From 33b6a1f155d627f5bd80c7485c598ce45428f74f Mon Sep 17 00:00:00 2001 From: "Uladzislau Rezki (Sony)" Date: Tue, 10 Jun 2025 19:34:48 +0200 Subject: [PATCH] rcu: Return early if callback is not specified Currently the call_rcu() API does not check whether a callback pointer is NULL. If NULL is passed, rcu_core() will try to invoke it, resulting in NULL pointer dereference and a kernel crash. To prevent this and improve debuggability, this patch adds a check for NULL and emits a kernel stack trace to help identify a faulty caller. Signed-off-by: Uladzislau Rezki (Sony) Reviewed-by: Joel Fernandes Signed-off-by: Joel Fernandes --- kernel/rcu/tree.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index e8a4b720d7d2..14d4499c6fc3 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -3072,6 +3072,10 @@ __call_rcu_common(struct rcu_head *head, rcu_callback_t func, bool lazy_in) /* Misaligned rcu_head! */ WARN_ON_ONCE((unsigned long)head & (sizeof(void *) - 1)); + /* Avoid NULL dereference if callback is NULL. */ + if (WARN_ON_ONCE(!func)) + return; + if (debug_rcu_head_queue(head)) { /* * Probable double call_rcu(), so leak the callback. -- 2.25.1