I got the same crash,how to avoid this kind of problem？I think this may be
due to our special writing, but what are the specific possibilities?
在 2015年1月24日星期六 UTC+8上午7:19:05，Jana Baran写道：
>
> Potential overflow problem occurs all around the protobuf code.
> For example see message_lite.cc
>
> "
> bool MessageLite::AppendPartialToString(string* output) const {
> int old_size = output->size();
> int byte_size = ByteSize();
> STLStringResizeUninitialized(output, old_size + byte_size);
> uint8* start = reinterpret_cast<uint8*>(string_as_array(output) +
> old_size);
> uint8* end = SerializeWithCachedSizesToArray(start);
> if (end - start != byte_size) {
> ByteSizeConsistencyError(byte_size, ByteSize(), end - start);
> }
> return true;
> }
> "
>
> First two lines, size_t (unsigned 64b on a 64b architecture) is cast to
> int (signed 32b).
>
> Third line problem is 'old_size + byte_size' which can overflow. There
> should be a check before the summation like:
>
> size_t new_size = 0;
> if (std::numeric_limits<size_t>::max() - old_size < byte_size) {
> // we have a problem
> } else {
> new_size = old_size + byte_size;
> }
>
> STLStringResizeUninitialized correctly takes size_t as an input but you
> need to cast before the summation and not after, like "(size_t)old_size +
> byte_size"
>
> Next two lines: 'start' and 'end' is of type uint8 which is unsigned 8bit
> integer. On next line this uint8 is compared with byte_size (1B variable
> compared with 4B variable) and ByteSizeConsistencyError is called when we
> are not happy with the comparison.
>
> Now funny part is the comment above MessageLite::ByteSizeConsistencyError
> method which states:
>
> "...If serialization produces a different number of bytes than expected,
> we call this function, which crashes. The problem could be due to a bug in
> the protobuf implementation..."
>
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