db: check bounds on level number in options

Author: RaduBerinde

options.go

@@ -2274,11 +2274,13 @@ func (o *Options) Parse(s string, hooks *ParseHooks) error {
 			if m == nil {
 				return errors.Errorf("pebble: unknown section: %q", errors.Safe(section))
 			}
-			index, _ := strconv.Atoi(m[1])
+			index, err := strconv.Atoi(m[1])
+			if err != nil || index < 0 || index >= len(o.Levels) {
+				return errors.Errorf("pebble: invalid level index: %q", errors.Safe(m[1]))
+			}
 
 			l := &o.Levels[index]
 
-			var err error
 			switch key {
 			case "block_restart_interval":
 				l.BlockRestartInterval, err = strconv.Atoi(value)

options_test.go

@@ -461,6 +461,36 @@ func TestOptionsParseLevelNoQuotes(t *testing.T) {
 	require.Equal(t, o1.String(), o2.String())
 }
 
+func TestOptionsParseInvalidLevel(t *testing.T) {
+	str := `
+[Options]
+[Level 1]
+  block_restart_interval=8
+  block_size=10
+[Level 10]
+  block_restart_interval=8
+  block_size=10
+`
+	o := &Options{}
+	require.Error(t, o.Parse(str, nil))
+
+	str = `
+[Options]
+[Level -1]
+  block_restart_interval=8
+  block_size=10
+`
+	require.Error(t, o.Parse(str, nil))
+
+	str = `
+[Options]
+[Level 100000000000000000000000000]
+  block_restart_interval=8
+  block_size=10
+`
+	require.Error(t, o.Parse(str, nil))
+}
+
 func TestOptionsParseComparerOverwrite(t *testing.T) {
 	// Test that an unrecognized comparer in the OPTIONS file does not nil out
 	// the Comparer field.