linux-kernel - [PATCH AUTOSEL for 4.9 34/49] xfrm: Fix stack-out-of-bounds read on socket policy lookup.

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Date:   Sun, 28 Jan 2018 22:27:58 +0000
From:   Sasha Levin <Alexander.Levin@...rosoft.com>
To:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>
CC:     Steffen Klassert <steffen.klassert@...unet.com>,
        Sasha Levin <Alexander.Levin@...rosoft.com>
Subject: [PATCH AUTOSEL for 4.9 34/49] xfrm: Fix stack-out-of-bounds read on
 socket policy lookup.

From: Steffen Klassert <steffen.klassert@...unet.com>

[ Upstream commit ddc47e4404b58f03e98345398fb12d38fe291512 ]

When we do tunnel or beet mode, we pass saddr and daddr from the
template to xfrm_state_find(), this is ok. On transport mode,
we pass the addresses from the flowi, assuming that the IP
addresses (and address family) don't change during transformation.
This assumption is wrong in the IPv4 mapped IPv6 case, packet
is IPv4 and template is IPv6.

Fix this by catching address family missmatches of the policy
and the flow already before we do the lookup.

Reported-by: syzbot <syzkaller@...glegroups.com>
Signed-off-by: Steffen Klassert <steffen.klassert@...unet.com>
Signed-off-by: Sasha Levin <alexander.levin@...rosoft.com>
---
 net/xfrm/xfrm_policy.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/net/xfrm/xfrm_policy.c b/net/xfrm/xfrm_policy.c
index f19e6a57e118..cfe13a4385c1 100644
--- a/net/xfrm/xfrm_policy.c
+++ b/net/xfrm/xfrm_policy.c
@@ -1256,9 +1256,15 @@ static struct xfrm_policy *xfrm_sk_policy_lookup(const struct sock *sk, int dir,
  again:
 	pol = rcu_dereference(sk->sk_policy[dir]);
 	if (pol != NULL) {
-		bool match = xfrm_selector_match(&pol->selector, fl, family);
+		bool match;
 		int err = 0;
 
+		if (pol->family != family) {
+			pol = NULL;
+			goto out;
+		}
+
+		match = xfrm_selector_match(&pol->selector, fl, family);
 		if (match) {
 			if ((sk->sk_mark & pol->mark.m) != pol->mark.v) {
 				pol = NULL;
-- 
2.11.0