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

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Message-Id: <20170913.093428.806129519464331602.davem@davemloft.net>
Date:   Wed, 13 Sep 2017 09:34:28 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     jiri@...nulli.us
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

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.