RFR (XS): 8199010: attachListener.hpp: Fix potential null termination issue found by coverity scans

[Langer, Christoph]

Hi Chris, David and Thomas,

I took a closer look now, too. Funny that the original change was contributed by my colleagues because of coverity and that they didn't do it completely right. �� As a code comment in our attachListener.hpp suggests, the '0' termination to please coverity was added far earlier than JDK-8140482 was done.

So, yes, in fact the input to the "set_name" and "set_arg" methods should never exceed the maximum length values as per the current code in the OpenJDK. These methods are called from the various platform specific attachListener_<os>.cpp files. And in each of these places the length is already checked and violations get handled. So with the assertion we merely guard against new code that doesn't do checking which can potentially come in.

So one can argue that the assertions are enough here and we can just do strcpy. In that case I would even support Thomas' suggestion to change the assertion into a guarantee as the input coming in from new code is not necessarily static but can be user input (who knows). And we should also turn the knob here to quiesce coverity since it is obviously not considering the possible call paths and the checks in them.

But on the other hand, one could be as conservative as it is now - I guess it doesn't bear too much of cost and this place of code is not performance critical. That means do the assertion in dbg builds and for opt effectively do a checked, truncating copy of the input data but avoiding JVM crashes or other errors due to unterminated strings.

I personally tend to do the second - but fine if I get overruled.

But, if we do the second, I'm still for memcpy as strncpy would do zero padding of the buffer which is not necessary and we have to write a terminating 0 as well to handle the case that inputlength > name_len_max (the case which should not happen but we want to protect against). That would mean my change stays as it is.

What shall I do now?

Best regards
Christoph