* [PATCH nf] netfilter: egress: silence egress hook lockdep splats
@ 2022-02-28 3:18 Florian Westphal
2022-02-28 21:34 ` Pablo Neira Ayuso
0 siblings, 1 reply; 2+ messages in thread
From: Florian Westphal @ 2022-02-28 3:18 UTC (permalink / raw)
To: netfilter-devel; +Cc: Florian Westphal, Eric Dumazet
Netfilter assumes its called with rcu_read_lock held, but in egress
hook case it may be called with BH readlock.
This triggers lockdep splat.
In order to avoid to change all rcu_dereference() to
rcu_dereference_check(..., rcu_read_lock_bh_held()), wrap nf_hook_slow
with read lock/unlock pair.
Reported-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: Florian Westphal <fw@strlen.de>
---
include/linux/netfilter_netdev.h | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/include/linux/netfilter_netdev.h b/include/linux/netfilter_netdev.h
index b4dd96e4dc8d..e6487a691136 100644
--- a/include/linux/netfilter_netdev.h
+++ b/include/linux/netfilter_netdev.h
@@ -101,7 +101,11 @@ static inline struct sk_buff *nf_hook_egress(struct sk_buff *skb, int *rc,
nf_hook_state_init(&state, NF_NETDEV_EGRESS,
NFPROTO_NETDEV, dev, NULL, NULL,
dev_net(dev), NULL);
+
+ /* nf assumes rcu_read_lock, not just read_lock_bh */
+ rcu_read_lock();
ret = nf_hook_slow(skb, &state, e, 0);
+ rcu_read_unlock();
if (ret == 1) {
return skb;
--
2.34.1
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH nf] netfilter: egress: silence egress hook lockdep splats
2022-02-28 3:18 [PATCH nf] netfilter: egress: silence egress hook lockdep splats Florian Westphal
@ 2022-02-28 21:34 ` Pablo Neira Ayuso
0 siblings, 0 replies; 2+ messages in thread
From: Pablo Neira Ayuso @ 2022-02-28 21:34 UTC (permalink / raw)
To: Florian Westphal; +Cc: netfilter-devel, Eric Dumazet
On Mon, Feb 28, 2022 at 04:18:05AM +0100, Florian Westphal wrote:
> Netfilter assumes its called with rcu_read_lock held, but in egress
> hook case it may be called with BH readlock.
>
> This triggers lockdep splat.
>
> In order to avoid to change all rcu_dereference() to
> rcu_dereference_check(..., rcu_read_lock_bh_held()), wrap nf_hook_slow
> with read lock/unlock pair.
Applied, thanks
^ permalink raw reply [flat|nested] 2+ messages in thread
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