linux-kernel - [PATCH 5.8 064/124] xfrm: Use correct address family in xfrm_state

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Date:   Mon, 12 Oct 2020 15:31:08 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        syzbot+577fbac3145a6eb2e7a5@...kaller.appspotmail.com,
        Herbert Xu <herbert@...dor.apana.org.au>,
        Steffen Klassert <steffen.klassert@...unet.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.8 064/124] xfrm: Use correct address family in xfrm_state_find

From: Herbert Xu <herbert@...dor.apana.org.au>

[ Upstream commit e94ee171349db84c7cfdc5fefbebe414054d0924 ]

The struct flowi must never be interpreted by itself as its size
depends on the address family.  Therefore it must always be grouped
with its original family value.

In this particular instance, the original family value is lost in
the function xfrm_state_find.  Therefore we get a bogus read when
it's coupled with the wrong family which would occur with inter-
family xfrm states.

This patch fixes it by keeping the original family value.

Note that the same bug could potentially occur in LSM through
the xfrm_state_pol_flow_match hook.  I checked the current code
there and it seems to be safe for now as only secid is used which
is part of struct flowi_common.  But that API should be changed
so that so that we don't get new bugs in the future.  We could
do that by replacing fl with just secid or adding a family field.

Reported-by: syzbot+577fbac3145a6eb2e7a5@...kaller.appspotmail.com
Fixes: 48b8d78315bf ("[XFRM]: State selection update to use inner...")
Signed-off-by: Herbert Xu <herbert@...dor.apana.org.au>
Signed-off-by: Steffen Klassert <steffen.klassert@...unet.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 net/xfrm/xfrm_state.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/net/xfrm/xfrm_state.c b/net/xfrm/xfrm_state.c
index 6b431a3830721..158510cd34ae8 100644
--- a/net/xfrm/xfrm_state.c
+++ b/net/xfrm/xfrm_state.c
@@ -1019,7 +1019,8 @@ static void xfrm_state_look_at(struct xfrm_policy *pol, struct xfrm_state *x,
 	 */
 	if (x->km.state == XFRM_STATE_VALID) {
 		if ((x->sel.family &&
-		     !xfrm_selector_match(&x->sel, fl, x->sel.family)) ||
+		     (x->sel.family != family ||
+		      !xfrm_selector_match(&x->sel, fl, family))) ||
 		    !security_xfrm_state_pol_flow_match(x, pol, fl))
 			return;
 
@@ -1032,7 +1033,9 @@ static void xfrm_state_look_at(struct xfrm_policy *pol, struct xfrm_state *x,
 		*acq_in_progress = 1;
 	} else if (x->km.state == XFRM_STATE_ERROR ||
 		   x->km.state == XFRM_STATE_EXPIRED) {
-		if (xfrm_selector_match(&x->sel, fl, x->sel.family) &&
+		if ((!x->sel.family ||
+		     (x->sel.family == family &&
+		      xfrm_selector_match(&x->sel, fl, family))) &&
 		    security_xfrm_state_pol_flow_match(x, pol, fl))
 			*error = -ESRCH;
 	}
@@ -1072,7 +1075,7 @@ xfrm_state_find(const xfrm_address_t *daddr, const xfrm_address_t *saddr,
 		    tmpl->mode == x->props.mode &&
 		    tmpl->id.proto == x->id.proto &&
 		    (tmpl->id.spi == x->id.spi || !tmpl->id.spi))
-			xfrm_state_look_at(pol, x, fl, encap_family,
+			xfrm_state_look_at(pol, x, fl, family,
 					   &best, &acquire_in_progress, &error);
 	}
 	if (best || acquire_in_progress)
@@ -1089,7 +1092,7 @@ xfrm_state_find(const xfrm_address_t *daddr, const xfrm_address_t *saddr,
 		    tmpl->mode == x->props.mode &&
 		    tmpl->id.proto == x->id.proto &&
 		    (tmpl->id.spi == x->id.spi || !tmpl->id.spi))
-			xfrm_state_look_at(pol, x, fl, encap_family,
+			xfrm_state_look_at(pol, x, fl, family,
 					   &best, &acquire_in_progress, &error);
 	}
 
-- 
2.25.1