[Libreoffice-commits] update string copy semantics to be undefined in a non-crashing way

Norbert Thiebaud nthiebaud at gmail.com
Thu Oct 4 03:28:52 PDT 2012

On Thu, Oct 4, 2012 at 4:34 AM, Stephan Bergmann <sbergman at redhat.com> wrote:
> Given that "it is an error for X to happen" and "if X happens, behaviour is
> undefined" have exactly the same meaning (at least in my understanding of
> computing), I wonder whether this is just a harmless rephrasing, or whether
> there is a deeper misunderstanding lurking there.

In my mind there is a distinction:
if an API declare that something 'an error' I expect it to give a
return code, an exception, a signal... something bad
if something is said to be 'undefined', then the call can do anything,
including nothing or returning random result...

> Note how the original code above prevented problems with overflowing
> beginIndex + count.

The only exploitable way to misuse that would be to be able to read
past the input and into memory that contain sensitive / secret
information... and being able to disclose it that way...
Although not impossible, it is hard to conceive a scenario where that
would lead to a practical exploit.
(by opposition a write overflow is much more likely to lead to a
practical exploit)


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