Re: Crash in gconv_db.c

[Florian Weimer <fweimer@redhat.com>]

* Abhidnya Joshi:

> In increment_counter function, do we have to handle integer overflow like this?
>
>
> if (step->__counter == INT_MAX)
> {
> step->__counter = 1
> }
> if (step->__counter++ == 0)
> { ....
> }
>
> I do not understand what will be impact of this on different "steps".
> If step->__counter gets set to 0 and step->__modname is NULL
> then we see the segfault as mentioned earlier.

The steps array has reference counts in the array *elements*, which is
wrong.  We ran into this a couple of months ago when we tried to fix a
memory leak.  This is the reason why I have limited confidence in the
correctness of the reference counting.

I looked at what it would take to reproduce the overflow with repeated
iconv_open calls, and I estimate that 1.2 TiB of RAM are required, so I
have not reproduced that yet.

But there could be more subtle ways to trigger counter overflow, like
uselocale followed by pthread_exit.  Without a reproducer, we are in the
dark here unfortunately.

Thanks,
Florian