netdev - Re: [PATCH nf-next] netns: add and use net_ns

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Date:   Wed, 31 May 2017 12:55:27 -0400 (EDT)
From:   David Miller <davem@...emloft.net>
To:     fw@...len.de
Cc:     netfilter-devel@...r.kernel.org, netdev@...r.kernel.org,
        ebiederm@...ssion.com
Subject: Re: [PATCH nf-next] netns: add and use net_ns_barrier

From: Florian Westphal <fw@...len.de>
Date: Tue, 30 May 2017 11:38:12 +0200

> Quoting Joe Stringer:
>   If a user loads nf_conntrack_ftp, sends FTP traffic through a network
>   namespace, destroys that namespace then unloads the FTP helper module,
>   then the kernel will crash.
> 
> Events that lead to the crash:
> 1. conntrack is created with ftp helper in netns x
> 2. This netns is destroyed
> 3. netns destruction is scheduled
> 4. netns destruction wq starts, removes netns from global list
> 5. ftp helper is unloaded, which resets all helpers of the conntracks
> via for_each_net()
> 
> but because netns is already gone from list the for_each_net() loop
> doesn't include it, therefore all of these conntracks are unaffected.
> 
> 6. helper module unload finishes
> 7. netns wq invokes destructor for rmmod'ed helper
> 
> CC: "Eric W. Biederman" <ebiederm@...ssion.com>
> Reported-by: Joe Stringer <joe@....org>
> Signed-off-by: Florian Westphal <fw@...len.de>
> ---
>  Eric, I'd like an explicit (n)ack from you for this one.

Indeed, Eric, please do.

Otherwise I'm fine with the generic parts:

Acked-by: David S. Miller <davem@...emloft.net>