On Wed, Apr 24, 2019 at 10:35:56AM -0700, Todd Kjos wrote:
From: Todd Kjos tkjos@android.com
commit 5cec2d2e5839f9c0fec319c523a911e0a7fd299f upstream.
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 Reviewed-by: Joel Fernandes (Google) joel@joelfernandes.org Cc: stable stable@vger.kernel.org # 5.0, 4.19, 4.14 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
Greg: This applies to 5.0, 4.19, 4.14. Not needed before 4.12.
Thanks, now queued up.
greg k-h