netdev - Re: [Patch net] net_sched: hold rtnl lock in tcindex_partial_destroy

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Message-Id: <20200314.204203.716262950775446891.davem@davemloft.net>
Date:   Sat, 14 Mar 2020 20:42:03 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     xiyou.wangcong@...il.com
Cc:     netdev@...r.kernel.org,
        syzbot+653090db2562495901dc@...kaller.appspotmail.com,
        jhs@...atatu.com, jiri@...nulli.us
Subject: Re: [Patch net] net_sched: hold rtnl lock in
 tcindex_partial_destroy_work()

From: Cong Wang <xiyou.wangcong@...il.com>
Date: Wed, 11 Mar 2020 22:42:27 -0700

> syzbot reported a use-after-free in tcindex_dump(). This is due to
> the lack of RTNL in the deferred rcu work. We queue this work with
> RTNL in tcindex_change(), later, tcindex_dump() is called:
> 
>         fh = tp->ops->get(tp, t->tcm_handle);
> 	...
>         err = tp->ops->change(..., &fh, ...);
>         tfilter_notify(..., fh, ...);
> 
> but there is nothing to serialize the pending
> tcindex_partial_destroy_work() with tcindex_dump().
> 
> Fix this by simply holding RTNL in tcindex_partial_destroy_work(),
> so that it won't be called until RTNL is released after
> tc_new_tfilter() is completed.
> 
> Reported-and-tested-by: syzbot+653090db2562495901dc@...kaller.appspotmail.com
> Fixes: 3d210534cc93 ("net_sched: fix a race condition in tcindex_destroy()")
> Cc: Jamal Hadi Salim <jhs@...atatu.com>
> Cc: Jiri Pirko <jiri@...nulli.us>
> Signed-off-by: Cong Wang <xiyou.wangcong@...il.com>

Applied and queued up for -stable, thanks Cong.