From fc18ffe58dc65fc0c5189d4bcdee1663dba30f26 Mon Sep 17 00:00:00 2001
From: Miciah Masters <miciah.masters@gmail.com>
Date: Mon, 22 May 2023 17:24:25 -0400
Subject: [PATCH] TopologyAwareHints: Take lock in HasPopulatedHints

Prevent potential concurrent map access by taking a lock before reading the
topology cache's hintsPopulatedByService map.

* staging/src/k8s.io/endpointslice/topologycache/topologycache.go
(setHintsLocked, hasPopulatedHintsLocked): New helper functions.  These are
the same as the existing SetHints and HasPopulatedHints methods except that
these helpers assume that a lock is already held.
(SetHints): Use setHintsLocked.
(HasPopulatedHints): Take a lock and use hasPopulatedHintsLocked.
(AddHints): Take a lock and use setHintsLocked and hasPopulatedHintsLocked.
* staging/src/k8s.io/endpointslice/topologycache/topologycache_test.go
(TestTopologyCacheRace): Add a goroutine that calls HasPopulatedHints.
---
 .../topologycache/topologycache.go              | 17 +++++++++++++++--
 .../topologycache/topologycache_test.go         |  3 +++
 2 files changed, 18 insertions(+), 2 deletions(-)

diff --git a/pkg/controller/endpointslice/topologycache/topologycache.go b/pkg/controller/endpointslice/topologycache/topologycache.go
index a8ba640942c..dadd3604581 100644
--- a/pkg/controller/endpointslice/topologycache/topologycache.go
+++ b/pkg/controller/endpointslice/topologycache/topologycache.go
@@ -154,8 +154,10 @@ func (t *TopologyCache) AddHints(si *SliceInfo) ([]*discovery.EndpointSlice, []*
 		return slicesToCreate, slicesToUpdate, events
 	}
 
-	hintsEnabled := t.hintsPopulatedByService.Has(si.ServiceKey)
-	t.SetHints(si.ServiceKey, si.AddressType, allocatedHintsByZone)
+	t.lock.Lock()
+	defer t.lock.Unlock()
+	hintsEnabled := t.hasPopulatedHintsLocked(si.ServiceKey)
+	t.setHintsLocked(si.ServiceKey, si.AddressType, allocatedHintsByZone)
 
 	// if hints were not enabled before, we publish an event to indicate we enabled them.
 	if !hintsEnabled {
@@ -175,6 +177,10 @@ func (t *TopologyCache) SetHints(serviceKey string, addrType discovery.AddressTy
 	t.lock.Lock()
 	defer t.lock.Unlock()
 
+	t.setHintsLocked(serviceKey, addrType, allocatedHintsByZone)
+}
+
+func (t *TopologyCache) setHintsLocked(serviceKey string, addrType discovery.AddressType, allocatedHintsByZone EndpointZoneInfo) {
 	_, ok := t.endpointsByService[serviceKey]
 	if !ok {
 		t.endpointsByService[serviceKey] = map[discovery.AddressType]EndpointZoneInfo{}
@@ -263,6 +269,13 @@ func (t *TopologyCache) SetNodes(nodes []*v1.Node) {
 
 // HasPopulatedHints checks whether there are populated hints for a given service in the cache.
 func (t *TopologyCache) HasPopulatedHints(serviceKey string) bool {
+	t.lock.Lock()
+	defer t.lock.Unlock()
+
+	return t.hasPopulatedHintsLocked(serviceKey)
+}
+
+func (t *TopologyCache) hasPopulatedHintsLocked(serviceKey string) bool {
 	return t.hintsPopulatedByService.Has(serviceKey)
 }
 
diff --git a/pkg/controller/endpointslice/topologycache/topologycache_test.go b/pkg/controller/endpointslice/topologycache/topologycache_test.go
index f4dbcce634f..664504b11a9 100644
--- a/pkg/controller/endpointslice/topologycache/topologycache_test.go
+++ b/pkg/controller/endpointslice/topologycache/topologycache_test.go
@@ -686,6 +686,9 @@ func TestTopologyCacheRace(t *testing.T) {
 	go func() {
 		cache.AddHints(sliceInfo)
 	}()
+	go func() {
+		cache.HasPopulatedHints(sliceInfo.ServiceKey)
+	}()
 }
 
 // Test Helpers