[PATCH 4/9] srcu: Validate callback arguments

[Kunwu Chan]

Check callback-head alignment and reject NULL callback
functions in the SRCU callback registration paths.

Signed-off-by: Kunwu Chan <chentao@xxxxxxxxxx>
---
 kernel/rcu/srcutiny.c | 7 +++++++
 kernel/rcu/srcutree.c | 7 +++++++
 2 files changed, 14 insertions(+)

diff --git a/kernel/rcu/srcutiny.c b/kernel/rcu/srcutiny.c
index 3ee28885b96f..98864977bed2 100644
--- a/kernel/rcu/srcutiny.c
+++ b/kernel/rcu/srcutiny.c
@@ -291,6 +291,13 @@ EXPORT_SYMBOL_GPL(srcu_defer_drain);
 void call_srcu(struct srcu_struct *ssp, struct rcu_head *rhp,
 	       rcu_callback_t func)
 {
+	/* Misaligned rcu_head! */
+	WARN_ON_ONCE((unsigned long)rhp & (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(rhp);
 
diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c
index 46fe2f0cef85..1993ddbdb828 100644
--- a/kernel/rcu/srcutree.c
+++ b/kernel/rcu/srcutree.c
@@ -1529,6 +1529,13 @@ static void srcu_do_enqueue(struct srcu_struct *ssp, struct rcu_head *rhp,
 static void __call_srcu(struct srcu_struct *ssp, struct rcu_head *rhp,
 			rcu_callback_t func, bool do_norm)
 {
+	/* Misaligned rcu_head! */
+	WARN_ON_ONCE((unsigned long)rhp & (sizeof(void *) - 1));
+
+	/* Avoid NULL dereference if callback is NULL. */
+	if (WARN_ON_ONCE(!func))
+		return;
+
 	if (WARN_ON_ONCE(ssp->srcu_reader_flavor == SRCU_READ_FLAVOR_ATOMIC))
 		return; // Leak the callback rather than corrupt SRCU state.
 
-- 
2.43.0