[wasm] improve handling of malformed input

src/wasm/module-decoder.cc

Index: src/wasm/module-decoder.cc
diff --git a/src/wasm/module-decoder.cc b/src/wasm/module-decoder.cc
index 48f59cefa82bdf1d293da3eb529d4244e7dc2485..a0d3ab7dac27af795f748b1158f913f966cddce9 100644
--- a/src/wasm/module-decoder.cc
+++ b/src/wasm/module-decoder.cc
@@ -108,7 +108,7 @@ class ModuleDecoder : public Decoder {
       pos = pc_;
 
       // Read the section name.
-      int string_leb_length = 0;
+      unsigned string_leb_length = 0;
       uint32_t string_length =
           consume_u32v(&string_leb_length, "section name length");
       const byte* section_name_start = pc_;
@@ -126,7 +126,7 @@ class ModuleDecoder : public Decoder {
           WasmSection::lookup(section_name_start, string_length);
 
       // Read and check the section size.
-      int section_leb_length = 0;
+      unsigned section_leb_length = 0;
       uint32_t section_length =
           consume_u32v(&section_leb_length, "section length");
       if (!checkAvailable(section_length)) {
@@ -144,14 +144,14 @@ class ModuleDecoder : public Decoder {
           limit_ = pc_;
           break;
         case WasmSection::Code::Memory: {
-          int length;
+          unsigned length;
           module->min_mem_pages = consume_u32v(&length, "min memory");
           module->max_mem_pages = consume_u32v(&length, "max memory");
           module->mem_export = consume_u8("export memory") != 0;
           break;
         }
         case WasmSection::Code::Signatures: {
-          int length;
+          unsigned length;
           uint32_t signatures_count = consume_u32v(&length, "signatures count");
           module->signatures.reserve(SafeReserve(signatures_count));
           // Decode signatures.
@@ -165,7 +165,7 @@ class ModuleDecoder : public Decoder {
           break;
         }
         case WasmSection::Code::FunctionSignatures: {
-          int length;
+          unsigned length;
           uint32_t functions_count = consume_u32v(&length, "functions count");
           module->functions.reserve(SafeReserve(functions_count));
           for (uint32_t i = 0; i < functions_count; i++) {
@@ -182,7 +182,7 @@ class ModuleDecoder : public Decoder {
           break;
         }
         case WasmSection::Code::FunctionBodies: {
-          int length;
+          unsigned length;
           const byte* pos = pc_;
           uint32_t functions_count = consume_u32v(&length, "functions count");
           if (functions_count != module->functions.size()) {
@@ -193,7 +193,7 @@ class ModuleDecoder : public Decoder {
           }
           for (uint32_t i = 0; i < functions_count; i++) {
             WasmFunction* function = &module->functions[i];
-            int length;
+            unsigned length;
             uint32_t size = consume_u32v(&length, "body size");
             function->code_start_offset = pc_offset();
             function->code_end_offset = pc_offset() + size;
@@ -208,7 +208,7 @@ class ModuleDecoder : public Decoder {
           break;
         }
         case WasmSection::Code::Names: {
-          int length;
+          unsigned length;
           const byte* pos = pc_;
           uint32_t functions_count = consume_u32v(&length, "functions count");
           if (functions_count != module->functions.size()) {
@@ -235,7 +235,7 @@ class ModuleDecoder : public Decoder {
           break;
         }
         case WasmSection::Code::Globals: {
-          int length;
+          unsigned length;
           uint32_t globals_count = consume_u32v(&length, "globals count");
           module->globals.reserve(SafeReserve(globals_count));
           // Decode globals.
@@ -250,7 +250,7 @@ class ModuleDecoder : public Decoder {
           break;
         }
         case WasmSection::Code::DataSegments: {
-          int length;
+          unsigned length;
           uint32_t data_segments_count =
               consume_u32v(&length, "data segments count");
           module->data_segments.reserve(SafeReserve(data_segments_count));
@@ -271,7 +271,7 @@ class ModuleDecoder : public Decoder {
         case WasmSection::Code::FunctionTable: {
           // An indirect function table requires functions first.
           CheckForFunctions(module, section);
-          int length;
+          unsigned length;
           uint32_t function_table_count =
               consume_u32v(&length, "function table count");
           module->function_table.reserve(SafeReserve(function_table_count));
@@ -306,7 +306,7 @@ class ModuleDecoder : public Decoder {
           break;
         }
         case WasmSection::Code::ImportTable: {
-          int length;
+          unsigned length;
           uint32_t import_table_count =
               consume_u32v(&length, "import table count");
           module->import_table.reserve(SafeReserve(import_table_count));
@@ -339,7 +339,7 @@ class ModuleDecoder : public Decoder {
         case WasmSection::Code::ExportTable: {
           // Declares an export table.
           CheckForFunctions(module, section);
-          int length;
+          unsigned length;
           uint32_t export_table_count =
               consume_u32v(&length, "export table count");
           module->export_table.reserve(SafeReserve(export_table_count));
@@ -471,7 +471,7 @@ class ModuleDecoder : public Decoder {
   // Decodes a single data segment entry inside a module starting at {pc_}.
   void DecodeDataSegmentInModule(WasmModule* module, WasmDataSegment* segment) {
     const byte* start = pc_;
-    int length;
+    unsigned length;
     segment->dest_addr = consume_u32v(&length, "destination");
     segment->source_size = consume_u32v(&length, "source size");
     segment->source_offset = static_cast<uint32_t>(pc_ - start_);
@@ -555,7 +555,7 @@ class ModuleDecoder : public Decoder {
   // Reads a length-prefixed string, checking that it is within bounds. Returns
   // the offset of the string, and the length as an out parameter.
   uint32_t consume_string(uint32_t* length, bool validate_utf8) {
-    int varint_length;
+    unsigned varint_length;
     *length = consume_u32v(&varint_length, "string length");
     uint32_t offset = pc_offset();
     TRACE("  +%u  %-20s: (%u bytes)\n", offset, "string", *length);
@@ -568,7 +568,7 @@ class ModuleDecoder : public Decoder {
 
   uint32_t consume_sig_index(WasmModule* module, FunctionSig** sig) {
     const byte* pos = pc_;
-    int length;
+    unsigned length;
     uint32_t sig_index = consume_u32v(&length, "signature index");
     if (sig_index >= module->signatures.size()) {
       error(pos, pos, "signature index %u out of bounds (%d signatures)",
@@ -582,7 +582,7 @@ class ModuleDecoder : public Decoder {
 
   uint32_t consume_func_index(WasmModule* module, WasmFunction** func) {
     const byte* pos = pc_;
-    int length;
+    unsigned length;
     uint32_t func_index = consume_u32v(&length, "function index");
     if (func_index >= module->functions.size()) {
       error(pos, pos, "function index %u out of bounds (%d functions)",
@@ -657,7 +657,7 @@ class ModuleDecoder : public Decoder {
             kWasmFunctionTypeForm, form);
       return nullptr;
     }
-    int length;
+    unsigned length;
     // parse parameter types
     uint32_t param_count = consume_u32v(&length, "param count");
     std::vector<LocalType> params;