netdev - Re: [PATCH net v2 00/21] net: avoid to remove module when its debugfs is being used

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Date:   Tue, 10 Nov 2020 09:32:49 +0100
From:   Johannes Berg <johannes@...solutions.net>
To:     Jakub Kicinski <kuba@...nel.org>, Taehee Yoo <ap420073@...il.com>
Cc:     davem@...emloft.net, netdev@...r.kernel.org,
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Subject: Re: [PATCH net v2 00/21] net: avoid to remove module when its
 debugfs is being used

On Sat, 2020-11-07 at 11:05 -0800, Jakub Kicinski wrote:
> On Sat,  7 Nov 2020 17:21:31 +0000 Taehee Yoo wrote:
> > 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.
> > 
> > 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.
> 
> Hm, looks like some of the patches need to be revised because
> .owner is already set in the ops, and a warning gets generated.
> 
> Also it'd be good to mention why Johannes's approach was abandoned.

Well, I had two.

One was awful, and worked in all cases.

The other was less awful, and didn't work in all cases.

I think both gave Al Viro hives ;-)

> Patch 1 needs to be split in two. Patches 2 and 3 would go via Johannes.

FWIW, I'm happy for you to take patches 2 and 3 as well, but I guess if
patch 1 needs to be split there's a resend coming anyway, so then I'll
be happy to take the patches 2/3 from a separate set.

johannes