oss-security - Re: SEGV in `alloca(BIG)` and `long pl[BIG]`

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Date: Wed, 08 Feb 2023 10:42:19 +0100
From: Florian Weimer <fweimer@...hat.com>
To: Georgi Guninski <gguninski@...il.com>
Cc: oss-security@...ts.openwall.com
Subject: Re: SEGV in `alloca(BIG)` and `long pl[BIG]`

* Georgi Guninski:

> Inline are two C warez, which crash on
> `alloca(BIG)` and `long pl[BIG]`.
>
> I think alloca(BIG) should return error if BIG>max_signed_size_t.
> In C++ `new[BUG]` throws exception and core dumps.

Unfortunately, alloca cannot report an error, and there is no portable
way to discover stack boundaries anyway.  With -fstack-clash-protection,
we could reliably produce crashes, but the feature is somewhat
incomplete:

  Integer overflows in dynamically-sized stack allocations with
  -fstack-clash-protection
  <https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83697>

Thanks,
Florian

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