# Re: route.c:645 suspicious rcu\_dereference\_check()

- From: Eric Dumazet \<hidden\>
- Date: 2012-08-31 11:50:17 
- List: netdev
- Page: https://ratatoskr.run/netdev/2012/08/10903000
- Thread: https://ratatoskr.run/netdev/2012/08/10902836/t.md

```text
On Thu, 2012-08-30 at 13:34 -0400, David Miller wrote:
> From: Eric Dumazet <redacted>
> Date: Tue, 28 Aug 2012 15:33:07 -0700
> 
> > From: Eric Dumazet <redacted>
> > 
> > [PATCH] ipv4: must use rcu protection while calling fib_lookup
> > 
> > Following lockdep splat was reported by Pavel Roskin :
>  ...
> > Signed-off-by: Eric Dumazet <redacted>
> > Reported-by: Pavel Roskin <redacted>
> 
> Applied, thanks.
> 
> It looks like the redirect handlers might have the same problem?

Hi David

Correct me if I am wrong, but redirect handlers should all run under
rcu_read_lock() protection already.

rcu_read_lock() is done in ip_local_deliver_finish() or
ip_rt_send_redirect() for the forward path.

And above of them, we also have rcu_read_lock() done in
__netif_receive_skb()
```