netdev - Re: [PATCH v1 0/4] iptables: Module unload causing NULL pointer reference.

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Date:   Wed, 24 Jun 2020 14:05:49 +0200
From:   Pablo Neira Ayuso <pablo@...filter.org>
To:     David Wilder <dwilder@...ibm.com>
Cc:     netdev@...r.kernel.org, netfilter-devel@...r.kernel.org,
        fw@...len.de, wilder@...ibm.com, mkubecek@...e.com
Subject: Re: [PATCH v1 0/4] iptables: Module unload causing NULL pointer
 reference.

On Mon, Jun 22, 2020 at 10:10:10AM -0700, David Wilder wrote:
> A crash happened on ppc64le when running ltp network tests triggered by "rmmod iptable_mangle".
> 
> See previous discussion in this thread: https://lists.openwall.net/netdev/2020/06/03/161 .
> 
> In the crash I found in iptable_mangle_hook() that state->net->ipv4.iptable_mangle=NULL causing a NULL pointer dereference. net->ipv4.iptable_mangle is set to NULL in iptable_mangle_net_exit() and called when ip_mangle modules is unloaded. A rmmod task was found running in the crash dump.  A 2nd crash showed the same problem when running "rmmod iptable_filter" (net->ipv4.iptable_filter=NULL).
> 
> To fix this I added .pre_exit hook in all iptable_foo.c. The pre_exit will un-register the underlying hook and exit would do the table freeing. The netns core does an unconditional synchronize_rcu after the pre_exit hooks insuring no packets are in flight that have picked up the pointer before completing the un-register.
> 
> These patches include changes for both iptables and ip6tables.
> 
> We tested this fix with ltp running iptables01.sh and iptables01.sh -6 a loop for 72 hours.

Series applied, thanks.