linux-kernel - Re: [PATCH v2] notifier: Fix soft lockup for notifier_call

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Message-ID: <1467095271.6850.192.camel@edumazet-glaptop3.roam.corp.google.com>
Date:	Tue, 28 Jun 2016 08:27:51 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Ding Tianhong <dingtianhong@...wei.com>
Cc:	luto@...nel.org, mingo@...nel.org, linux-kernel@...r.kernel.org,
	Eric Dumazet <edumazet@...gle.com>,
	"David S. Miller" <davem@...emloft.net>,
	Netdev <netdev@...r.kernel.org>,
	Cong Wang <cwang@...pensource.com>
Subject: Re: [PATCH v2] notifier: Fix soft lockup for notifier_call_chain().

On Tue, 2016-06-28 at 08:22 +0200, Eric Dumazet wrote:

> Follow the stack trace and add another cond_resched() where it is needed
> then ?
> 
> Lot of this code was written decade ago where nobody expected a root
> user was going to try hard to crash its host ;)
> 
> I did not check if the following is valid (Maybe __fib6_clean_all() is
> called with some spinlock/rwlock held)

Well, fib6_run_gc() can call it with
spin_lock_bh(&net->ipv6.fib6_gc_lock) so this wont work.

We need more invasive changes.