fix: Change kernel config detection failure to info level

Tetragon attempts to read the kernel config by trying a couple of places
where it is found. This should be Info instead of Error.
detectAuditLoginuid() function was removed and its logic was implemented into
detectAuditLoginuidOnce(). Testing was done by mocking getKernelConfig() function,
returning error and validating that the new log is of Info level:

getKernelConfigMock = sync.OnceValue(func() error { return errors.New("Mocked getKernelConfig function for testing") })

Testing Results:
when the function works no log is shown and loginuid is enabled
when mocking the function a log with undetected loginuid file is shown

Signed-off-by: Daniel Gomez <[email protected]>

Author: dangome3

pkg/bpf/detect_linux.go

@@ -524,20 +524,23 @@ func HasUprobeRefCtrOffset() bool {
 	return uprobeRefCtrOffset.detected
 }
 
-func detectAuditLoginuid() bool {
-	if kernels.MinKernelVersion("5.1") && kernels.DetectConfig(kernels.CONFIG_AUDIT) {
-		return true
-	} else if kernels.DetectConfig(kernels.CONFIG_AUDITSYSCALL) {
-		return true
-	}
-
-	_, err := os.Stat("/proc/self/loginuid")
-	return err == nil
-}
-
 func detectAuditLoginuidOnce() {
 	auditLoginuid.init.Do(func() {
-		auditLoginuid.detected = detectAuditLoginuid()
+		cfg := kernels.CONFIG_AUDITSYSCALL
+		if kernels.MinKernelVersion("5.1") {
+			cfg = kernels.CONFIG_AUDIT
+		}
+		if ok, errConfig := kernels.DetectConfig(cfg); ok {
+			auditLoginuid.detected = true
+		} else if _, errStat := os.Stat("/proc/self/loginuid"); errStat == nil {
+			auditLoginuid.detected = true
+		} else {
+			if errConfig != nil {
+				logger.GetLogger().Info("failed to detect config and to stat loginuid", "config_error", errConfig, "config", string(cfg), "stat_error", errStat)
+			} else {
+				logger.GetLogger().Info("failed to stat loginuid", logfields.Error, errStat)
+			}
+		}
 	})
 }
 

pkg/kernels/config.go

@@ -131,22 +131,21 @@ func initKernelConfig() error {
 
 // DetectConfig checks if a kernel config option is enabled
 // It first tries /proc/config.gz, then looks for config file in /boot for the current kernel
-func DetectConfig(conf Config) bool {
+func DetectConfig(conf Config) (bool, error) {
 	if err := getKernelConfig(); err != nil {
-		logger.GetLogger().Error("Detecting kernel config failed", logfields.Error, err)
-		return false
+		return false, fmt.Errorf("getting kernel config failed: %w", err)
 	}
 
 	if val, ok := kernelConfigMap[conf]; ok {
 		// Only check for CONFIG_XXX=y or CONFIG_XXX=m. When the value is a string or number,
 		// it's mostly treated as a kernel parameter rather than a feature switch,
 		// so we temporarily filter these out.
 		if val == "y" || val == "m" {
-			return true
+			return true, nil
 		}
 	}
 
-	return false
+	return false, nil
 }
 
 func LogConfigs() string {