Fix division by zero (#71)

* Fix division by zero in cgroups

* Fix division by zero in cgroups2

* Add test data for zero period cgroups

* Add test data for zero period cgroups quota

* Add test data for zero period cgroups2

* Add cgroups test

* Add cgroups2 zero period test

internal/cgroups/cgroups.go

@@ -110,8 +110,8 @@ func (cg CGroups) CPUQuota() (float64, bool, error) {
 	}
 
 	cfsPeriodUs, err := cpuCGroup.readInt(_cgroupCPUCFSPeriodUsParam)
-	if err != nil {
-		return -1, false, err
+	if defined := cfsPeriodUs > 0; err != nil || !defined {
+		return -1, defined, err
 	}
 
 	return float64(cfsQuotaUs) / float64(cfsPeriodUs), true, nil

internal/cgroups/cgroups2.go

@@ -159,6 +159,10 @@ func (cg *CGroups2) CPUQuota() (float64, bool, error) {
 			if err != nil {
 				return -1, false, err
 			}
+
+			if period == 0 {
+				return -1, false, errors.New("zero value for period is not allowed")
+			}
 		}
 
 		return float64(max) / float64(period), true, nil

internal/cgroups/cgroups2_test.go

@@ -125,6 +125,10 @@ func TestCGroupsCPUQuotaV2(t *testing.T) {
 			name:    "too-many-fields",
 			wantErr: "invalid format",
 		},
+		{
+			name:    "zero-period",
+			wantErr: "zero value for period is not allowed",
+		},
 	}
 
 	mountPoint := filepath.Join(testDataCGroupsPath, "v2")

internal/cgroups/cgroups_test.go

@@ -102,6 +102,12 @@ func TestCGroupsCPUQuota(t *testing.T) {
 			expectedDefined: false,
 			shouldHaveError: false,
 		},
+		{
+			name:            "zero-period",
+			expectedQuota:   -1.0,
+			expectedDefined: false,
+			shouldHaveError: false,
+		},
 		{
 			name:            "undefined-period",
 			expectedQuota:   -1.0,

internal/cgroups/testdata/cgroups/v2/zero-period

@@ -0,0 +1 @@
+250000 0

internal/cgroups/testdata/cgroups/zero-period/cpu.cfs_period_us

@@ -0,0 +1 @@
+0

internal/cgroups/testdata/cgroups/zero-period/cpu.cfs_quota_us

@@ -0,0 +1 @@
+600000