From 562eae16681ed11bd085151b8dcec690cf0117ca Mon Sep 17 00:00:00 2001
From: Alon Zakai <azakai@google.com>
Date: Thu, 20 Oct 2022 10:19:46 -0700
Subject: Remove excessive validation that is not in the wasm spec (#5167)

Specifically if a segment offset was a const, we checked that it made sense. But the
wasm spec doesn't do that, and it actually causes some issues (#5163).

In theory this extra validation might be useful - compile-time error rather than runtime -
but if we want this it should probably be an optional thing, like an opt-in flag or a --lint
pass or such.
---
 src/wasm/wasm-validator.cpp | 29 +----------------------------
 1 file changed, 1 insertion(+), 28 deletions(-)

(limited to 'src/wasm/wasm-validator.cpp')

diff --git a/src/wasm/wasm-validator.cpp b/src/wasm/wasm-validator.cpp
index 0e7566528..642efac19 100644
--- a/src/wasm/wasm-validator.cpp
+++ b/src/wasm/wasm-validator.cpp
@@ -2909,27 +2909,7 @@ static bool checkSegmentOffset(Expression* curr,
                                Address add,
                                Address max,
                                FeatureSet features) {
-  if (!Properties::isValidInConstantExpression(curr, features)) {
-    return false;
-  }
-  auto* c = curr->dynCast<Const>();
-  if (!c) {
-    // Unless the instruction is actually a const instruction, we don't
-    // currently try to evaluate it.
-    // TODO: Attempt to evaluate other expressions that might also be const
-    // such as `global.get` or more complex instruction sequences involving
-    // add/sub/mul/etc.
-    return true;
-  }
-  uint64_t raw = c->value.getInteger();
-  if (raw > std::numeric_limits<Address::address32_t>::max()) {
-    return false;
-  }
-  if (raw + uint64_t(add) > std::numeric_limits<Address::address32_t>::max()) {
-    return false;
-  }
-  Address offset = raw;
-  return offset + add <= max;
+  return Properties::isValidInConstantExpression(curr, features);
 }
 
 void FunctionValidator::validateAlignment(
@@ -3231,13 +3211,6 @@ static void validateDataSegments(Module& module, ValidationInfo& info) {
                                            module.features),
                         segment->offset,
                         "memory segment offset should be reasonable");
-      if (segment->offset->is<Const>()) {
-        auto start = segment->offset->cast<Const>()->value.getUnsigned();
-        auto end = start + size;
-        info.shouldBeTrue(end <= memory->initial * Memory::kPageSize,
-                          segment->data.size(),
-                          "segment size should fit in memory (end)");
-      }
       FunctionValidator(module, &info).validate(segment->offset);
       // If the memory is imported we don't actually know its initial size.
       // Specifically wasm dll's import a zero sized memory which is perfectly
-- 
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