linux-kernel - Re: [PATCH] binder: fix race between munmap() and direct reclaim

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Message-ID: <20190302075720.GA18046@kroah.com>
Date:   Sat, 2 Mar 2019 08:57:20 +0100
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Todd Kjos <tkjos@...roid.com>
Cc:     tkjos@...gle.com, arve@...roid.com, devel@...verdev.osuosl.org,
        linux-kernel@...r.kernel.org, maco@...gle.com,
        joel@...lfernandes.org, kernel-team@...roid.com
Subject: Re: [PATCH] binder: fix race between munmap() and direct reclaim

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@...gle.com>
> ---

Any specific commit that this fixes?  And should it be marked for
stable releases?

thanks,

greg k-h