From: Rich Felker <dalias@libc.org>
To: musl@lists.openwall.com
Subject: Re: [musl] [PATCH] harden against unauthorized writes to the atexit function lists
Date: Tue, 1 Dec 2020 20:37:07 -0500 [thread overview]
Message-ID: <20201202013707.GU534@brightrain.aerifal.cx> (raw)
In-Reply-To: <20201202005539.6418-1-ariadne@dereferenced.org>
On Tue, Dec 01, 2020 at 05:55:39PM -0700, Ariadne Conill wrote:
> previously, the first atexit list block was stored in BSS, which means an
> attacker could potentially ascertain its location and modify it, allowing
> for its abuse as a code execution mechanism.
>
> by moving the atexit list into a series of anonymous mmaped pages, we can
> use mprotect to protect the atexit lists by keeping them readonly when they
> are not being mutated by the __cxa_atexit() function.
This is a non-starter. atexit is specifically required by the standard
to succeed when called no more than 32 times, which is why we have 32
built-in slots that always exist. If you really want to pursue
something here it should probably just be protecting the pointers with
some secret...
Rich
next prev parent reply other threads:[~2020-12-02 1:37 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-02 0:55 Ariadne Conill
2020-12-02 1:37 ` Rich Felker [this message]
2020-12-03 17:55 ` Matthew Maurer
2020-12-03 19:16 ` Rich Felker
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