[wasm] improve handling of malformed input

src/wasm/decoder.h

 // Copyright 2015 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_WASM_DECODER_H_
 #define V8_WASM_DECODER_H_
 
 #include "src/base/compiler-specific.h"
 #include "src/base/smart-pointers.h"
 #include "src/flags.h"
@@ skipping 28 matching lines @@
   Decoder(const byte* start, const byte* end)
       : start_(start),
         pc_(start),
         limit_(end),
         end_(end),
         error_pc_(nullptr),
         error_pt_(nullptr) {}
 
   virtual ~Decoder() {}
 
-  inline bool check(const byte* base, int offset, int length, const char* msg) {
+  inline bool check(const byte* base, unsigned offset, unsigned length,
+                    const char* msg) {
     DCHECK_GE(base, start_);
     if ((base + offset + length) > limit_) {
       error(base, base + offset, "%s", msg);
       return false;
     }
     return true;
   }
 
   // Reads a single 8-bit byte, reporting an error if out of bounds.
-  inline uint8_t checked_read_u8(const byte* base, int offset,
+  inline uint8_t checked_read_u8(const byte* base, unsigned offset,
                                  const char* msg = "expected 1 byte") {
     return check(base, offset, 1, msg) ? base[offset] : 0;
   }
 
   // Reads 16-bit word, reporting an error if out of bounds.
-  inline uint16_t checked_read_u16(const byte* base, int offset,
+  inline uint16_t checked_read_u16(const byte* base, unsigned offset,
                                    const char* msg = "expected 2 bytes") {
     return check(base, offset, 2, msg) ? read_u16(base + offset) : 0;
   }
 
   // Reads 32-bit word, reporting an error if out of bounds.
-  inline uint32_t checked_read_u32(const byte* base, int offset,
+  inline uint32_t checked_read_u32(const byte* base, unsigned offset,
                                    const char* msg = "expected 4 bytes") {
     return check(base, offset, 4, msg) ? read_u32(base + offset) : 0;
   }
 
   // Reads 64-bit word, reporting an error if out of bounds.
-  inline uint64_t checked_read_u64(const byte* base, int offset,
+  inline uint64_t checked_read_u64(const byte* base, unsigned offset,
                                    const char* msg = "expected 8 bytes") {
     return check(base, offset, 8, msg) ? read_u64(base + offset) : 0;
   }
 
   // Reads a variable-length unsigned integer (little endian).
-  uint32_t checked_read_u32v(const byte* base, int offset, int* length,
+  uint32_t checked_read_u32v(const byte* base, unsigned offset,
+                             unsigned* length,
                              const char* msg = "expected LEB32") {
     return checked_read_leb<uint32_t, false>(base, offset, length, msg);
   }
 
   // Reads a variable-length signed integer (little endian).
-  int32_t checked_read_i32v(const byte* base, int offset, int* length,
+  int32_t checked_read_i32v(const byte* base, unsigned offset, unsigned* length,
                             const char* msg = "expected SLEB32") {
     uint32_t result =
         checked_read_leb<uint32_t, true>(base, offset, length, msg);
     if (*length == 5) return bit_cast<int32_t>(result);
     if (*length > 0) {
       int shift = 32 - 7 * *length;
       // Perform sign extension.
       return bit_cast<int32_t>(result << shift) >> shift;
     }
     return 0;
   }
 
   // Reads a variable-length unsigned integer (little endian).
-  uint64_t checked_read_u64v(const byte* base, int offset, int* length,
+  uint64_t checked_read_u64v(const byte* base, unsigned offset,
+                             unsigned* length,
                              const char* msg = "expected LEB64") {
     return checked_read_leb<uint64_t, false>(base, offset, length, msg);
   }
 
   // Reads a variable-length signed integer (little endian).
-  int64_t checked_read_i64v(const byte* base, int offset, int* length,
+  int64_t checked_read_i64v(const byte* base, unsigned offset, unsigned* length,
                             const char* msg = "expected SLEB64") {
     uint64_t result =
         checked_read_leb<uint64_t, true>(base, offset, length, msg);
     if (*length == 10) return bit_cast<int64_t>(result);
     if (*length > 0) {
       int shift = 64 - 7 * *length;
       // Perform sign extension.
       return bit_cast<int64_t>(result << shift) >> shift;
     }
     return 0;
@@ skipping 222 matching lines @@
   const byte* start_;
   const byte* pc_;
   const byte* limit_;
   const byte* end_;
   const byte* error_pc_;
   const byte* error_pt_;
   base::SmartArrayPointer<char> error_msg_;
 
  private:
   template <typename IntType, bool is_signed>
-  IntType checked_read_leb(const byte* base, int offset, int* length,
+  IntType checked_read_leb(const byte* base, unsigned offset, unsigned* length,
                            const char* msg) {
     if (!check(base, offset, 1, msg)) {
       *length = 0;
       return 0;
     }
 
     const int kMaxLength = (sizeof(IntType) * 8 + 6) / 7;
     const byte* ptr = base + offset;
     const byte* end = ptr + kMaxLength;
     if (end > limit_) end = limit_;
     int shift = 0;
     byte b = 0;
     IntType result = 0;
     while (ptr < end) {
       b = *ptr++;
       result = result | (static_cast<IntType>(b & 0x7F) << shift);
       if ((b & 0x80) == 0) break;
       shift += 7;
     }
     DCHECK_LE(ptr - (base + offset), kMaxLength);
-    *length = static_cast<int>(ptr - (base + offset));
+    *length = static_cast<unsigned>(ptr - (base + offset));
     if (ptr == end) {
       // Check there are no bits set beyond the bitwidth of {IntType}.
       const int kExtraBits = (1 + kMaxLength * 7) - (sizeof(IntType) * 8);
       const byte kExtraBitsMask =
           static_cast<byte>((0xFF << (8 - kExtraBits)) & 0xFF);
       int extra_bits_value;
       if (is_signed) {
         // A signed-LEB128 must sign-extend the final byte, excluding its
         // most-signifcant bit. e.g. for a 32-bit LEB128:
         //   kExtraBits = 4
@@ skipping 17 matching lines @@
     return result;
   }
 };
 
 #undef TRACE
 }  // namespace wasm
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_WASM_DECODER_H_