Fix integer overflow on extension range parsing when specifying MAX_INT as an extension number.

PiperOrigin-RevId: 570084841

src/google/protobuf/compiler/parser.cc

@@ -1695,6 +1695,11 @@ bool Parser::ParseExtensions(DescriptorProto* message,
           location, DescriptorProto::ExtensionRange::kStartFieldNumber);
       start_token = input_->current();
       DO(ConsumeInteger(&start, "Expected field number range."));
+
+      if (start == std::numeric_limits<int>::max()) {
+        RecordError("Field number out of bounds.");
+        return false;
+      }
     }
 
     if (TryConsume("to")) {
@@ -1707,6 +1712,11 @@ bool Parser::ParseExtensions(DescriptorProto* message,
         end = kMaxRangeSentinel - 1;
       } else {
         DO(ConsumeInteger(&end, "Expected integer."));
+
+        if (end == std::numeric_limits<int>::max()) {
+          RecordError("Field number out of bounds.");
+          return false;
+        }
       }
     } else {
       LocationRecorder end_location(

src/google/protobuf/compiler/parser_unittest.cc

@@ -930,6 +930,35 @@ TEST_F(ParseMessageTest, CompoundExtensionRange) {
       "}");
 }
 
+TEST_F(ParseMessageTest, MaxIntExtensionDoesNotOverflow) {
+  ExpectHasErrors(
+      R"(
+        syntax = "proto2";
+        message TestMessage {
+          extensions 2147483647;
+        }
+      )",
+      "3:31: Field number out of bounds.\n");
+  error_collector_.text_.clear();
+  ExpectHasErrors(
+      R"(
+        syntax = "proto2";
+        message TestMessage {
+          extensions 1 to 2147483647;
+        }
+      )",
+      "3:36: Field number out of bounds.\n");
+  error_collector_.text_.clear();
+  ExpectHasErrors(
+      R"(
+        syntax = "proto2";
+        message TestMessage {
+          extensions 2147483647 to 2147483647;
+        }
+      )",
+      "3:32: Field number out of bounds.\n");
+}
+
 TEST_F(ParseMessageTest, CompoundExtensionRangeWithOptions) {
   ExpectParsesTo(
       "message TestMessage {\n"