netdev - Re: Suspicious RCU usage in bridge with Linux v4.0-9362-g1fc149933fd4

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Message-ID: <1431355986.566.18.camel@edumazet-glaptop2.roam.corp.google.com>
Date:	Mon, 11 May 2015 07:53:06 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Dominick Grift <dac.override@...il.com>
Cc:	netdev@...r.kernel.org
Subject: Re: Suspicious RCU usage in bridge with Linux
 v4.0-9362-g1fc149933fd4

On Mon, 2015-05-11 at 15:15 +0200, Dominick Grift wrote:
> On Mon, May 04, 2015 at 02:35:27PM -0700, Cong Wang wrote:
> 
> <snip>
> 
> > It _looks like_ we only retrieve vlan info to fill netlink
> > messages in timer context, so it doesn't seem we need to
> > hold br->lock here.
> > 
> > But I never look into br vlan code of course.
> 
> This is just a friendly reminder that this issue still exits in: 4.1.0-0.rc2.git3.1
> 
> Ignore me if you are aware of the above
> 

Hi Dominick

Have you tried this patch I sent last monday ?

I will submit formally when I get a test result.

Thanks

diff --git a/net/bridge/br_stp_timer.c b/net/bridge/br_stp_timer.c
index 4fcaa67750fda845ad0a180332c4cd96a9524086..7caf7fae2d5b8aa369b924e1c87a47c343fb8954 100644
--- a/net/bridge/br_stp_timer.c
+++ b/net/bridge/br_stp_timer.c
@@ -97,7 +97,9 @@ static void br_forward_delay_timer_expired(unsigned long arg)
 		netif_carrier_on(br->dev);
 	}
 	br_log_state(p);
+	rcu_read_lock();
 	br_ifinfo_notify(RTM_NEWLINK, p);
+	rcu_read_unlock();
 	spin_unlock(&br->lock);
 }
 


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