From cab4d09ead9ad6914e0dc61f6dd3b02ea5c1cdff Mon Sep 17 00:00:00 2001
From: bb7133 <bb7133@gmail.com>
Date: Sun, 21 Aug 2022 17:26:10 +0800
Subject: [PATCH] sessionctx/variable: fix range check for @@timestamp

---
 sessionctx/variable/sysvar.go      |  8 +++++++-
 sessionctx/variable/sysvar_test.go | 18 ++++++++++++++++++
 sessionctx/variable/tidb_vars.go   |  1 +
 3 files changed, 26 insertions(+), 1 deletion(-)

diff --git a/sessionctx/variable/sysvar.go b/sessionctx/variable/sysvar.go
index 8979518a8d6a5..5abfc54ac26b8 100644
--- a/sessionctx/variable/sysvar.go
+++ b/sessionctx/variable/sysvar.go
@@ -77,7 +77,7 @@ var defaultSysVars = []*SysVar{
 	{Scope: ScopeNone, Name: TiDBAllowFunctionForExpressionIndex, ReadOnly: true, Value: collectAllowFuncName4ExpressionIndex()},
 
 	/* The system variables below have SESSION scope  */
-	{Scope: ScopeSession, Name: Timestamp, Value: DefTimestamp, MinValue: 0, MaxValue: 2147483647, Type: TypeFloat, GetSession: func(s *SessionVars) (string, error) {
+	{Scope: ScopeSession, Name: Timestamp, Value: DefTimestamp, MinValue: 0, MaxValue: math.MaxInt32, Type: TypeFloat, GetSession: func(s *SessionVars) (string, error) {
 		if timestamp, ok := s.systems[Timestamp]; ok && timestamp != DefTimestamp {
 			return timestamp, nil
 		}
@@ -86,6 +86,12 @@ var defaultSysVars = []*SysVar{
 	}, GetStateValue: func(s *SessionVars) (string, bool, error) {
 		timestamp, ok := s.systems[Timestamp]
 		return timestamp, ok && timestamp != DefTimestamp, nil
+	}, Validation: func(vars *SessionVars, normalizedValue string, originalValue string, scope ScopeFlag) (string, error) {
+		val := tidbOptFloat64(originalValue, DefTimestampFloat)
+		if val > math.MaxInt32 {
+			return originalValue, ErrWrongValueForVar.GenWithStackByArgs(Timestamp, originalValue)
+		}
+		return normalizedValue, nil
 	}},
 	{Scope: ScopeSession, Name: WarningCount, Value: "0", ReadOnly: true, GetSession: func(s *SessionVars) (string, error) {
 		return strconv.Itoa(s.SysWarningCount), nil
diff --git a/sessionctx/variable/sysvar_test.go b/sessionctx/variable/sysvar_test.go
index 0467dbba9f620..28a0315fb93f6 100644
--- a/sessionctx/variable/sysvar_test.go
+++ b/sessionctx/variable/sysvar_test.go
@@ -821,6 +821,24 @@ func TestTimestamp(t *testing.T) {
 	require.NoError(t, err)
 	require.NotEqual(t, "", val)
 	require.NotEqual(t, "10", val)
+
+	// Test validating a value that less than the minimum one.
+	sv := GetSysVar(Timestamp)
+	_, err = sv.Validate(vars, "-5", ScopeSession)
+	require.NoError(t, err)
+	warn := vars.StmtCtx.GetWarnings()[0].Err
+	require.Equal(t, "[variable:1292]Truncated incorrect timestamp value: '-5'", warn.Error())
+
+	// Test validating values that larger than the maximum one.
+	_, err = sv.Validate(vars, "3147483698", ScopeSession)
+	require.Equal(t, "[variable:1231]Variable 'timestamp' can't be set to the value of '3147483698'", err.Error())
+
+	_, err = sv.Validate(vars, "2147483648", ScopeSession)
+	require.Equal(t, "[variable:1231]Variable 'timestamp' can't be set to the value of '2147483648'", err.Error())
+
+	// Test validating the maximum value.
+	_, err = sv.Validate(vars, "2147483647", ScopeSession)
+	require.NoError(t, err)
 }
 
 func TestIdentity(t *testing.T) {
diff --git a/sessionctx/variable/tidb_vars.go b/sessionctx/variable/tidb_vars.go
index e1bae81b229d5..2520b669e22e1 100644
--- a/sessionctx/variable/tidb_vars.go
+++ b/sessionctx/variable/tidb_vars.go
@@ -958,6 +958,7 @@ const (
 	DefTiDBRegardNULLAsPoint                       = true
 	DefEnablePlacementCheck                        = true
 	DefTimestamp                                   = "0"
+	DefTimestampFloat                              = 0.0
 	DefTiDBEnableStmtSummary                       = true
 	DefTiDBStmtSummaryInternalQuery                = false
 	DefTiDBStmtSummaryRefreshInterval              = 1800