On Wed, Jun 11, 2025 at 11:02:03AM -0700, syzbot wrote:
> Hello,
>
> syzbot tried to test the proposed patch but the build/boot failed:
>
> failed to apply patch:
> checking file kernel/rcu/tree.c
> patch: **** unexpected end of file in patch
>
>
>
> Tested on:
>
> commit: aef17cb3 Revert "mm/damon/Kconfig: enable CONFIG_DAMON..
> git tree: upstream
> kernel config: https://syzkaller.appspot.com/x/.config?x=523d3ff8e053340a
> dashboard link: https://syzkaller.appspot.com/bug?extid=80e5d6f453f14a53383a
> compiler:
> patch: https://syzkaller.appspot.com/x/patch.diff?x=17de99d4580000
>
#syz test
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.
