Revert "android: binder: fix dangling pointer comparison"

This reverts commit 7b142d8fd0.

It doesn't seem to be correct, no one seems to have tested it, and the
email address of the submitter now bounces :(

So revert it.

Cc: Jann Horn <jannh@google.com>
Cc: Chen Feng <puck.chen@hisilicon.com>
Cc: stable <stable@vger.kernel.org>
Cc: Arve Hjønnevåg <arve@android.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/android/binder.c

@@ -2962,7 +2962,6 @@ static int binder_open(struct inode *nodp, struct file *filp)
 		return -ENOMEM;
 	get_task_struct(current);
 	proc->tsk = current;
-	atomic_inc(&current->mm->mm_count);
 	proc->vma_vm_mm = current->mm;
 	INIT_LIST_HEAD(&proc->todo);
 	init_waitqueue_head(&proc->wait);
@@ -3168,7 +3167,6 @@ static void binder_deferred_release(struct binder_proc *proc)
 		vfree(proc->buffer);
 	}
 
-	mmdrop(proc->vma_vm_mm);
 	put_task_struct(proc->tsk);
 
 	binder_debug(BINDER_DEBUG_OPEN_CLOSE,