Re: [PATCH net-next 18/32] netfilter: egress: avoid a lockdep splat
From: Eric Dumazet <hidden>
Date: 2022-02-28 02:13:42
Also in:
netfilter-devel
On 1/9/22 15:16, Pablo Neira Ayuso wrote:
quoted hunk ↗ jump to hunk
From: Florian Westphal <fw@strlen.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@strlen.de> Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.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;
It seems other rcu_dereference() uses will also trigger lockdep splat. nft_do_chain() ... if (genbit) blob = rcu_dereference(chain->blob_gen_1); else blob = rcu_dereference(chain->blob_gen_0); I wonder how many other places will need a fix ?