netdev - Re: [PATCH net] rhashtable: prevent work queue schedule while dismantling

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Date:   Mon, 1 Oct 2018 21:40:22 +0800
From:   Herbert Xu <herbert@...dor.apana.org.au>
To:     Eric Dumazet <edumazet@...gle.com>
Cc:     "David S . Miller" <davem@...emloft.net>,
        netdev <netdev@...r.kernel.org>,
        Eric Dumazet <eric.dumazet@...il.com>,
        Thomas Graf <tgraf@...g.ch>
Subject: Re: [PATCH net] rhashtable: prevent work queue schedule while
 dismantling

On Mon, Oct 01, 2018 at 06:16:27AM -0700, Eric Dumazet wrote:
> syszbot found an interesting use-after-free [1] happening
> while IPv4 fragment rhashtable was destroyed at netns dismantle.
> 
> While no insertions can possibly happen at the time a dismantling
> netns is destroying this rhashtable, timers can still fire and
> attempt to remove elements from this rhashtable.

Hmm, I think that's your real problem.  rhashtable_free_and_destroy
doesn't take any locks with respect to the normal insertion/removal
path so it definitely isn't safe to call it while you're still
invoking the normal rhashtable remove function.

Cheers,
-- 
Email: Herbert Xu <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt