[PATCH for-v7.5 05/11] srcu: Validate callback arguments

[Joel Fernandes <jfern@kernel.org>]

From: Kunwu Chan <kunwu.chan@gmail.com>

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

Reviewed-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Kunwu Chan <chentao@kylinos.cn>
Reviewed-by: Joel Fernandes <jfern@kernel.org>
Signed-off-by: Joel Fernandes <jfern@kernel.org>
---
 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..76f074f67299 100644
--- a/kernel/rcu/srcutree.c
+++ b/kernel/rcu/srcutree.c
@@ -1532,6 +1532,13 @@ static void __call_srcu(struct srcu_struct *ssp, struct rcu_head *rhp,
 	if (WARN_ON_ONCE(ssp->srcu_reader_flavor == SRCU_READ_FLAVOR_ATOMIC))
 		return; // Leak the callback rather than corrupt SRCU state.
 
+	/* 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);
 
-- 
2.54.0