From: Todd Kjos <tkjos@google.com>
To: Greg KH <gregkh@linuxfoundation.org>
Cc: "Todd Kjos" <tkjos@android.com>,
"Arve Hjønnevåg" <arve@android.com>,
"open list:ANDROID DRIVERS" <devel@driverdev.osuosl.org>,
LKML <linux-kernel@vger.kernel.org>,
"Martijn Coenen" <maco@google.com>,
"Joel Fernandes (Google)" <joel@joelfernandes.org>,
"Android Kernel Team" <kernel-team@android.com>
Subject: Re: [PATCH] binder: fix race between munmap() and direct reclaim
Date: Sat, 2 Mar 2019 08:27:44 -0800 [thread overview]
Message-ID: <CAHRSSExy=kWt+MDzD10VogfasygJET6FmEtRc9vJuLv4Ov7+uA@mail.gmail.com> (raw)
In-Reply-To: <20190302075720.GA18046@kroah.com>
On Fri, Mar 1, 2019 at 11:57 PM Greg KH <gregkh@linuxfoundation.org> wrote:
>
> On Fri, Mar 01, 2019 at 03:06:06PM -0800, Todd Kjos wrote:
> > An munmap() on a binder device causes binder_vma_close() to be called
> > which clears the alloc->vma pointer.
> >
> > If direct reclaim causes binder_alloc_free_page() to be called, there
> > is a race where alloc->vma is read into a local vma pointer and then
> > used later after the mm->mmap_sem is acquired. This can result in
> > calling zap_page_range() with an invalid vma which manifests as a
> > use-after-free in zap_page_range().
> >
> > The fix is to check alloc->vma after acquiring the mmap_sem (which we
> > were acquiring anyway) and skip zap_page_range() if it has changed
> > to NULL.
> >
> > Signed-off-by: Todd Kjos <tkjos@google.com>
> > ---
>
> Any specific commit that this fixes?
No, it's been there a long time.
> And should it be marked for stable releases?
It is needed in stable (back to 4.4), but will need to be backported.
Should I post backported versions targeting the specific releases now?
I was thinking we'd wait for this one to land. I think we'll need 1
patch for 4.4/4.9 and a second one for 4.14/4.19 (and some of those
backported patches will have conflicts when merged down to android-4.X
-- I think the 4.14/4.19 version will apply to all the android
branches). Let me know how you want to handle this.
>
> thanks,
>
> greg k-h
next prev parent reply other threads:[~2019-03-02 16:28 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-01 23:06 [PATCH] binder: fix race between munmap() and direct reclaim Todd Kjos
2019-03-02 7:57 ` Greg KH
2019-03-02 16:27 ` Todd Kjos [this message]
2019-03-05 19:35 ` Joel Fernandes
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