netdev - Re: [patch net] net: sched: fix use-after-free in tcf_action_destroy and tcf_del

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Message-ID: <20170913205006.GD1981@nanopsycho>
Date:   Wed, 13 Sep 2017 22:50:06 +0200
From:   Jiri Pirko <jiri@...nulli.us>
To:     David Miller <davem@...emloft.net>
Cc:     netdev@...r.kernel.org, jhs@...atatu.com, xiyou.wangcong@...il.com,
        kubakici@...pl, mlxsw@...lanox.com
Subject: Re: [patch net] net: sched: fix use-after-free in tcf_action_destroy
 and tcf_del_walker

Wed, Sep 13, 2017 at 06:34:28PM CEST, davem@...emloft.net wrote:
>From: Jiri Pirko <jiri@...nulli.us>
>Date: Wed, 13 Sep 2017 17:32:37 +0200
>
>> From: Jiri Pirko <jiri@...lanox.com>
>> 
>> Recent commit d7fb60b9cafb ("net_sched: get rid of tcfa_rcu") removed
>> freeing in call_rcu, which changed already existing hard-to-hit
>> race condition into 100% hit:
>> 
>> [  598.599825] BUG: unable to handle kernel NULL pointer dereference at 0000000000000030
>> [  598.607782] IP: tcf_action_destroy+0xc0/0x140
>> 
>> Or:
>> 
>> [   40.858924] BUG: unable to handle kernel NULL pointer dereference at 0000000000000030
>> [   40.862840] IP: tcf_generic_walker+0x534/0x820
>> 
>> Fix this by storing the ops and use them directly for module_put call.
>> 
>> Fixes: a85a970af265 ("net_sched: move tc_action into tcf_common")
>> Signed-off-by: Jiri Pirko <jiri@...lanox.com>
>
>Applied, thanks Jiri.

Oh, I forgot to mention, this would be nice to push to stable.