ANDROID: fix binder change in merge of 4.4.183

The 4.4.183 merge was missing the change to the
binder driver associated with the linux-4.4.y
commit 8f6345a11c ("coredump: fix race condition
between mmget_not_zero()/get_task_mm() and core dumping").
It was left out because the android-4.4 binder driver
has been significantly refactored compared to linux-4.4.y.

This patch applies the missing change from that
patch to the binder driver.

Change-Id: I803e558cb629fedff04b14e23ac9f83e98628ede
Fixes: 94fd42809f ("Merge 4.4.183 into android-4.4")
Signed-off-by: Todd Kjos <tkjos@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>
(cherry picked from commit 6cfb5a870f)

drivers/android/binder_alloc.c

@@ -219,6 +219,11 @@ static int binder_update_page_range(struct binder_alloc *alloc, int allocate,
 
 	if (mm) {
 		down_read(&mm->mmap_sem);
+		if (!mmget_still_valid(mm)) {
+			if (allocate == 0)
+				goto free_range;
+			goto err_no_vma;
+		}
 		vma = alloc->vma;
 	}