netdev - Re: [PATCH 07/23] netfilter: x_tables: check standard target size too

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Message-ID: <8760tn5ojb.fsf@linux-m68k.org>
Date:	Sun, 05 Jun 2016 23:11:36 +0200
From:	Andreas Schwab <schwab@...ux-m68k.org>
To:	Pablo Neira Ayuso <pablo@...filter.org>
Cc:	netfilter-devel@...r.kernel.org, davem@...emloft.net,
	netdev@...r.kernel.org
Subject: Re: [PATCH 07/23] netfilter: x_tables: check standard target size too

Pablo Neira Ayuso <pablo@...filter.org> writes:

> From: Florian Westphal <fw@...len.de>
>
> We have targets and standard targets -- the latter carries a verdict.
>
> The ip/ip6tables validation functions will access t->verdict for the
> standard targets to fetch the jump offset or verdict for chainloop
> detection, but this happens before the targets get checked/validated.
>
> Thus we also need to check for verdict presence here, else t->verdict
> can point right after a blob.
>
> Spotted with UBSAN while testing malformed blobs.

This breaks iptables on PPC32.

# iptables -nL
iptables v1.4.21: can't initialize iptables table `filter': Table does not exist (do you need to insmod?)
Perhaps iptables or your kernel needs to be upgraded.
# modprobe iptable-filter
FATAL: Error inserting iptable_filter (/lib/modules/4.7.0-rc1/kernel/net/ipv4/netfilter/iptable_filter.ko): Invalid argument

Andreas.

-- 
Andreas Schwab, schwab@...ux-m68k.org
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"And now for something completely different."