[wasm] improve handling of malformed input

src/wasm/ast-decoder.h

Index: src/wasm/ast-decoder.h
diff --git a/src/wasm/ast-decoder.h b/src/wasm/ast-decoder.h
index 9e96053a6ce035773fbe9f992e24d2f0e8430c35..d9af39dc903fd3aaf3db1f6836881e4d29a56718 100644
--- a/src/wasm/ast-decoder.h
+++ b/src/wasm/ast-decoder.h
@@ -25,7 +25,7 @@ namespace wasm {
 struct LocalIndexOperand {
   uint32_t index;
   LocalType type;
-  int length;
+  unsigned length;
 
   inline LocalIndexOperand(Decoder* decoder, const byte* pc) {
     index = decoder->checked_read_u32v(pc, 1, &length, "local index");
@@ -35,7 +35,7 @@ struct LocalIndexOperand {
 
 struct ImmI8Operand {
   int8_t value;
-  int length;
+  unsigned length;
   inline ImmI8Operand(Decoder* decoder, const byte* pc) {
     value = bit_cast<int8_t>(decoder->checked_read_u8(pc, 1, "immi8"));
     length = 1;
@@ -44,7 +44,7 @@ struct ImmI8Operand {
 
 struct ImmI32Operand {
   int32_t value;
-  int length;
+  unsigned length;
   inline ImmI32Operand(Decoder* decoder, const byte* pc) {
     value = decoder->checked_read_i32v(pc, 1, &length, "immi32");
   }
@@ -52,7 +52,7 @@ struct ImmI32Operand {
 
 struct ImmI64Operand {
   int64_t value;
-  int length;
+  unsigned length;
   inline ImmI64Operand(Decoder* decoder, const byte* pc) {
     value = decoder->checked_read_i64v(pc, 1, &length, "immi64");
   }
@@ -60,7 +60,7 @@ struct ImmI64Operand {
 
 struct ImmF32Operand {
   float value;
-  int length;
+  unsigned length;
   inline ImmF32Operand(Decoder* decoder, const byte* pc) {
     value = bit_cast<float>(decoder->checked_read_u32(pc, 1, "immf32"));
     length = 4;
@@ -69,7 +69,7 @@ struct ImmF32Operand {
 
 struct ImmF64Operand {
   double value;
-  int length;
+  unsigned length;
   inline ImmF64Operand(Decoder* decoder, const byte* pc) {
     value = bit_cast<double>(decoder->checked_read_u64(pc, 1, "immf64"));
     length = 8;
@@ -80,7 +80,7 @@ struct GlobalIndexOperand {
   uint32_t index;
   LocalType type;
   MachineType machine_type;
-  int length;
+  unsigned length;
 
   inline GlobalIndexOperand(Decoder* decoder, const byte* pc) {
     index = decoder->checked_read_u32v(pc, 1, &length, "global index");
@@ -94,10 +94,10 @@ struct BreakDepthOperand {
   uint32_t arity;
   uint32_t depth;
   Control* target;
-  int length;
+  unsigned length;
   inline BreakDepthOperand(Decoder* decoder, const byte* pc) {
-    int len1 = 0;
-    int len2 = 0;
+    unsigned len1 = 0;
+    unsigned len2 = 0;
     arity = decoder->checked_read_u32v(pc, 1, &len1, "argument count");
     depth = decoder->checked_read_u32v(pc, 1 + len1, &len2, "break depth");
     length = len1 + len2;
@@ -109,10 +109,10 @@ struct CallIndirectOperand {
   uint32_t arity;
   uint32_t index;
   FunctionSig* sig;
-  int length;
+  unsigned length;
   inline CallIndirectOperand(Decoder* decoder, const byte* pc) {
-    int len1 = 0;
-    int len2 = 0;
+    unsigned len1 = 0;
+    unsigned len2 = 0;
     arity = decoder->checked_read_u32v(pc, 1, &len1, "argument count");
     index = decoder->checked_read_u32v(pc, 1 + len1, &len2, "signature index");
     length = len1 + len2;
@@ -124,10 +124,10 @@ struct CallFunctionOperand {
   uint32_t arity;
   uint32_t index;
   FunctionSig* sig;
-  int length;
+  unsigned length;
   inline CallFunctionOperand(Decoder* decoder, const byte* pc) {
-    int len1 = 0;
-    int len2 = 0;
+    unsigned len1 = 0;
+    unsigned len2 = 0;
     arity = decoder->checked_read_u32v(pc, 1, &len1, "argument count");
     index = decoder->checked_read_u32v(pc, 1 + len1, &len2, "function index");
     length = len1 + len2;
@@ -139,10 +139,10 @@ struct CallImportOperand {
   uint32_t arity;
   uint32_t index;
   FunctionSig* sig;
-  int length;
+  unsigned length;
   inline CallImportOperand(Decoder* decoder, const byte* pc) {
-    int len1 = 0;
-    int len2 = 0;
+    unsigned len1 = 0;
+    unsigned len2 = 0;
     arity = decoder->checked_read_u32v(pc, 1, &len1, "argument count");
     index = decoder->checked_read_u32v(pc, 1 + len1, &len2, "import index");
     length = len1 + len2;
@@ -154,13 +154,15 @@ struct BranchTableOperand {
   uint32_t arity;
   uint32_t table_count;
   const byte* table;
-  int length;
+  unsigned length;
   inline BranchTableOperand(Decoder* decoder, const byte* pc) {
-    int len1 = 0;
-    int len2 = 0;
+    unsigned len1 = 0;
+    unsigned len2 = 0;
     arity = decoder->checked_read_u32v(pc, 1, &len1, "argument count");
     table_count =
         decoder->checked_read_u32v(pc, 1 + len1, &len2, "table count");
+    CHECK(table_count <= (UINT_MAX / sizeof(uint32_t)) - 1);

[bradnelson, 2016/06/24 18:40:47]

I believe by check, Ben meant invoke error on overflow.

+    CHECK(len1 + len2 <= UINT_MAX - (table_count + 1) * sizeof(uint32_t));
     length = len1 + len2 + (table_count + 1) * sizeof(uint32_t);
 
     uint32_t table_start = 1 + len1 + len2;
@@ -171,8 +173,8 @@ struct BranchTableOperand {
       table = nullptr;
     }
   }
-  inline uint32_t read_entry(Decoder* decoder, int i) {
-    DCHECK(i >= 0 && static_cast<uint32_t>(i) <= table_count);
+  inline uint32_t read_entry(Decoder* decoder, unsigned i) {
+    DCHECK(i <= table_count);
     return table ? decoder->read_u32(table + i * sizeof(uint32_t)) : 0;
   }
 };
@@ -180,12 +182,12 @@ struct BranchTableOperand {
 struct MemoryAccessOperand {
   uint32_t alignment;
   uint32_t offset;
-  int length;
+  unsigned length;
   inline MemoryAccessOperand(Decoder* decoder, const byte* pc) {
-    int alignment_length;
+    unsigned alignment_length;
     alignment =
         decoder->checked_read_u32v(pc, 1, &alignment_length, "alignment");
-    int offset_length;
+    unsigned offset_length;
     offset = decoder->checked_read_u32v(pc, 1 + alignment_length,
                                         &offset_length, "offset");
     length = alignment_length + offset_length;
@@ -194,7 +196,7 @@ struct MemoryAccessOperand {
 
 struct ReturnArityOperand {
   uint32_t arity;
-  int length;
+  unsigned length;
 
   inline ReturnArityOperand(Decoder* decoder, const byte* pc) {
     arity = decoder->checked_read_u32v(pc, 1, &length, "return count");
@@ -262,10 +264,10 @@ BitVector* AnalyzeLoopAssignmentForTesting(Zone* zone, size_t num_locals,
                                            const byte* start, const byte* end);
 
 // Computes the length of the opcode at the given address.
-int OpcodeLength(const byte* pc, const byte* end);
+unsigned OpcodeLength(const byte* pc, const byte* end);
 
 // Computes the arity (number of sub-nodes) of the opcode at the given address.
-int OpcodeArity(const byte* pc, const byte* end);
+unsigned OpcodeArity(const byte* pc, const byte* end);
 
 }  // namespace wasm
 }  // namespace internal