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fix TOCTOU race BM25 cache version check

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This commit is contained in:
afjcjsbx 2026-03-08 16:12:21 +01:00
parent 86cb4f008a
commit 93ff2aca84
1 changed files with 15 additions and 7 deletions
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22
pkg/tools/search_tool.go
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@ -217,16 +217,19 @@ type bm25CachedEngine struct {
// getOrBuildEngine returns a cached BM25 engine, rebuilding it only when // getOrBuildEngine returns a cached BM25 engine, rebuilding it only when
// the registry version has changed (new tools registered). // the registry version has changed (new tools registered).
func (t *BM25SearchTool) getOrBuildEngine() *bm25CachedEngine { func (t *BM25SearchTool) getOrBuildEngine() *bm25CachedEngine {
currentVersion := t.registry.version.Load() // Fast path: optimistic check without locking the registry.
// If the version hasn't changed, the cache is still valid.
if t.cachedEngine != nil && t.cacheVersion == t.registry.version.Load() {
return t.cachedEngine
}
t.cacheMu.Lock() t.cacheMu.Lock()
defer t.cacheMu.Unlock() defer t.cacheMu.Unlock()
if t.cachedEngine != nil && t.cacheVersion == currentVersion { // Read version inside the registry RLock so the snapshot and version
return t.cachedEngine // are guaranteed to be consistent (no TOCTOU between Load and RLock).
}
t.registry.mu.RLock() t.registry.mu.RLock()
snapshotVersion := t.registry.version.Load()
snapshot := make([]searchDoc, 0, len(t.registry.tools)) snapshot := make([]searchDoc, 0, len(t.registry.tools))
for name, entry := range t.registry.tools { for name, entry := range t.registry.tools {
if !entry.IsCore { if !entry.IsCore {
@ -238,9 +241,14 @@ func (t *BM25SearchTool) getOrBuildEngine() *bm25CachedEngine {
} }
t.registry.mu.RUnlock() t.registry.mu.RUnlock()
// Re-check: another goroutine may have rebuilt while we waited for cacheMu.
if t.cachedEngine != nil && t.cacheVersion == snapshotVersion {
return t.cachedEngine
}
if len(snapshot) == 0 { if len(snapshot) == 0 {
t.cachedEngine = nil t.cachedEngine = nil
t.cacheVersion = currentVersion t.cacheVersion = snapshotVersion
return nil return nil
} }
@ -253,7 +261,7 @@ func (t *BM25SearchTool) getOrBuildEngine() *bm25CachedEngine {
cached := &bm25CachedEngine{engine: engine} cached := &bm25CachedEngine{engine: engine}
t.cachedEngine = cached t.cachedEngine = cached
t.cacheVersion = currentVersion t.cacheVersion = snapshotVersion
return cached return cached
} }