Re: [PATCH] NETWORKING: avoid use IPCB in cipso_v4_error

From: Paul Moore <paul@paul-moore.com>
Date: Fri, 15 Feb 2019 14:02:31 -0500

On Thu, Feb 14, 2019 at 11:43 AM David Miller [off-list ref] wrote:

quoted

From: Nazarov Sergey <redacted>
Date: Tue, 12 Feb 2019 18:10:03 +0300

quoted

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/ (local)

Signed-off-by: Sergey Nazarov <redacted>

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?

I'd like the other broken callers to be handled.