linux-kernel - Re: [PATCH] pcmcia: synclink_cs: Fix use-after-free in mgslpc

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Message-ID: <YyLcG1hG5d6D4zNN@owl.dominikbrodowski.net>
Date:   Thu, 15 Sep 2022 10:02:35 +0200
From:   Dominik Brodowski <linux@...inikbrodowski.net>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     Hyunwoo Kim <imv4bel@...il.com>, laforge@...monks.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>,
        linux-kernel@...r.kernel.org, Paul Fulghum <paulkf@...rogate.com>,
        akpm@...l.org, Lubomir Rintel <lkundrak@...sk>
Subject: Re: [PATCH] pcmcia: synclink_cs: Fix use-after-free in mgslpc_ioctl()

Am Thu, Sep 15, 2022 at 09:35:51AM +0200 schrieb Arnd Bergmann:
> On Thu, Sep 15, 2022, at 4:08 AM, Hyunwoo Kim wrote:
> > There are 3 other pcmica drivers in the path 
> > "drivers/char/pcmcia/synclink_cs.c", 
> > the path of the "synclink_cs.c" driver I reported the UAF to.
> > A similar UAF occurs in the "cm4000_cs.c" and "cm4040_cs.c" drivers. 
> > (this does not happen in scr24x_cs.c)
> ...
> > In the cm4000_cs.c driver, the race condition flow is tricky because of 
> > the start/stop_monitor() functions.
> >
> > The overall flow is similar to cm4040_cs.c.
> > Added one race condition to bypass the "dev->monitor_running" check.
> >
> >
> > So, should the above two drivers be removed from the kernel like the 
> > synclink_cs.c driver?
> >
> > Or should I submit a patch that fixes the UAF?
> 
> There is a good chance that we can remove both now, along with the
> synclink_cs. The scr24x driver is from 2016, but of course the
> hardware is much older. The cm4040/cm4000 drivers are from 2005.
> My guess is that the hardware still exists in actively used systems,
> but none of them get upgraded to modern kernels any more.
> 
> Let's just ask the driver authors (Lubomir and Harald) if they
> think the drivers may still be needed.

Actually, I'd prefer to apply a patch to fix this now-known problem first,
even if we deactive / remove these drivers immediately afterwards.

Thanks,
	Dominik