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Don't overread buffers. #303

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Merged
merged 1 commit into from
Aug 4, 2022
Merged

Don't overread buffers. #303

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16 changes: 12 additions & 4 deletions src/exports.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -485,13 +485,21 @@ Word get_buffer_bytes(Word type, Word start, Word length, Word ptr_ptr, Word siz
return WasmResult::BadArgument;
}
// Don't overread.
if (start + length > buffer->size()) {
if (start > buffer->size()) {
length = 0;
} else if (start + length > buffer->size()) {
length = buffer->size() - start;
}
if (length > 0) {
return buffer->copyTo(context->wasm(), start, length, ptr_ptr, size_ptr);
if (length == 0) {
if (!context->wasmVm()->setWord(ptr_ptr, Word(0))) {
return WasmResult::InvalidMemoryAccess;
}
if (!context->wasmVm()->setWord(size_ptr, Word(0))) {
return WasmResult::InvalidMemoryAccess;
}
return WasmResult::Ok;
}
return WasmResult::Ok;
return buffer->copyTo(context->wasm(), start, length, ptr_ptr, size_ptr);
}

Word get_buffer_status(Word type, Word length_ptr, Word flags_ptr) {
Expand Down