net: hsr: fix suspicious RCU usage warning in hsr_node_get_first()

When hsr_create_self_node() calls hsr_node_get_first(), the suspicious
RCU usage warning is occurred. The reason why this warning is raised is
the callers of hsr_node_get_first() use rcu_read_lock_bh() and
other different synchronization mechanisms. Thus, this patch solved by
replacing rcu_dereference() with rcu_dereference_bh_check().

The kernel test robot reports:
    [   50.083470][ T3596] =============================
    [   50.088648][ T3596] WARNING: suspicious RCU usage
    [   50.093785][ T3596] 5.17.0-rc3-next-20220208-syzkaller #0 Not tainted
    [   50.100669][ T3596] -----------------------------
    [   50.105513][ T3596] net/hsr/hsr_framereg.c:34 suspicious rcu_dereference_check() usage!
    [   50.113799][ T3596]
    [   50.113799][ T3596] other info that might help us debug this:
    [   50.113799][ T3596]
    [   50.124257][ T3596]
    [   50.124257][ T3596] rcu_scheduler_active = 2, debug_locks = 1
    [   50.132368][ T3596] 2 locks held by syz-executor.0/3596:
    [   50.137863][ T3596]  #0: ffffffff8d3357e8 (rtnl_mutex){+.+.}-{3:3}, at: rtnetlink_rcv_msg+0x3be/0xb80
    [   50.147470][ T3596]  #1: ffff88807ec9d5f0 (&hsr->list_lock){+...}-{2:2}, at: hsr_create_self_node+0x225/0x650
    [   50.157623][ T3596]
    [   50.157623][ T3596] stack backtrace:
    [   50.163510][ T3596] CPU: 1 PID: 3596 Comm: syz-executor.0 Not tainted 5.17.0-rc3-next-20220208-syzkaller #0
    [   50.173381][ T3596] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
    [   50.183623][ T3596] Call Trace:
    [   50.186904][ T3596]  <TASK>
    [   50.189844][ T3596]  dump_stack_lvl+0xcd/0x134
    [   50.194640][ T3596]  hsr_node_get_first+0x9b/0xb0
    [   50.199499][ T3596]  hsr_create_self_node+0x22d/0x650
    [   50.204688][ T3596]  hsr_dev_finalize+0x2c1/0x7d0
    [   50.209669][ T3596]  hsr_newlink+0x315/0x730
    [   50.214113][ T3596]  ? hsr_dellink+0x130/0x130
    [   50.218789][ T3596]  ? rtnl_create_link+0x7e8/0xc00
    [   50.223803][ T3596]  ? hsr_dellink+0x130/0x130
    [   50.228397][ T3596]  __rtnl_newlink+0x107c/0x1760
    [   50.233249][ T3596]  ? rtnl_setlink+0x3c0/0x3c0
    [   50.238043][ T3596]  ? is_bpf_text_address+0x77/0x170
    [   50.243362][ T3596]  ? lock_downgrade+0x6e0/0x6e0
    [   50.248219][ T3596]  ? unwind_next_frame+0xee1/0x1ce0
    [   50.253605][ T3596]  ? entry_SYSCALL_64_after_hwframe+0x44/0xae
    [   50.259669][ T3596]  ? __sanitizer_cov_trace_cmp4+0x1c/0x70
    [   50.265423][ T3596]  ? is_bpf_text_address+0x99/0x170
    [   50.270819][ T3596]  ? kernel_text_address+0x39/0x80
    [   50.275950][ T3596]  ? __kernel_text_address+0x9/0x30
    [   50.281336][ T3596]  ? unwind_get_return_address+0x51/0x90
    [   50.286975][ T3596]  ? create_prof_cpu_mask+0x20/0x20
    [   50.292178][ T3596]  ? arch_stack_walk+0x93/0xe0
    [   50.297172][ T3596]  ? kmem_cache_alloc_trace+0x42/0x2c0
    [   50.302637][ T3596]  ? rcu_read_lock_sched_held+0x3a/0x70
    [   50.308194][ T3596]  rtnl_newlink+0x64/0xa0
    [   50.312524][ T3596]  ? __rtnl_newlink+0x1760/0x1760
    [   50.317545][ T3596]  rtnetlink_rcv_msg+0x413/0xb80
    [   50.322631][ T3596]  ? rtnl_newlink+0xa0/0xa0
    [   50.327159][ T3596]  netlink_rcv_skb+0x153/0x420
    [   50.331931][ T3596]  ? rtnl_newlink+0xa0/0xa0
    [   50.336436][ T3596]  ? netlink_ack+0xa80/0xa80
    [   50.341095][ T3596]  ? netlink_deliver_tap+0x1a2/0xc40
    [   50.346532][ T3596]  ? netlink_deliver_tap+0x1b1/0xc40
    [   50.351839][ T3596]  netlink_unicast+0x539/0x7e0
    [   50.356633][ T3596]  ? netlink_attachskb+0x880/0x880
    [   50.361750][ T3596]  ? __sanitizer_cov_trace_const_cmp8+0x1d/0x70
    [   50.368003][ T3596]  ? __sanitizer_cov_trace_const_cmp8+0x1d/0x70
    [   50.374707][ T3596]  ? __phys_addr_symbol+0x2c/0x70
    [   50.379753][ T3596]  ? __sanitizer_cov_trace_cmp8+0x1d/0x70
    [   50.385568][ T3596]  ? __check_object_size+0x16c/0x4f0
    [   50.390859][ T3596]  netlink_sendmsg+0x904/0xe00
    [   50.395715][ T3596]  ? netlink_unicast+0x7e0/0x7e0
    [   50.400722][ T3596]  ? __sanitizer_cov_trace_const_cmp4+0x1c/0x70
    [   50.407003][ T3596]  ? netlink_unicast+0x7e0/0x7e0
    [   50.412119][ T3596]  sock_sendmsg+0xcf/0x120
    [   50.416548][ T3596]  __sys_sendto+0x21c/0x320
    [   50.421052][ T3596]  ? __ia32_sys_getpeername+0xb0/0xb0
    [   50.426427][ T3596]  ? lockdep_hardirqs_on_prepare+0x400/0x400
    [   50.432721][ T3596]  ? __context_tracking_exit+0xb8/0xe0
    [   50.438188][ T3596]  ? lock_downgrade+0x6e0/0x6e0
    [   50.443041][ T3596]  ? lock_downgrade+0x6e0/0x6e0
    [   50.447902][ T3596]  __x64_sys_sendto+0xdd/0x1b0
    [   50.452759][ T3596]  ? lockdep_hardirqs_on+0x79/0x100
    [   50.457964][ T3596]  ? syscall_enter_from_user_mode+0x21/0x70
    [   50.464150][ T3596]  do_syscall_64+0x35/0xb0
    [   50.468565][ T3596]  entry_SYSCALL_64_after_hwframe+0x44/0xae
    [   50.474452][ T3596] RIP: 0033:0x7f3148504e1c
    [   50.479052][ T3596] Code: fa fa ff ff 44 8b 4c 24 2c 4c 8b 44 24 20 89 c5 44 8b 54 24 28 48 8b 54 24 18 b8 2c 00 00 00 48 8b 74 24 10 8b 7c 24 08 0f 05 <48> 3d 00 f0 ff ff 77 34 89 ef 48 89 44 24 08 e8 20 fb ff ff 48 8b
    [   50.498926][ T3596] RSP: 002b:00007ffeab5f2ab0 EFLAGS: 00000293 ORIG_RAX: 000000000000002c
    [   50.507342][ T3596] RAX: ffffffffffffffda RBX: 00007f314959d320 RCX: 00007f3148504e1c
    [   50.515393][ T3596] RDX: 0000000000000048 RSI: 00007f314959d370 RDI: 0000000000000003
    [   50.523444][ T3596] RBP: 0000000000000000 R08: 00007ffeab5f2b04 R09: 000000000000000c
    [   50.531492][ T3596] R10: 0000000000000000 R11: 0000000000000293 R12: 0000000000000000
    [   50.539455][ T3596] R13: 00007f314959d370 R14: 0000000000000003 R15: 0000000000000000

Fixes: 4acc45db ("net: hsr: use hlist_head instead of list_head for mac addresses")
Reported-by: Eric Dumazet <eric.dumazet@gmail.com>
Reported-and-tested-by: syzbot+f0eb4f3876de066b128c@syzkaller.appspotmail.com
Signed-off-by: Juhee Kang <claudiajkang@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/hsr/hsr_framereg.c

@@ -27,11 +27,11 @@ u32 hsr_mac_hash(struct hsr_priv *hsr, const unsigned char *addr)
 	return reciprocal_scale(hash, hsr->hash_buckets);
 }
 
-struct hsr_node *hsr_node_get_first(struct hlist_head *head)
+struct hsr_node *hsr_node_get_first(struct hlist_head *head, int cond)
 {
 	struct hlist_node *first;
 
-	first = rcu_dereference(hlist_first_rcu(head));
+	first = rcu_dereference_bh_check(hlist_first_rcu(head), cond);
 	if (first)
 		return hlist_entry(first, struct hsr_node, mac_list);
 
@@ -59,7 +59,8 @@ bool hsr_addr_is_self(struct hsr_priv *hsr, unsigned char *addr)
 {
 	struct hsr_node *node;
 
-	node = hsr_node_get_first(&hsr->self_node_db);
+	node = hsr_node_get_first(&hsr->self_node_db,
+				  lockdep_is_held(&hsr->list_lock));
 	if (!node) {
 		WARN_ONCE(1, "HSR: No self node\n");
 		return false;
@@ -106,7 +107,8 @@ int hsr_create_self_node(struct hsr_priv *hsr,
 	ether_addr_copy(node->macaddress_B, addr_b);
 
 	spin_lock_bh(&hsr->list_lock);
-	oldnode = hsr_node_get_first(self_node_db);
+	oldnode = hsr_node_get_first(self_node_db,
+				     lockdep_is_held(&hsr->list_lock));
 	if (oldnode) {
 		hlist_replace_rcu(&oldnode->mac_list, &node->mac_list);
 		spin_unlock_bh(&hsr->list_lock);
@@ -125,7 +127,8 @@ void hsr_del_self_node(struct hsr_priv *hsr)
 	struct hsr_node *node;
 
 	spin_lock_bh(&hsr->list_lock);
-	node = hsr_node_get_first(self_node_db);
+	node = hsr_node_get_first(self_node_db,
+				  lockdep_is_held(&hsr->list_lock));
 	if (node) {
 		hlist_del_rcu(&node->mac_list);
 		kfree_rcu(node, rcu_head);
@@ -597,7 +600,8 @@ void *hsr_get_next_node(struct hsr_priv *hsr, void *_pos,
 	hash = hsr_mac_hash(hsr, addr);
 
 	if (!_pos) {
-		node = hsr_node_get_first(&hsr->node_db[hash]);
+		node = hsr_node_get_first(&hsr->node_db[hash],
+					  lockdep_is_held(&hsr->list_lock));
 		if (node)
 			ether_addr_copy(addr, node->macaddress_A);
 		return node;

net/hsr/hsr_framereg.h

@@ -29,7 +29,7 @@ struct hsr_frame_info {
 };
 
 u32 hsr_mac_hash(struct hsr_priv *hsr, const unsigned char *addr);
-struct hsr_node *hsr_node_get_first(struct hlist_head *head);
+struct hsr_node *hsr_node_get_first(struct hlist_head *head, int cond);
 void hsr_del_self_node(struct hsr_priv *hsr);
 void hsr_del_nodes(struct hlist_head *node_db);
 struct hsr_node *hsr_get_node(struct hsr_port *port, struct hlist_head *node_db,