in the common code.
>
> That's correct, ->owner should get set properly, c.f. my other mail in
> this thread.
>

Thanks a lot for verifying it!
Taehee