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[EH] Fuzzer: Fix infinite loop with nested exnrefs #7294

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Merged
kripken merged 1 commit into from
Feb 14, 2025
Merged

[EH] Fuzzer: Fix infinite loop with nested exnrefs #7294

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3 changes: 3 additions & 0 deletions src/tools/fuzzing.h
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Original file line number Diff line number Diff line change
Expand Up @@ -200,6 +200,9 @@ class TranslateToFuzzReader {

Index numAddedFunctions = 0;

// The name of an empty tag.
Name trivialTag;

// RAII helper for managing the state used to create a single function.
struct FunctionCreationContext {
TranslateToFuzzReader& parent;
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24 changes: 21 additions & 3 deletions src/tools/fuzzing/fuzzing.cpp
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Expand Up @@ -4825,10 +4825,28 @@ Expression* TranslateToFuzzReader::makeI31Get(Type type) {

Expression* TranslateToFuzzReader::makeThrow(Type type) {
assert(type == Type::unreachable);
if (wasm.tags.empty()) {
addTag();
Tag* tag;
if (trivialNesting) {
// We are nested under a makeTrivial call, so only emit something trivial.
// Get (or create) a trivial tag, so we have no operands (and will not call
// make(), below). Otherwise, we might recurse very deeply if we threw a
// tag that contains an exnref (for which we may end up creating yet another
// throw in a try).
if (!trivialTag) {
auto newTag = builder.makeTag(Names::getValidTagName(wasm, "tag$"),
Signature(Type::none, Type::none));
tag = wasm.addTag(std::move(newTag));
trivialTag = tag->name;
} else {
tag = wasm.getTag(trivialTag);
}
} else {
// Get a random tag, adding a random one if necessary.
if (wasm.tags.empty()) {
addTag();
}
tag = pick(wasm.tags).get();
}
auto* tag = pick(wasm.tags).get();
auto tagType = tag->params();
std::vector<Expression*> operands;
for (auto t : tagType) {
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