netdev - Re: [PATCH net-next] net/sched: cls_flower: verify root pointer before dereferncing it

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Message-Id: <20161122.103742.1421376877129949203.davem@davemloft.net>
Date:   Tue, 22 Nov 2016 10:37:42 -0500 (EST)
From:   David Miller <davem@...emloft.net>
To:     jiri@...nulli.us
Cc:     roid@...lanox.com, netdev@...r.kernel.org, jiri@...lanox.com,
        xiyou.wangcong@...il.com, ogerlitz@...lanox.com,
        cwang@...pensource.com
Subject: Re: [PATCH net-next] net/sched: cls_flower: verify root pointer
 before dereferncing it

From: Jiri Pirko <jiri@...nulli.us>
Date: Tue, 22 Nov 2016 15:48:44 +0100

> Tue, Nov 22, 2016 at 03:25:26PM CET, roid@...lanox.com wrote:
>>tp->root is being allocated in init() time and kfreed in destroy()
>>however it is being dereferenced in classify() path.
>>
>>We could be in classify() path after destroy() was called and thus 
>>tp->root is null. Verifying if tp->root is null in classify() path 
>>is enough because it's being freed with kfree_rcu() and classify() 
>>path is under rcu_read_lock().
>>
>>Fixes: 1e052be69d04 ("net_sched: destroy proto tp when all filters are gone")
>>Signed-off-by: Roi Dayan <roid@...lanox.com>
>>Cc: Cong Wang <cwang@...pensource.com>
> 
> This is correct
> 
> Reviewed-by: Jiri Pirko <jiri@...lanox.com>
> 
> The other way to fix this would be to move tp->ops->destroy call to
> call_rcu phase. That would require bigger changes though. net-next
> perhaps?

This patch is targetted at net-next as per Subj.