netdev - [PATCH net-next 18/32] netfilter: egress: avoid a lockdep splat

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Date:   Mon, 10 Jan 2022 00:16:26 +0100
From:   Pablo Neira Ayuso <pablo@...filter.org>
To:     netfilter-devel@...r.kernel.org
Cc:     davem@...emloft.net, netdev@...r.kernel.org, kuba@...nel.org
Subject: [PATCH net-next 18/32] netfilter: egress: avoid a lockdep splat

From: Florian Westphal <fw@...len.de>

include/linux/netfilter_netdev.h:97 suspicious rcu_dereference_check() usage!
2 locks held by sd-resolve/1100:
 0: ..(rcu_read_lock_bh){1:3}, at: ip_finish_output2
 1: ..(rcu_read_lock_bh){1:3}, at: __dev_queue_xmit
 __dev_queue_xmit+0 ..

The helper has two callers, one uses rcu_read_lock, the other
rcu_read_lock_bh().  Annotate the dereference to reflect this.

Fixes: 42df6e1d221dd ("netfilter: Introduce egress hook")
Signed-off-by: Florian Westphal <fw@...len.de>
Signed-off-by: Pablo Neira Ayuso <pablo@...filter.org>
---
 include/linux/netfilter_netdev.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/netfilter_netdev.h b/include/linux/netfilter_netdev.h
index b71b57a83bb4..b4dd96e4dc8d 100644
--- a/include/linux/netfilter_netdev.h
+++ b/include/linux/netfilter_netdev.h
@@ -94,7 +94,7 @@ static inline struct sk_buff *nf_hook_egress(struct sk_buff *skb, int *rc,
 		return skb;
 #endif
 
-	e = rcu_dereference(dev->nf_hooks_egress);
+	e = rcu_dereference_check(dev->nf_hooks_egress, rcu_read_lock_bh_held());
 	if (!e)
 		return skb;
 
-- 
2.30.2