netdev - Re: Kernel memory corruption in CIPSO labeled TCP packets processing.

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Message-ID: <CAHC9VhRXc=UAfNidPjYsG561_kc_j2CkD6Db=Kb=Gjyhk3ko6Q@mail.gmail.com>
Date:   Tue, 29 Jan 2019 17:42:24 -0500
From:   Paul Moore <paul@...l-moore.com>
To:     Nazarov Sergey <s-nazarov@...dex.ru>
Cc:     "linux-security-module@...r.kernel.org" 
        <linux-security-module@...r.kernel.org>,
        "selinux@...r.kernel.org" <selinux@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Casey Schaufler <casey@...aufler-ca.com>
Subject: Re: Kernel memory corruption in CIPSO labeled TCP packets processing.

On Tue, Jan 29, 2019 at 2:23 AM Nazarov Sergey <s-nazarov@...dex.ru> wrote:
> 29.01.2019, 01:18, "Paul Moore" <paul@...l-moore.com>:
> > If we don't pass a skb into ip_options_compile(), meaning both "skb"
> > and "rt" will be NULL, then I don't believe the option data will
> > change. Am I missing something?
>
> I mean, in cipso_v4_error we copy option data from skb before ip_options_compile call:
> +       memcpy(opt->__data, (unsigned char *)&(ip_hdr(skb)[1]), opt->optlen);
> But skb IP header data could be already changed by first call of ip_options_compile
> when packet received.

There are several cases where the stack ends up calling icmp_send()
after the skb has been through ip_options_compile(), that should be
okay.

-- 
paul moore
www.paul-moore.com