[PATCH 5/9] rcu: Validate callback arguments in Tiny RCU

[Kunwu Chan]

Check callback-head alignment and reject NULL callback
functions in Tiny RCU's call_rcu() path.

Signed-off-by: Kunwu Chan <chentao@xxxxxxxxxx>
---
 kernel/rcu/tiny.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/kernel/rcu/tiny.c b/kernel/rcu/tiny.c
index bd22fa43108d..ef0b0474f207 100644
--- a/kernel/rcu/tiny.c
+++ b/kernel/rcu/tiny.c
@@ -252,6 +252,13 @@ EXPORT_SYMBOL_GPL(synchronize_rcu);
  */
 void call_rcu(struct rcu_head *head, rcu_callback_t func)
 {
+	/* 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;
+
 	/* Record the caller: the irq_work's stack says nothing about it. */
 	kasan_record_aux_stack(head);
 
-- 
2.43.0