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Date: Wed, 20 Jul 2011 12:30:35 +0200
From: "Luka M." <paxcoder@...il.com>
To: musl@...ts.openwall.com
Subject: Re: cluts memcpy() test
On Wed, Jul 20, 2011 at 2:28 AM, Solar Designer <solar@...nwall.com> wrote:
> Luka, Rich -
>
> It'd be nice for cluts to detect issues like this:
>
> http://www.nodefense.org/eglibc.txt
>
> Maybe it already does?
>
Hey Alexander. Cluts doesn't test negative values for memcpy. Such a thing
hasn't occured to me: The prototype for the function specifies a size_t
argument, and size_t is supposed to be unsigned. This means, _afaik_, that a
negative value should be implicitly cast to a positive "equivalent". So, I
assume testing for this would be only useful as a way to show that (one of)
eglibc's implementation(s) doesn't obey sheer basics. However (not that this
isn't an eerie bug), I'm also a bit skeptical as to how a user-provided
value [+not stored in a size_t] would find itself in an argument to memcpy.
String.c is next after the alloc.c rewrite which is what I'm doing now (and
possibly after the task #7 which you suggested a while back), so if Rich
thinks this may be important to test for a reason unobvious to me, I guess I
can throw it in (though I'd have to use some non-size_t, sufficiently big
signed type to store test data :-/). In case of eglibc, I could have memcpy
jump to the same function used as the signal handler, and then it'd jump
back to a setjmp and we'd notice this behavior (that is, assuming the size
of the real argument type can be callculated for each platform). If I then
use the same setjmp/handler for a SIGSEGV, we could also catch other
hypothetical and only similarily buggy implementation behavior, and have
both report a same ambigous "negative argument" error message. But then I
guess the same applies to all other functions that should take a size_t or
any other positive type, doesn't it? :-/
Luka.
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