[PATCH] NETWORKING: avoid use IPCB in cipso_v4_error

Paul Moore paul at paul-moore.com
Fri Feb 15 19:02:31 UTC 2019

On Thu, Feb 14, 2019 at 11:43 AM David Miller <davem at davemloft.net> wrote:
> From: Nazarov Sergey <s-nazarov at yandex.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 at yandex.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.

David, are you happy with Sergey's solution as a fix for this?

If so, would you prefer a respin of this patch to apply the to the
other broken callers (e.g. net/atm/clip.c), or would you rather merge
this patch and deal with the other callers in separate patches?

paul moore

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