Add missing check for nil expression

promql/parse.go

@@ -464,9 +464,6 @@ func (p *parser) recordStmt() *RecordStmt {
 func (p *parser) expr() Expr {
 	// Parse the starting expression.
 	expr := p.unaryExpr()
-	if expr == nil {
-		p.errorf("no valid expression found")
-	}
 
 	// Loop through the operations and construct a binary operation tree based
 	// on the operators' precedence.
@@ -514,9 +511,6 @@ func (p *parser) expr() Expr {
 
 		// Parse the next operand.
 		rhs := p.unaryExpr()
-		if rhs == nil {
-			p.errorf("missing right-hand side in binary expression")
-		}
 
 		// Assign the new root based on the precendence of the LHS and RHS operators.
 		if lhs, ok := expr.(*BinaryExpr); ok && lhs.Op.precedence() < op.precedence() {
@@ -552,6 +546,7 @@ func (p *parser) unaryExpr() Expr {
 	case itemADD, itemSUB:
 		p.next()
 		e := p.unaryExpr()
+
 		// Simplify unary expressions for number literals.
 		if nl, ok := e.(*NumberLiteral); ok {
 			if t.typ == itemSUB {
@@ -665,6 +660,9 @@ func (p *parser) primaryExpr() Expr {
 	case t.typ.isAggregator():
 		p.backup()
 		return p.aggrExpr()
+
+	default:
+		p.errorf("no valid expression found")
 	}
 	return nil
 }

promql/parse_test.go

@@ -134,7 +134,7 @@ var testExpr = []struct {
 	}, {
 		input:  "1+",
 		fail:   true,
-		errMsg: "missing right-hand side in binary expression",
+		errMsg: "no valid expression found",
 	}, {
 		input:  ".",
 		fail:   true,
@@ -154,7 +154,7 @@ var testExpr = []struct {
 	}, {
 		input:  "1 /",
 		fail:   true,
-		errMsg: "missing right-hand side in binary expression",
+		errMsg: "no valid expression found",
 	}, {
 		input:  "*1",
 		fail:   true,
@@ -945,6 +945,27 @@ var testExpr = []struct {
 		fail:   true,
 		errMsg: "expected type matrix in call to function \"rate\", got vector",
 	},
+	// Fuzzing regression tests.
+	{
+		input:  "-=",
+		fail:   true,
+		errMsg: `no valid expression found`,
+	},
+	{
+		input:  "++-++-+-+-<",
+		fail:   true,
+		errMsg: `no valid expression found`,
+	},
+	{
+		input:  "e-+=/(0)",
+		fail:   true,
+		errMsg: `no valid expression found`,
+	},
+	{
+		input:  "-If",
+		fail:   true,
+		errMsg: `no valid expression found`,
+	},
 }
 
 func TestParseExpressions(t *testing.T) {