linux-kernel - Re: [PATCH RFC v2 5/22] selinux: avoid nontransitive comparison

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAJ2a_Dei0Bg14N2E9U2FzM0OEvEQbOcTvQ76FH4Ut6JYq5VybA@mail.gmail.com>
Date: Wed, 8 Jan 2025 14:17:15 +0100
From: Christian Göttsche <cgzones@...glemail.com>
To: Paul Moore <paul@...l-moore.com>
Cc: Christian Göttsche <cgoettsche@...tendoof.de>, 
	selinux@...r.kernel.org, Stephen Smalley <stephen.smalley.work@...il.com>, 
	Ondrej Mosnacek <omosnace@...hat.com>, Nathan Chancellor <nathan@...nel.org>, 
	Nick Desaulniers <ndesaulniers@...gle.com>, Bill Wendling <morbo@...gle.com>, 
	Justin Stitt <justinstitt@...gle.com>, Thiébaud Weksteen <tweek@...gle.com>, 
	Bram Bonné <brambonne@...gle.com>, 
	Masahiro Yamada <masahiroy@...nel.org>, linux-kernel@...r.kernel.org, llvm@...ts.linux.dev
Subject: Re: [PATCH RFC v2 5/22] selinux: avoid nontransitive comparison

On Wed, 8 Jan 2025 at 04:00, Paul Moore <paul@...l-moore.com> wrote:
>
> On Dec 16, 2024 =?UTF-8?q?Christian=20G=C3=B6ttsche?= <cgoettsche@...tendoof.de> wrote:
> >
> > Avoid using nontransitive comparison to prevent unexpected sorting
> > results due to (well-defined) overflows.
> > See https://www.qualys.com/2024/01/30/qsort.txt for a related issue in
> > glibc's qsort(3).
> >
> > Signed-off-by: Christian Göttsche <cgzones@...glemail.com>
> > ---
> >  security/selinux/ss/policydb.c | 18 ++++++++++--------
> >  1 file changed, 10 insertions(+), 8 deletions(-)
> >
> > diff --git a/security/selinux/ss/policydb.c b/security/selinux/ss/policydb.c
> > index 3ba5506a3fff..eb944582d7a6 100644
> > --- a/security/selinux/ss/policydb.c
> > +++ b/security/selinux/ss/policydb.c
> > @@ -37,6 +37,8 @@
> >  #include "mls.h"
> >  #include "services.h"
> >
> > +#define spaceship_cmp(a, b) (((a) > (b)) - ((a) < (b)))
>
> I'll admit that it took me a while to figure out why you decided to
> name this macro "spaceship_cmp", and then I had a little laugh when
> I realized why it was called the "spaceship" operator :)
>
> Anyway, while the spaceship operator is likely familiar to people who
> have a Perl background, the kernel is still mostly a C project so I
> don't think we can expect a base understanding of Perl, especially
> these days as Perl isn't as popular as in the past.  Can we rename
> this to something else that makes more sense in the context of C?

There seem to be 4 similar macros already in the kernel, 3 named
cmp_int() and one instance named cmp_ptr().
So I am going with cmp_int() in v3 for now, but I am open for other suggestions.

>
> --
> paul-moore.com