[wasm] Validate the alignment of load and store instructions.

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 c4f6c1679a0bfb89d6d1b9c9c9197305e25aeca2..cab20b40daa91b21e82b85a07c359ebfa8144daf 100644
--- a/src/wasm/ast-decoder.h
+++ b/src/wasm/ast-decoder.h
@@ -5,6 +5,8 @@
 #ifndef V8_WASM_AST_DECODER_H_
 #define V8_WASM_AST_DECODER_H_
 
+#include "src/base/bits.h"
+#include "src/machine-type.h"
 #include "src/signature.h"
 #include "src/wasm/decoder.h"
 #include "src/wasm/wasm-opcodes.h"
@@ -183,10 +185,17 @@ struct MemoryAccessOperand {
   uint32_t alignment;
   uint32_t offset;
   unsigned length;
-  inline MemoryAccessOperand(Decoder* decoder, const byte* pc) {
+  inline MemoryAccessOperand(Decoder* decoder, const byte* pc,

[titzer, 2016/08/26 08:24:17]

Why not just pass the maximum alignment size here? Then the LOAD_CASE macros can
get it from sizeof(ctype)?

[ahaas, 2016/09/01 17:18:29]

Done.

+                             MachineType type) {
     unsigned alignment_length;
     alignment =
         decoder->checked_read_u32v(pc, 1, &alignment_length, "alignment");
+    if (type != MachineType::None() &&
+        ElementSizeLog2Of(type.representation()) <
+            static_cast<int>(alignment)) {
+      decoder->error(pc,
+                     "alignment must be less or equal to natural alignment");
+    }
     unsigned offset_length;
     offset = decoder->checked_read_u32v(pc, 1 + alignment_length,
                                         &offset_length, "offset");