netdev - Re: [PATCH] NETWORKING: avoid use IPCB in cipso_v4

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Date:   Thu, 14 Feb 2019 21:14:03 +0300
From:   Nazarov Sergey <s-nazarov@...dex.ru>
To:     David Miller <davem@...emloft.net>
Cc:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-security-module@...r.kernel.org" 
        <linux-security-module@...r.kernel.org>,
        "kuznet@....inr.ac.ru" <kuznet@....inr.ac.ru>,
        "yoshfuji@...ux-ipv6.org" <yoshfuji@...ux-ipv6.org>,
        "paul@...l-moore.com" <paul@...l-moore.com>
Subject: Re: [PATCH] NETWORKING: avoid use IPCB in cipso_v4_error

Now the problem comes from TCP layer only. Is the IP over ATM operates over IP layer?

14.02.2019, 19:43, "David Miller" <davem@...emloft.net>:
> From: Nazarov Sergey <s-nazarov@...dex.ru>
> Date: Tue, 12 Feb 2019 18:10:03 +0300
>
>>  Since cipso_v4_error might be called from different network stack layers, we can't safely use icmp_send there.
>>  icmp_send copies IP options with ip_option_echo, which uses IPCB to take access to IP header compiled data.
>>  But after commit 971f10ec ("tcp: better TCP_SKB_CB layout to reduce cache line misses"), IPCB can't be used
>>  above IP layer.
>>  This patch fixes the problem by creating in cipso_v4_error a local copy of compiled IP options and using it with
>>  introduced __icmp_send function. This looks some overloaded, but in quite rare error conditions only.
>>
>>  The original discussion is here:
>>  https://lore.kernel.org/linux-security-module/16659801547571984@sas1-890ba5c2334a.qloud-c.yandex.net/
>>
>>  Signed-off-by: Sergey Nazarov <s-nazarov@...dex.ru>
>
> This problem is not unique to Cipso, net/atm/clip.c's error handler
> has the same exact issue.
>
> I didn't scan more of the tree, there are probably a couple more
> locations as well.