Re: [syzbot] [bpf?] possible deadlock in kvfree_call_rcu

[Hillf Danton <hdanton@sina.com>]

On Wed, 27 Mar 2024 16:27:19 -0700
> syzbot has found a reproducer for the following issue on:
> 
> HEAD commit:    443574b03387 riscv, bpf: Fix kfunc parameters incompatibil..
> git tree:       bpf
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=16ca53c9180000

#syz test https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git  fe46a7dd189e

--- x/kernel/rcu/tree.c
+++ y/kernel/rcu/tree.c
@@ -5149,6 +5149,8 @@ static void __init rcu_dump_rcu_node_tre
 
 struct workqueue_struct *rcu_gp_wq;
 
+static DEFINE_PER_CPU(struct lock_class_key, krc_lock_key);
+
 static void __init kfree_rcu_batch_init(void)
 {
 	int cpu;
@@ -5169,6 +5171,11 @@ static void __init kfree_rcu_batch_init(
 
 	for_each_possible_cpu(cpu) {
 		struct kfree_rcu_cpu *krcp = per_cpu_ptr(&krc, cpu);
+		struct lock_class_key *key = per_cpu_ptr(&krc_lock_key, cpu);
+		char name[32] = {0};
+
+		sprintf(name, "krc%d", cpu);
+		lockdep_set_class_and_name(&krcp->lock, key, name);
 
 		for (i = 0; i < KFREE_N_BATCHES; i++) {
 			INIT_RCU_WORK(&krcp->krw_arr[i].rcu_work, kfree_rcu_work);
--