linux-kernel - Re: [PATCH] binder: fix possible UAF when freeing buffer

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Date:   Thu, 13 Jun 2019 08:43:59 -0700
From:   Todd Kjos <tkjos@...gle.com>
To:     Greg KH <gregkh@...uxfoundation.org>
Cc:     Todd Kjos <tkjos@...roid.com>,
        Arve Hjønnevåg <arve@...roid.com>,
        "open list:ANDROID DRIVERS" <devel@...verdev.osuosl.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Martijn Coenen <maco@...gle.com>,
        "Joel Fernandes (Google)" <joel@...lfernandes.org>,
        Android Kernel Team <kernel-team@...roid.com>
Subject: Re: [PATCH] binder: fix possible UAF when freeing buffer

On Wed, Jun 12, 2019 at 10:41 PM Greg KH <gregkh@...uxfoundation.org> wrote:
>
> On Wed, Jun 12, 2019 at 01:29:27PM -0700, Todd Kjos wrote:
> > There is a race between the binder driver cleaning
> > up a completed transaction via binder_free_transaction()
> > and a user calling binder_ioctl(BC_FREE_BUFFER) to
> > release a buffer. It doesn't matter which is first but
> > they need to be protected against running concurrently
> > which can result in a UAF.
> >
> > Signed-off-by: Todd Kjos <tkjos@...gle.com>
> > ---
> >  drivers/android/binder.c | 16 ++++++++++++++--
> >  1 file changed, 14 insertions(+), 2 deletions(-)
>
> Does this also need to go to the stable kernels?

This patch won't apply cleanly to stable kernels so I'll submit a new
patch directly to stable@ (4.14, 4.19) once this one lands.

>
> thanks,
>
> greg k-h