xfrm: Fix wraparound in xfrm_policy_addr_delta()

Use three-way comparison for address components to avoid integer
wraparound in the result of xfrm_policy_addr_delta(). This ensures
that the search trees are built and traversed correctly.

Treat IPv4 and IPv6 similarly by returning 0 when prefixlen == 0.
Prefix /0 has only one equivalence class.

Fixes: 9cf545ebd591d ("xfrm: policy: store inexact policies in a tree ordered by destination address")
Signed-off-by: Visa Hankala <[e-mail]>
Acked-by: Florian Westphal <[e-mail]>
Signed-off-by: Steffen Klassert <[e-mail]>

net/xfrm/xfrm_policy.c

···
 				  const xfrm_address_t *b,
 				  u8 prefixlen, u16 family)
 {
+	u32 ma, mb, mask;
 	unsigned int pdw, pbi;
 	int delta = 0;
 
 	switch (family) {
 	case AF_INET:
-		if (sizeof(long) == 4 && prefixlen == 0)
-			return ntohl(a->a4) - ntohl(b->a4);
-		return (ntohl(a->a4) & ((~0UL << (32 - prefixlen)))) -
-		       (ntohl(b->a4) & ((~0UL << (32 - prefixlen))));
+		if (prefixlen == 0)
+			return 0;
+		mask = ~0U << (32 - prefixlen);
+		ma = ntohl(a->a4) & mask;
+		mb = ntohl(b->a4) & mask;
+		if (ma < mb)
+			delta = -1;
+		else if (ma > mb)
+			delta = 1;
+		break;
 	case AF_INET6:
 		pdw = prefixlen >> 5;
 		pbi = prefixlen & 0x1f;
···
 				return delta;
 		}
 		if (pbi) {
-			u32 mask = ~0u << (32 - pbi);
-
-			delta = (ntohl(a->a6[pdw]) & mask) -
-				(ntohl(b->a6[pdw]) & mask);
+			mask = ~0U << (32 - pbi);
+			ma = ntohl(a->a6[pdw]) & mask;
+			mb = ntohl(b->a6[pdw]) & mask;
+			if (ma < mb)
+				delta = -1;
+			else if (ma > mb)
+				delta = 1;
 		}
 		break;
 	default:

tools/testing/selftests/net/xfrm_policy.sh

···
 	return 0
 }
 
+# insert non-overlapping policies in a random order and check that
+# all of them can be fetched using the traffic selectors.
+check_random_order()
+{
+	local ns=$1
+	local log=$2
+
+	for i in $(seq 100); do
+		ip -net $ns xfrm policy flush
+		for j in $(seq 0 16 255 | sort -R); do
+			ip -net $ns xfrm policy add dst $j.0.0.0/24 dir out priority 10 action allow
+		done
+		for j in $(seq 0 16 255); do
+			if ! ip -net $ns xfrm policy get dst $j.0.0.0/24 dir out > /dev/null; then
+				echo "FAIL: $log" 1>&2
+				return 1
+			fi
+		done
+	done
+
+	for i in $(seq 100); do
+		ip -net $ns xfrm policy flush
+		for j in $(seq 0 16 255 | sort -R); do
+			local addr=$(printf "e000:0000:%02x00::/56" $j)
+			ip -net $ns xfrm policy add dst $addr dir out priority 10 action allow
+		done
+		for j in $(seq 0 16 255); do
+			local addr=$(printf "e000:0000:%02x00::/56" $j)
+			if ! ip -net $ns xfrm policy get dst $addr dir out > /dev/null; then
+				echo "FAIL: $log" 1>&2
+				return 1
+			fi
+		done
+	done
+
+	ip -net $ns xfrm policy flush
+
+	echo "PASS: $log"
+	return 0
+}
+
 #check for needed privileges
 if [ "$(id -u)" -ne 0 ];then
 	echo "SKIP: Need root privileges"
···
 check_exceptions "exceptions and block policies after htresh change to normal"
 
 check_hthresh_repeat "policies with repeated htresh change"
+
+check_random_order ns3 "policies inserted in random order"
 
 for i in 1 2 3 4;do ip netns del ns$i;done