sessionctx: add time zone check (#9822)

sessionctx/variable/varsutil.go

@@ -489,9 +489,20 @@ func parseTimeZone(s string) (*time.Location, error) {
 	}
 
 	// The value can be given as a string indicating an offset from UTC, such as '+10:00' or '-6:00'.
+	// The time zone's value should in [-12:59,+14:00].
 	if strings.HasPrefix(s, "+") || strings.HasPrefix(s, "-") {
 		d, err := types.ParseDuration(nil, s[1:], 0)
 		if err == nil {
+			if s[0] == '-' {
+				if d.Duration > 12*time.Hour+59*time.Minute {
+					return nil, ErrUnknownTimeZone.GenWithStackByArgs(s)
+				}
+			} else {
+				if d.Duration > 14*time.Hour {
+					return nil, ErrUnknownTimeZone.GenWithStackByArgs(s)
+				}
+			}
+
 			ofst := int(d.Duration / time.Second)
 			if s[0] == '-' {
 				ofst = -ofst

sessionctx/variable/varsutil_test.go

@@ -143,16 +143,26 @@ func (s *testVarsutilSuite) TestVarsutil(c *C) {
 		expect       string
 		compareValue bool
 		diff         time.Duration
+		err          error
 	}{
-		{"Europe/Helsinki", "Europe/Helsinki", true, -2 * time.Hour},
-		{"US/Eastern", "US/Eastern", true, 5 * time.Hour},
+		{"Europe/Helsinki", "Europe/Helsinki", true, -2 * time.Hour, nil},
+		{"US/Eastern", "US/Eastern", true, 5 * time.Hour, nil},
 		//TODO: Check it out and reopen this case.
 		//{"SYSTEM", "Local", false, 0},
-		{"+10:00", "", true, -10 * time.Hour},
-		{"-6:00", "", true, 6 * time.Hour},
+		{"+10:00", "", true, -10 * time.Hour, nil},
+		{"-6:00", "", true, 6 * time.Hour, nil},
+		{"+14:00", "", true, -14 * time.Hour, nil},
+		{"-12:59", "", true, 12*time.Hour + 59*time.Minute, nil},
+		{"+14:01", "", false, -14 * time.Hour, ErrUnknownTimeZone.GenWithStackByArgs("+14:01")},
+		{"-13:00", "", false, 13 * time.Hour, ErrUnknownTimeZone.GenWithStackByArgs("-13:00")},
 	}
 	for _, tt := range tests {
 		err = SetSessionSystemVar(v, TimeZone, types.NewStringDatum(tt.input))
+		if tt.err != nil {
+			c.Assert(err, NotNil)
+			continue
+		}
+
 		c.Assert(err, IsNil)
 		c.Assert(v.TimeZone.String(), Equals, tt.expect)
 		if tt.compareValue {