[WebAssembly] Validate exports when parsing object files

include/llvm/Object/Wasm.h

private:
   std::vector<wasm::WasmElemSegment> ElemSegments;
   std::vector<WasmSegment> DataSegments;
   std::vector<wasm::WasmFunction> Functions;
   std::vector<WasmSymbol> Symbols;
   ArrayRef<uint8_t> CodeSection;
   uint32_t StartFunction = -1;
   bool HasLinkingSection = false;
   wasm::WasmLinkingData LinkingData;
+  uint32_t NumImportedGlobals = 0;
+  uint32_t NumImportedFunctions = 0;
 
   StringMap<uint32_t> SymbolMap;
 };
 
 } // end namespace object
 
 inline raw_ostream &operator<<(raw_ostream &OS,
                                const object::WasmSymbol &Sym) {
   Sym.print(OS);
   return OS;
 }
 
 } // end namespace llvm
 
 #endif // LLVM_OBJECT_WASM_H

lib/Object/WasmObjectFile.cpp

Error WasmObjectFile::parseImportSection(const uint8_t *Ptr, const uint8_t *End) {
   Imports.reserve(Count);
   for (uint32_t i = 0; i < Count; i++) {
     wasm::WasmImport Im;
     Im.Module = readString(Ptr);
     Im.Field = readString(Ptr);
     Im.Kind = readUint8(Ptr);
     switch (Im.Kind) {
     case wasm::WASM_EXTERNAL_FUNCTION:
+      NumImportedFunctions++;
       Im.SigIndex = readVaruint32(Ptr);
       SymbolMap.try_emplace(Im.Field, Symbols.size());
       Symbols.emplace_back(Im.Field, WasmSymbol::SymbolType::FUNCTION_IMPORT,
                            Sections.size(), i);
       DEBUG(dbgs() << "Adding import: " << Symbols.back()
                    << " sym index:" << Symbols.size() << "\n");
       break;
     case wasm::WASM_EXTERNAL_GLOBAL:
+      NumImportedGlobals++;
       Im.Global.Type = readVarint7(Ptr);
       Im.Global.Mutable = readVaruint1(Ptr);
       SymbolMap.try_emplace(Im.Field, Symbols.size());
       Symbols.emplace_back(Im.Field, WasmSymbol::SymbolType::GLOBAL_IMPORT,
                            Sections.size(), i);
       DEBUG(dbgs() << "Adding import: " << Symbols.back()
                    << " sym index:" << Symbols.size() << "\n");
       break;
for (uint32_t i = 0; i < Count; i++) {
     Ex.Name = readString(Ptr);
     Ex.Kind = readUint8(Ptr);
     Ex.Index = readVaruint32(Ptr);
     WasmSymbol::SymbolType ExportType;
     bool MakeSymbol = false;
     switch (Ex.Kind) {
     case wasm::WASM_EXTERNAL_FUNCTION:
       ExportType = WasmSymbol::SymbolType::FUNCTION_EXPORT;
+      if (Ex.Index >= FunctionTypes.size() + NumImportedFunctions)
+        return make_error<GenericBinaryError>("Invalid function export",
+                                              object_error::parse_failed);
       MakeSymbol = true;
       break;
     case wasm::WASM_EXTERNAL_GLOBAL:
       ExportType = WasmSymbol::SymbolType::GLOBAL_EXPORT;
+      if (Ex.Index >= Globals.size() + NumImportedGlobals)
+        return make_error<GenericBinaryError>("Invalid global export",
+                                              object_error::parse_failed);
       MakeSymbol = true;
       break;
     case wasm::WASM_EXTERNAL_MEMORY:
     case wasm::WASM_EXTERNAL_TABLE:
       break;
     default:
       return make_error<GenericBinaryError>(
           "Unexpected export kind", object_error::parse_failed);

test/ObjectYAML/wasm/export_section.yaml

 # RUN: yaml2obj %s | obj2yaml | FileCheck %s
 --- !WASM
 FileHeader:
   Version:         0x00000001
 Sections:
+  - Type:            FUNCTION
+    FunctionTypes: [ 0, 0 ]
+  - Type:            GLOBAL
+    Globals:
+      - Type:        I32
+        Mutable:     false
+        InitExpr:
+          Opcode:          I64_CONST
+          Value:           32
+      - Type:        I32
+        Mutable:     false
+        InitExpr:
+          Opcode:          I64_CONST
+          Value:           64
   - Type:            EXPORT
     Exports:         
       - Name:            function_export
         Kind:            FUNCTION
         Index:           1
       - Name:            global_export
         Kind:            GLOBAL
         Index:           1

test/ObjectYAML/wasm/invalid_export.yaml

+# RUN: yaml2obj < %s | not obj2yaml 2>&1 | FileCheck %s
+
+--- !WASM
+FileHeader:
+  Version:         0x00000001
+Sections:
+  - Type:            EXPORT
+    Exports:
+      - Name:            invalid_function_index
+        Kind:            FUNCTION
+        Index:           0x00000001
+
+# CHECK: Error reading file: <stdin>: Invalid function export

test/tools/llvm-nm/wasm/exports.yaml

 # RUN: yaml2obj < %s | llvm-nm - | FileCheck %s
 
 # That wasm exports of functions and globals are displayed as global data and
 # code symbols.
 
 --- !WASM
 FileHeader:
   Version:         0x00000001
 Sections:
   - Type:            TYPE
     Signatures:
       - ReturnType:      I32
         ParamTypes:
           - I32
+  - Type:            FUNCTION
+    FunctionTypes: [ 0, 0, 0, 0, 0 ]
+  - Type:            GLOBAL
+    Globals:
+      - Type:        I32
+        Mutable:     false
+        InitExpr:
+          Opcode:          I64_CONST
+          Value:           32
+      - Type:        I32
+        Mutable:     false
+        InitExpr:
+          Opcode:          I64_CONST
+          Value:           64
+      - Type:        I32
+        Mutable:     false
+        InitExpr:
+          Opcode:          I64_CONST
+          Value:           1024
   - Type:            EXPORT
     Exports:
       - Name:            foo
         Kind:            FUNCTION
         Index:           0x00000004
       - Name:            bar
         Kind:            GLOBAL
         Index:           0x00000002
 
 # CHECK: 00000002 D bar
 # CHECK: 00000004 T foo

test/tools/llvm-nm/wasm/weak-symbols.yaml

 # RUN: yaml2obj < %s | llvm-nm - | FileCheck %s
 
 # That wasm exports of functions and globals are displayed as global data and
 # code symbols.
 
 --- !WASM
 FileHeader:
   Version:         0x00000001
 Sections:
   - Type:            TYPE
     Signatures:
       - ReturnType:      I32
         ParamTypes:
           - I32
+  - Type:            FUNCTION
+    FunctionTypes: [ 0, 0, 0, 0 ]
   - Type:            IMPORT
     Imports:
       - Module:          env
         Field:           weak_import_func
         Kind:            FUNCTION
         SigIndex:        0
       - Module:          env
         Field:           weak_import_data
         Kind:            GLOBAL
         GlobalType:      I32
         GlobalMutable:   false
+  - Type:            GLOBAL
+    Globals:
+      - Type:        I32
+        Mutable:     false
+        InitExpr:
+          Opcode:          I64_CONST
+          Value:           32
+      - Type:        I32
+        Mutable:     false
+        InitExpr:
+          Opcode:          I64_CONST
+          Value:           64
+      - Type:        I32
+        Mutable:     false
+        InitExpr:
+          Opcode:          I64_CONST
+          Value:           1024
   - Type:            EXPORT
     Exports:
       - Name:            weak_global_func
         Kind:            FUNCTION
         Index:           0x00000004
       - Name:            weak_global_data
         Kind:            GLOBAL
         Index:           0x00000002