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: stable@vger.kernel.org Suggested-by: Alice Ryhl aliceryhl@google.com Link: https://lore.kernel.org/all/CAH5fLghapZJ4PbbkC8V5A6Zay-_sgTzwVpwqk6RWWUNKKyJ... [1] Signed-off-by: Carlos Llamas cmllamas@google.com --- drivers/android/binder.c | 28 +++++++++++++--------------- 1 file 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);