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

From: Greg KH
Date: Sat Mar 02 2019 - 03:00:23 EST

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@xxxxxxxxxx>
> ---

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


greg k-h