From: Marek Polacek <polacek@redhat.com>
To: "Joseph S. Myers" <joseph@codesourcery.com>
Cc: GCC Patches <gcc-patches@gcc.gnu.org>,
Jakub Jelinek <jakub@redhat.com>,
Jason Merrill <jason@redhat.com>
Subject: Re: [PATCH][ubsan] Add VLA bound instrumentation
Date: Thu, 12 Sep 2013 16:29:00 -0000 [thread overview]
Message-ID: <20130912161237.GP23899@redhat.com> (raw)
In-Reply-To: <Pine.LNX.4.64.1309121546080.5614@digraph.polyomino.org.uk>
On Thu, Sep 12, 2013 at 03:52:18PM +0000, Joseph S. Myers wrote:
> On Thu, 12 Sep 2013, Marek Polacek wrote:
>
> > This patch adds the instrumentation of VLA bounds. Basically, it just
> > checks that the size of a VLA is positive. I.e., We also issue an error
> > if the size of the VLA is 0. It catches e.g.
>
> This is not an objection to this patch, but there are a few other bits of
> VLA bound instrumentation that could be done as well. If the size has a
> wide-enough type to be bigger than the target's SIZE_MAX, and is indeed
> bigger than SIZE_MAX, that could be detected at runtime as well. Or if
> the multiplication of array size and element size exceeds SIZE_MAX (this
> covers both elements of constant size, and elements that are themselves
> VLAs, but the former can be handled more efficiently by comparing against
> an appropriate constant rather than needing a runtime test for whether a
> multiplication in size_t overflows).
>
> (Actually, I believe sizes (in bytes) greater than target PTRDIFF_MAX, not
> just SIZE_MAX, should be caught, because pointer subtraction cannot work
> reliably with larger objects. So it's not just when the size or
> multiplication overflow size_t, but when they overflow ptrdiff_t.)
Yup, this all sounds good. I'll look at this tomorrow. I think I'd
prefer doing this as a follow-up, after the C/C++ FE parts are
reviewed; doing SIZE_MAX/PTRDIFF_MAX checking then should require
changes only in c-ubsan.c.
Marek
next prev parent reply other threads:[~2013-09-12 16:12 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-09-12 12:38 Marek Polacek
2013-09-12 12:48 ` Marek Polacek
2013-09-12 16:12 ` Joseph S. Myers
2013-09-12 16:20 ` Joseph S. Myers
2013-09-12 17:15 ` Marek Polacek
2013-09-13 10:29 ` Marek Polacek
2013-09-13 11:23 ` Eric Botcazou
2013-09-13 18:01 ` Joseph S. Myers
2013-09-16 11:13 ` Marek Polacek
2013-09-16 13:39 ` Florian Weimer
2013-09-12 16:29 ` Marek Polacek [this message]
2013-09-25 13:23 ` Marek Polacek
2013-10-07 20:17 ` Marek Polacek
2013-10-15 13:25 ` Marek Polacek
2013-10-15 15:01 ` Joseph S. Myers
2013-10-24 20:35 ` Jason Merrill
2013-10-25 17:38 ` Marek Polacek
2013-10-25 19:04 ` Jason Merrill
2013-10-25 19:15 ` Marek Polacek
2013-10-25 19:30 ` Jason Merrill
2013-10-30 15:16 ` Marek Polacek
2013-10-30 16:08 ` Jason Merrill
2013-10-30 16:20 ` Marek Polacek
2013-10-30 20:55 ` Mike Stump
2013-10-30 22:46 ` Marek Polacek
2013-10-30 22:50 ` Mike Stump
2013-10-31 11:12 ` Marek Polacek
2013-10-31 3:18 ` Jason Merrill
2013-10-31 19:07 ` Marek Polacek
2013-11-01 17:35 ` Jason Merrill
2013-11-01 19:10 ` Marek Polacek
2013-11-01 20:39 ` Jason Merrill
2013-11-02 13:06 ` Marek Polacek
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