1 files changed, 19 insertions, 12 deletions

diff --git a/libgo/go/encoding/json/scanner.go b/libgo/go/encoding/json/scanner.go
index 552bd70..9dc1903 100644
--- a/libgo/go/encoding/json/scanner.go
+++ b/libgo/go/encoding/json/scanner.go
@@ -139,6 +139,10 @@ const (
 	parseArrayValue         // parsing array value
 )
 
+// This limits the max nesting depth to prevent stack overflow.
+// This is permitted by https://tools.ietf.org/html/rfc7159#section-9
+const maxNestingDepth = 10000
+
 // reset prepares the scanner for use.
 // It must be called before calling s.step.
 func (s *scanner) reset() {
@@ -168,8 +172,13 @@ func (s *scanner) eof() int {
 }
 
 // pushParseState pushes a new parse state p onto the parse stack.
-func (s *scanner) pushParseState(p int) {
-	s.parseState = append(s.parseState, p)
+// an error state is returned if maxNestingDepth was exceeded, otherwise successState is returned.
+func (s *scanner) pushParseState(c byte, newParseState int, successState int) int {
+	s.parseState = append(s.parseState, newParseState)
+	if len(s.parseState) <= maxNestingDepth {
+		return successState
+	}
+	return s.error(c, "exceeded max depth")
 }
 
 // popParseState pops a parse state (already obtained) off the stack
@@ -186,12 +195,12 @@ func (s *scanner) popParseState() {
 }
 
 func isSpace(c byte) bool {
-	return c == ' ' || c == '\t' || c == '\r' || c == '\n'
+	return c <= ' ' && (c == ' ' || c == '\t' || c == '\r' || c == '\n')
 }
 
 // stateBeginValueOrEmpty is the state after reading `[`.
 func stateBeginValueOrEmpty(s *scanner, c byte) int {
-	if c <= ' ' && isSpace(c) {
+	if isSpace(c) {
 		return scanSkipSpace
 	}
 	if c == ']' {
@@ -202,18 +211,16 @@ func stateBeginValueOrEmpty(s *scanner, c byte) int {
 
 // stateBeginValue is the state at the beginning of the input.
 func stateBeginValue(s *scanner, c byte) int {
-	if c <= ' ' && isSpace(c) {
+	if isSpace(c) {
 		return scanSkipSpace
 	}
 	switch c {
 	case '{':
 		s.step = stateBeginStringOrEmpty
-		s.pushParseState(parseObjectKey)
-		return scanBeginObject
+		return s.pushParseState(c, parseObjectKey, scanBeginObject)
 	case '[':
 		s.step = stateBeginValueOrEmpty
-		s.pushParseState(parseArrayValue)
-		return scanBeginArray
+		return s.pushParseState(c, parseArrayValue, scanBeginArray)
 	case '"':
 		s.step = stateInString
 		return scanBeginLiteral
@@ -242,7 +249,7 @@ func stateBeginValue(s *scanner, c byte) int {
 
 // stateBeginStringOrEmpty is the state after reading `{`.
 func stateBeginStringOrEmpty(s *scanner, c byte) int {
-	if c <= ' ' && isSpace(c) {
+	if isSpace(c) {
 		return scanSkipSpace
 	}
 	if c == '}' {
@@ -255,7 +262,7 @@ func stateBeginStringOrEmpty(s *scanner, c byte) int {
 
 // stateBeginString is the state after reading `{"key": value,`.
 func stateBeginString(s *scanner, c byte) int {
-	if c <= ' ' && isSpace(c) {
+	if isSpace(c) {
 		return scanSkipSpace
 	}
 	if c == '"' {
@@ -275,7 +282,7 @@ func stateEndValue(s *scanner, c byte) int {
 		s.endTop = true
 		return stateEndTop(s, c)
 	}
-	if c <= ' ' && isSpace(c) {
+	if isSpace(c) {
 		s.step = stateEndValue
 		return scanSkipSpace
 	}