netdev - Re: [PATCH v2 net] net/ipv4: defensive cipso option parsing

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Date:   Mon, 17 Sep 2018 19:38:48 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     snu@...zon.com
Cc:     netdev@...r.kernel.org, aams@...zon.de, dwmw@...zon.co.uk,
        yujuan.qi@...iatek.com, paul@...l-moore.com, sveith@...zon.de,
        stable@...r.kernel.org
Subject: Re: [PATCH v2 net] net/ipv4: defensive cipso option parsing

From: Stefan Nuernberger <snu@...zon.com>
Date: Mon, 17 Sep 2018 19:46:53 +0200

> commit 40413955ee26 ("Cipso: cipso_v4_optptr enter infinite loop") fixed
> a possible infinite loop in the IP option parsing of CIPSO. The fix
> assumes that ip_options_compile filtered out all zero length options and
> that no other one-byte options beside IPOPT_END and IPOPT_NOOP exist.
> While this assumption currently holds true, add explicit checks for zero
> length and invalid length options to be safe for the future. Even though
> ip_options_compile should have validated the options, the introduction of
> new one-byte options can still confuse this code without the additional
> checks.
> 
> Signed-off-by: Stefan Nuernberger <snu@...zon.com>

Applied to net-next.

This is not 'net' nor -stable material.  I'm hesitent about this
change as-is, and ip_options_compile() is not changing semantics in
-stable in the way that you say can cause problems.