xfrm: Fix wraparound in xfrm_policy_addr_delta()

[ Upstream commit da64ae2d35d3673233f0403b035d4c6acbf71965 ]

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: 9cf545ebd5 ("xfrm: policy: store inexact policies in a tree ordered by destination address")
Signed-off-by: Visa Hankala <visa@hankala.org>
Acked-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

tools/testing/selftests/net/xfrm_policy.sh

@@ -287,6 +287,47 @@ check_hthresh_repeat()
 	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"
@@ -438,6 +479,8 @@ 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
 
 exit $ret