netdev - Re: [Patch net] net_sched: check error pointer in tcf_dump

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Message-Id: <20201004.145453.1397904175583154013.davem@davemloft.net>
Date:   Sun, 04 Oct 2020 14:54:53 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     xiyou.wangcong@...il.com
Cc:     netdev@...r.kernel.org,
        syzbot+b47bc4f247856fb4d9e1@...kaller.appspotmail.com,
        vladbu@...lanox.com, jhs@...atatu.com, jiri@...nulli.us
Subject: Re: [Patch net] net_sched: check error pointer in tcf_dump_walker()

From: Cong Wang <xiyou.wangcong@...il.com>
Date: Fri,  2 Oct 2020 12:13:34 -0700

> Although we take RTNL on dump path, it is possible to
> skip RTNL on insertion path. So the following race condition
> is possible:
> 
> rtnl_lock()		// no rtnl lock
> 			mutex_lock(&idrinfo->lock);
> 			// insert ERR_PTR(-EBUSY)
> 			mutex_unlock(&idrinfo->lock);
> tc_dump_action()
> rtnl_unlock()
> 
> So we have to skip those temporary -EBUSY entries on dump path
> too.
> 
> Reported-and-tested-by: syzbot+b47bc4f247856fb4d9e1@...kaller.appspotmail.com
> Fixes: 0fedc63fadf0 ("net_sched: commit action insertions together")
> Cc: Vlad Buslov <vladbu@...lanox.com>
> 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.