Revert "binder: Prevent context manager from incrementing ref 0"

This reverts commit c5665cafbedd2e2a523fe933e452391a02d3adb3.

This patch was causing display hangs for Qualcomm after the 5.4.58
merge.

Bug: 166779391
Change-Id: Iaf22ede68247422709b00f059e5c4d517f219adf
Signed-off-by: Todd Kjos <tkjos@google.com>

# Conflicts:
#	drivers/android/binder.c

drivers/android/binder.c

@@ -3157,14 +3157,8 @@ static void binder_transaction(struct binder_proc *proc,
 			goto err_dead_binder;
 		}
 		e->to_node = target_node->debug_id;
-		if (WARN_ON(proc == target_proc)) {
-			return_error = BR_FAILED_REPLY;
-			return_error_param = -EINVAL;
-			return_error_line = __LINE__;
-			goto err_invalid_target_handle;
-		}
-		if (security_binder_transaction(proc->cred,
-						target_proc->cred) < 0) {
+		if (security_binder_transaction(proc->tsk,
+						target_proc->tsk) < 0) {
 			return_error = BR_FAILED_REPLY;
 			return_error_param = -EPERM;
 			return_error_line = __LINE__;
@@ -3774,17 +3768,10 @@ static int binder_thread_write(struct binder_proc *proc,
 				struct binder_node *ctx_mgr_node;
 				mutex_lock(&context->context_mgr_node_lock);
 				ctx_mgr_node = context->binder_context_mgr_node;
-				if (ctx_mgr_node) {
-					if (ctx_mgr_node->proc == proc) {
-						binder_user_error("%d:%d context manager tried to acquire desc 0\n",
-								  proc->pid, thread->pid);
-						mutex_unlock(&context->context_mgr_node_lock);
-						return -EINVAL;
-					}
+				if (ctx_mgr_node)
 					ret = binder_inc_ref_for_node(
 							proc, ctx_mgr_node,
 							strong, NULL, &rdata);
-				}
 				mutex_unlock(&context->context_mgr_node_lock);
 			}
 			if (ret)