binder: allow freeze notification for dead nodes

Alice points out that binder_request_freeze_notification() should not
return EINVAL when the relevant node is dead [1]. The node can die at
any point even if the user input is valid. Instead, allow the request
to be allocated but skip the initial notification for dead nodes. This
avoids propagating unnecessary errors back to userspace.

Fixes: d579b04a52a1 ("binder: frozen notification")
Cc: [email protected]
Suggested-by: Alice Ryhl <[email protected]>
Link: https://lore.kernel.org/all/CAH5fLghapZJ4PbbkC8V5A6Zay-_sgTzwVpwqk6RWWUNKKyJC_Q@mail.gmail.com/ [1]
Signed-off-by: Carlos Llamas <[email protected]>
Acked-by: Todd Kjos <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>

1 files changed, 13 insertions, 15 deletions

diff --git a/drivers/android/binder.c b/drivers/android/binder.c
index 73dc6cbc1681..415fc9759249 100644
--- a/drivers/android/binder.c
+++ b/drivers/android/binder.c
@@ -3856,7 +3856,6 @@ binder_request_freeze_notification(struct binder_proc *proc,
 {
 	struct binder_ref_freeze *freeze;
 	struct binder_ref *ref;
-	bool is_frozen;
 
 	freeze = kzalloc(sizeof(*freeze), GFP_KERNEL);
 	if (!freeze)
@@ -3872,32 +3871,31 @@ binder_request_freeze_notification(struct binder_proc *proc,
 	}
 
 	binder_node_lock(ref->node);
-
-	if (ref->freeze || !ref->node->proc) {
-		binder_user_error("%d:%d invalid BC_REQUEST_FREEZE_NOTIFICATION %s\n",
-				  proc->pid, thread->pid,
-				  ref->freeze ? "already set" : "dead node");
+	if (ref->freeze) {
+		binder_user_error("%d:%d BC_REQUEST_FREEZE_NOTIFICATION already set\n",
+				  proc->pid, thread->pid);
 		binder_node_unlock(ref->node);
 		binder_proc_unlock(proc);
 		kfree(freeze);
 		return -EINVAL;
 	}
-	binder_inner_proc_lock(ref->node->proc);
-	is_frozen = ref->node->proc->is_frozen;
-	binder_inner_proc_unlock(ref->node->proc);
 
 	binder_stats_created(BINDER_STAT_FREEZE);
 	INIT_LIST_HEAD(&freeze->work.entry);
 	freeze->cookie = handle_cookie->cookie;
 	freeze->work.type = BINDER_WORK_FROZEN_BINDER;
-	freeze->is_frozen = is_frozen;
-
 	ref->freeze = freeze;
 
-	binder_inner_proc_lock(proc);
-	binder_enqueue_work_ilocked(&ref->freeze->work, &proc->todo);
-	binder_wakeup_proc_ilocked(proc);
-	binder_inner_proc_unlock(proc);
+	if (ref->node->proc) {
+		binder_inner_proc_lock(ref->node->proc);
+		freeze->is_frozen = ref->node->proc->is_frozen;
+		binder_inner_proc_unlock(ref->node->proc);
+
+		binder_inner_proc_lock(proc);
+		binder_enqueue_work_ilocked(&freeze->work, &proc->todo);
+		binder_wakeup_proc_ilocked(proc);
+		binder_inner_proc_unlock(proc);
+	}
 
 	binder_node_unlock(ref->node);
 	binder_proc_unlock(proc);