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Fix potential race in dispatching watch event

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This commit is contained in:
Wojciech Tyczyński 2022-02-22 17:14:15 +01:00
parent 0cb3a02bbe
commit 779f157ecf
3 changed files with 17 additions and 20 deletions
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20
staging/src/k8s.io/apiserver/pkg/storage/cacher/cacher.go
View File

@ -851,14 +851,14 @@ func (c *Cacher) dispatchEvent(event *watchCacheEvent) {
// from it justifies increased memory usage, so for now we drop the cached
// serializations after dispatching this event.
//
// Given the deep-copies that are done to create cachingObjects,
// we try to cache serializations only if there are at least 3 watchers.
if len(c.watchersBuffer) >= 3 {
// Make a shallow copy to allow overwriting Object and PrevObject.
wcEvent := *event
setCachingObjects(&wcEvent, c.versioner)
event = &wcEvent
}
// Given that CachingObject is just wrapping the object and not perfoming
// deep-copying (until some field is explicitly being modified), we create
// it unconditionally to ensure safety and reduce deep-copying.
//
// Make a shallow copy to allow overwriting Object and PrevObject.
wcEvent := *event
setCachingObjects(&wcEvent, c.versioner)
event = &wcEvent
c.blockedWatchers = c.blockedWatchers[:0]
for _, watcher := range c.watchersBuffer {
@ -1288,9 +1288,9 @@ func (c *cacheWatcher) convertToWatchEvent(event *watchCacheEvent) *watch.Event
switch {
case curObjPasses && !oldObjPasses:
return &watch.Event{Type: watch.Added, Object: event.Object}
return &watch.Event{Type: watch.Added, Object: getMutableObject(event.Object)}
case curObjPasses && oldObjPasses:
return &watch.Event{Type: watch.Modified, Object: event.Object}
return &watch.Event{Type: watch.Modified, Object: getMutableObject(event.Object)}
case !curObjPasses && oldObjPasses:
// return a delete event with the previous object content, but with the event's resource version
oldObj := getMutableObject(event.PrevObject)

13
staging/src/k8s.io/apiserver/pkg/storage/cacher/cacher_whitebox_test.go
View File

@ -1370,17 +1370,10 @@ func testCachingObjects(t *testing.T, watchersCount int) {
}
var object runtime.Object
if watchersCount >= 3 {
if _, ok := event.Object.(runtime.CacheableObject); !ok {
t.Fatalf("Object in %s event should support caching: %#v", event.Type, event.Object)
}
object = event.Object.(runtime.CacheableObject).GetObject()
} else {
if _, ok := event.Object.(runtime.CacheableObject); ok {
t.Fatalf("Object in %s event should not support caching: %#v", event.Type, event.Object)
}
object = event.Object.DeepCopyObject()
if _, ok := event.Object.(runtime.CacheableObject); !ok {
t.Fatalf("Object in %s event should support caching: %#v", event.Type, event.Object)
}
object = event.Object.(runtime.CacheableObject).GetObject()
if event.Type == watch.Deleted {
resourceVersion, err := cacher.versioner.ObjectResourceVersion(cacher.watchCache.cache[index].PrevObject)

4
staging/src/k8s.io/apiserver/pkg/storage/cacher/caching_object.go
View File

@ -137,6 +137,10 @@ func (o *cachingObject) CacheEncode(id runtime.Identifier, encode func(runtime.O
result := o.getSerializationResult(id)
result.once.Do(func() {
buffer := bytes.NewBuffer(nil)
// TODO(wojtek-t): This is currently making a copy to avoid races
// in cases where encoding is making subtle object modifications,
// e.g. #82497
// Figure out if we can somehow avoid this under some conditions.
result.err = encode(o.GetObject(), buffer)
result.raw = buffer.Bytes()
})