From: Johannes Berg <johannes@sipsolutions.net>
To: David Laight <David.Laight@ACULAB.COM>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Cc: "nstange@suse.de" <nstange@suse.de>,
"ap420073@gmail.com" <ap420073@gmail.com>,
"netdev@vger.kernel.org" <netdev@vger.kernel.org>,
"linux-wireless@vger.kernel.org" <linux-wireless@vger.kernel.org>,
"gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>,
"rafael@kernel.org" <rafael@kernel.org>
Subject: Re: [RFC] debugfs: protect against rmmod while files are open
Date: Fri, 09 Oct 2020 12:56:59 +0200 [thread overview]
Message-ID: <793a6ba5b534917018165d38bcb5e2c5704d82c7.camel@sipsolutions.net> (raw)
In-Reply-To: <8fe62082d9774a1fb21894c27e140318@AcuMS.aculab.com>
On Fri, 2020-10-09 at 10:56 +0000, David Laight wrote:
> From: Johannes Berg
> > Sent: 09 October 2020 11:48
> >
> > On Fri, 2020-10-09 at 12:41 +0200, Johannes Berg wrote:
> >
> > > If the fops doesn't have a release method, we don't even need
> > > to keep a reference to the real_fops, we can just fops_put()
> > > them already in debugfs remove, and a later full_proxy_release()
> > > won't call anything anyway - this just crashed/UAFed because it
> > > used real_fops, not because there was actually a (now invalid)
> > > release() method.
> >
> > I actually implemented something a bit better than what I described - we
> > never need a reference to the real_fops for the release method alone,
> > and that means if the release method is in the kernel image, rather than
> > a module, it can still be called.
> >
> > That together should reduce the ~117 places you changed in the large
> > patchset to around a handful.
>
> Is there an equivalent problem for normal cdev opens
> in any modules?
I guess so, but since there's no proxy_fops infrastructure and no
revoke(), you can't really do anything else other than adding .owner
properly, afaict.
johannes
next prev parent reply other threads:[~2020-10-09 10:57 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <4a58caee3b6b8975f4ff632bf6d2a6673788157d.camel@sipsolutions.net>
2020-10-09 10:41 ` [RFC] debugfs: protect against rmmod while files are open Johannes Berg
2020-10-09 10:48 ` Johannes Berg
2020-10-09 10:56 ` David Laight
2020-10-09 10:56 ` Johannes Berg [this message]
2020-10-09 11:15 ` gregkh
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