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From: Florian Westphal <fw@strlen.de>
To: Stephen Smalley <sds@tycho.nsa.gov>
Cc: netdev@vger.kernel.org, linux-security-module@vger.kernel.org,
	selinux@tycho.nsa.gov, fw@strlen.de, davem@davemloft.net,
	herbert@gondor.apana.org.au, steffen.klassert@secunet.com,
	paul@paul-moore.com
Subject: Re: [RFC PATCH] xfrm: fix regression introduced by xdst pcpu cache
Date: Tue, 31 Oct 2017 12:11:22 +0100	[thread overview]
Message-ID: <20171031111122.GB7663@breakpoint.cc> (raw)
In-Reply-To: <20171030145843.13496-1-sds@tycho.nsa.gov>

Stephen Smalley <sds@tycho.nsa.gov> wrote:
> Since 4.14-rc1, the selinux-testsuite has been encountering sporadic
> failures during testing of labeled IPSEC. git bisect pointed to
> commit ec30d78c14a813db39a647b6a348b4286 ("xfrm: add xdst pcpu cache").
> The xdst pcpu cache is only checking that the policies are the same,
> but does not validate that the policy, state, and flow match with respect
> to security context labeling.  As a result, the wrong SA could be used
> and the receiver could end up performing permission checking and
> providing SO_PEERSEC or SCM_SECURITY values for the wrong security context.
> security_xfrm_state_pol_flow_match() exists for this purpose and is
> already called from xfrm_state_look_at() for matching purposes.
> Further, xfrm_state_look_at() also performs a xfrm_selector_match() test,
> which is also missing from the xdst pcpu cache logic.  Add calls to both
> of these functions when validating the cache entry.  With these changes,
> the selinux-testsuite passes all tests again.
> 
> Fixes: ec30d78c14a813db39a647b6a348b4286ba4abf5 ("xfrm: add xdst pcpu cache")
> Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>
> ---
> This is an RFC because I am not entirely confident in the fix, e.g. is it
> sufficient to perform this matching only on the first xfrm or do they all
> need to be walked as in xfrm_bundle_ok()?  Also, should we perform this
> matching before (as in this patch) or after calling xfrm_bundle_ok()? Also,
> do we need to test xfrm->sel.family before calling xfrm_selector_match
> (as in this patch) or not - xfrm_state_look_at() does so when the
> state is XFRM_STATE_VALID but not when it is _ERROR or _EXPIRED?

No idea.

I looked at the old flow cache but i don't see any of these extra
checks there either.

However, old flow cache stored flowi struct as key, and that contains a
flowi_secid,  populated by the decode_session hooks.

Was it enough to check for identical flowi_secid in the flowi structs to
avoid this problem or am i missing something?

WARNING: multiple messages have this Message-ID (diff)
From: fw@strlen.de (Florian Westphal)
To: linux-security-module@vger.kernel.org
Subject: [RFC PATCH] xfrm: fix regression introduced by xdst pcpu cache
Date: Tue, 31 Oct 2017 12:11:22 +0100	[thread overview]
Message-ID: <20171031111122.GB7663@breakpoint.cc> (raw)
In-Reply-To: <20171030145843.13496-1-sds@tycho.nsa.gov>

Stephen Smalley <sds@tycho.nsa.gov> wrote:
> Since 4.14-rc1, the selinux-testsuite has been encountering sporadic
> failures during testing of labeled IPSEC. git bisect pointed to
> commit ec30d78c14a813db39a647b6a348b4286 ("xfrm: add xdst pcpu cache").
> The xdst pcpu cache is only checking that the policies are the same,
> but does not validate that the policy, state, and flow match with respect
> to security context labeling.  As a result, the wrong SA could be used
> and the receiver could end up performing permission checking and
> providing SO_PEERSEC or SCM_SECURITY values for the wrong security context.
> security_xfrm_state_pol_flow_match() exists for this purpose and is
> already called from xfrm_state_look_at() for matching purposes.
> Further, xfrm_state_look_at() also performs a xfrm_selector_match() test,
> which is also missing from the xdst pcpu cache logic.  Add calls to both
> of these functions when validating the cache entry.  With these changes,
> the selinux-testsuite passes all tests again.
> 
> Fixes: ec30d78c14a813db39a647b6a348b4286ba4abf5 ("xfrm: add xdst pcpu cache")
> Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>
> ---
> This is an RFC because I am not entirely confident in the fix, e.g. is it
> sufficient to perform this matching only on the first xfrm or do they all
> need to be walked as in xfrm_bundle_ok()?  Also, should we perform this
> matching before (as in this patch) or after calling xfrm_bundle_ok()? Also,
> do we need to test xfrm->sel.family before calling xfrm_selector_match
> (as in this patch) or not - xfrm_state_look_at() does so when the
> state is XFRM_STATE_VALID but not when it is _ERROR or _EXPIRED?

No idea.

I looked at the old flow cache but i don't see any of these extra
checks there either.

However, old flow cache stored flowi struct as key, and that contains a
flowi_secid,  populated by the decode_session hooks.

Was it enough to check for identical flowi_secid in the flowi structs to
avoid this problem or am i missing something?
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  reply	other threads:[~2017-10-31 11:11 UTC|newest]

Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-10-30 14:58 [RFC PATCH] xfrm: fix regression introduced by xdst pcpu cache Stephen Smalley
2017-10-30 14:58 ` Stephen Smalley
2017-10-31 11:11 ` Florian Westphal [this message]
2017-10-31 11:11   ` Florian Westphal
     [not found]   ` <20171031111122.GB7663-E0PNVn5OA6ohrxcnuTQ+TQ@public.gmane.org>
2017-10-31 13:43     ` Stephen Smalley
2017-10-31 13:43       ` Stephen Smalley
2017-10-31 13:43       ` Stephen Smalley
2017-10-31 14:00       ` Stephen Smalley
2017-10-31 14:00         ` Stephen Smalley
2017-10-31 14:15       ` Florian Westphal
2017-10-31 14:15         ` Florian Westphal
2017-10-31 20:39 ` Paul Moore
2017-10-31 20:39   ` Paul Moore
2017-10-31 23:08   ` Florian Westphal
2017-10-31 23:08     ` Florian Westphal
2017-11-01 14:05     ` Stephen Smalley
2017-11-01 14:05       ` Stephen Smalley
2017-11-01 21:39     ` Paul Moore
2017-11-01 21:39       ` Paul Moore
2017-11-02 12:58       ` Stephen Smalley
2017-11-02 12:58         ` Stephen Smalley
2017-11-02 22:37         ` Paul Moore
2017-11-02 22:37           ` Paul Moore
  -- strict thread matches above, loose matches on Subject: below --
2017-10-27 15:28 Stephen Smalley
2017-10-27 15:28 ` Stephen Smalley

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