netdev - Re: [Patch net-next 1/2] net_sched: fix a race condition in tcindex

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Date:   Wed, 20 Feb 2019 20:11:52 -0800 (PST)
From:   David Miller <davem@...emloft.net>
To:     xiyou.wangcong@...il.com
Cc:     netdev@...r.kernel.org, bugs@...elecom.ro, ben@...adent.org.uk,
        jhs@...atatu.com, jiri@...nulli.us
Subject: Re: [Patch net-next 1/2] net_sched: fix a race condition in
 tcindex_destroy()

From: Cong Wang <xiyou.wangcong@...il.com>
Date: Sat, 16 Feb 2019 10:58:26 -0800

> (cherry picked from commit 8015d93ebd27484418d4952284fd02172fa4b0b2)
> 
> tcindex_destroy() invokes tcindex_destroy_element() via
> a walker to delete each filter result in its perfect hash
> table, and tcindex_destroy_element() calls tcindex_delete()
> which schedules tcf RCU works to do the final deletion work.
> Unfortunately this races with the RCU callback
> __tcindex_destroy(), which could lead to use-after-free as
> reported by Adrian.
> 
> Fix this by migrating this RCU callback to tcf RCU work too,
> as that workqueue is ordered, we will not have use-after-free.
> 
> Note, we don't need to hold netns refcnt because we don't call
> tcf_exts_destroy() here.
> 
> Fixes: 27ce4f05e2ab ("net_sched: use tcf_queue_work() in tcindex filter")
> Reported-by: Adrian <bugs@...elecom.ro>
> Cc: Ben Hutchings <ben@...adent.org.uk>
> Cc: Jamal Hadi Salim <jhs@...atatu.com>
> Cc: Jiri Pirko <jiri@...nulli.us>
> Signed-off-by: Cong Wang <xiyou.wangcong@...il.com>

Applied.