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Date: Mon, 21 Jul 2014 14:17:47 +0200
From: Florian Weimer <>
Subject: Re: Re: glibc locale issues

On 07/14/2014 04:15 AM, Tavis Ormandy wrote:
> Tavis Ormandy <> wrote:
>> I just remembered another charset issues I had looked into but abandoned.
>> First of all, I think the need_so logic in gconv_trans is broken, but even
>> if it worked there is an off by one error in __gconv_translit_find() (it
>> does + 3 instead of + 3 + 1 in the allocation.
> To be clear, I suspect this is exploitable. It would be nice if you could
> modify the buffer such that gconv will open a path with a string you've
> appended it (e.g. CHARSET=//. pkexec ./../../../../tmp/,

This is about the glib part and the alias processing, right?

iconv/gconv_charset.h:strip() normalizes the transliteration argument to 
iconv_open, so the resulting file names follow a particular pattern, and 
there cannot be enough slashes to ascend to a writable directory.

> if not maybe the one byte overflow is still exploitable.

Hmm.  How likely is that?  It overflows in to malloc metadata, and the 
glibc malloc hardening should catch that these days.

Florian Weimer / Red Hat Product Security

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