Re: [PATCH v3 0/4] Fix multiple race condition vulnerabilities in dvb-core and device driver

[Hyunwoo Kim <v4bel@theori.io>]

On Tue, Mar 07, 2023 at 09:57:13PM +0900, Hyunwoo Kim wrote:
> ttusb_dec is a comment for patch #4 in the series.
> And as102 is the #1 patch.
> 
> 
> Regards,
> Hyunwoo Kim

I was using the wrong email client and the mailing list didn't get sent, sorry.

Resend the mail for the mailing list.

> 
> 
> 2023년 3월 7일 (화) 오후 9:41, Mauro Carvalho Chehab <mchehab@kernel.org>님이 작성:
> 
> > Em Wed, 16 Nov 2022 20:59:21 -0800
> > Hyunwoo Kim <imv4bel@gmail.com> escreveu:
> >
> > > Dear,
> > >
> > > This patch set is a security patch for various race condition
> > vulnerabilities that occur
> > > in 'dvb-core' and 'ttusb_dec', a dvb-based device driver.
> > >
> > >
> > > # 1. media: dvb-core: Fix use-after-free due to race condition occurring
> > in dvb_frontend
> > > This is a security patch for a race condition that occurs in the
> > dvb_frontend system of dvb-core.
> > >
> > > The race condition that occurs here will occur with _any_ device driver
> > using dvb_frontend.
> > >
> > > The race conditions that occur in dvb_frontend are as follows
> > > (Description is based on drivers/media/usb/as102/as102_drv.c using
> > dvb_frontend):
> > > ```
> > >                 cpu0                                                cpu1
> > >        1. open()
> > >           dvb_frontend_open()
> > >           dvb_frontend_get()    // kref : 3
> > >
> > >
> > >                                                              2.
> > as102_usb_disconnect()
> > >
> >  as102_dvb_unregister()
> > >
> >  dvb_unregister_frontend()
> > >
> >  dvb_frontend_put()    // kref : 2
> > >
> >  dvb_frontend_detach()
> > >
> >  dvb_frontend_put()    // kref : 1
> > >        3. close()
> > >           __fput()
> > >           dvb_frontend_release()
> > >           dvb_frontend_put()    // kref : 0
> > >           dvb_frontend_free()
> > >           __dvb_frontend_free()
> > >           dvb_free_device()
> > >           kfree (dvbdev->fops);
> > >           ...
> > >           fops_put(file->f_op);    // UAF!!
> >
> > Hmm... you're mentioning ttusb_dec at the comment, but here you're showing
> > the race for as102, which is a different driver.
> >
> > I'm confused.
> >
> >
> > Thanks,
> > Mauro
> >