linux-kernel - Re: [PATCH RFC] selinux: provide _

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Message-ID: <CAHC9VhRPZKHt7EoK=O2keuyMm=fYyEAbWjJTG0uFA_Z6o_0-3A@mail.gmail.com>
Date:   Tue, 21 May 2019 16:23:01 -0400
From:   Paul Moore <paul@...l-moore.com>
To:     Nicholas Mc Guire <der.herr@...r.at>
Cc:     Nicholas Mc Guire <hofrat@...dl.org>,
        Stephen Smalley <sds@...ho.nsa.gov>,
        Eric Paris <eparis@...isplace.org>,
        peter enderborg <peter.enderborg@...y.com>,
        selinux@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH RFC] selinux: provide __le variables explicitly

On Thu, May 9, 2019 at 3:40 PM Paul Moore <paul@...l-moore.com> wrote:
> On Wed, May 8, 2019 at 8:14 PM Nicholas Mc Guire <der.herr@...r.at> wrote:
> > On Wed, May 08, 2019 at 05:47:32PM -0400, Paul Moore wrote:
> > > On Wed, May 8, 2019 at 2:27 AM Nicholas Mc Guire <hofrat@...dl.org> wrote:
> > > > While the endiannes is being handled properly sparse was unable to verify
> > > > this due to type inconsistency. So introduce an additional __le32
> > > > respectively _le64 variable to be passed to le32/64_to_cpu() to allow
> > > > sparse to verify proper typing. Note that this patch does not change
> > > > the generated binary on little-endian systems - on 32bit powerpc it
> > > > does change the binary.
> > > >
> > > > Signed-off-by: Nicholas Mc Guire <hofrat@...dl.org>
> > > > ---
> > > >
> > > > Problem located by an experimental coccinelle script to locate
> > > > patters that make sparse unhappy (false positives):
> > > >
> > > > sparse complaints on different architectures fixed by this patch are:
> > > >
> > > > ppc6xx_defconfig
> > > >   CHECK   security/selinux/ss/ebitmap.c
> > > > security/selinux/ss/ebitmap.c:389:28: warning: cast to restricted __le32
> > > > security/selinux/ss/ebitmap.c:389:28: warning: cast to restricted __le32
> > > > security/selinux/ss/ebitmap.c:389:28: warning: cast to restricted __le32
> > > > security/selinux/ss/ebitmap.c:389:28: warning: cast to restricted __le32
> > > > security/selinux/ss/ebitmap.c:389:28: warning: cast to restricted __le32
> > > > security/selinux/ss/ebitmap.c:389:28: warning: cast to restricted __le32
> > > > security/selinux/ss/ebitmap.c:431:23: warning: cast to restricted __le64
> > > > security/selinux/ss/ebitmap.c:431:23: warning: cast to restricted __le64
> > > > security/selinux/ss/ebitmap.c:431:23: warning: cast to restricted __le64
> > > > security/selinux/ss/ebitmap.c:431:23: warning: cast to restricted __le64
> > > > security/selinux/ss/ebitmap.c:431:23: warning: cast to restricted __le64
> > > > security/selinux/ss/ebitmap.c:431:23: warning: cast to restricted __le64
> > > > security/selinux/ss/ebitmap.c:431:23: warning: cast to restricted __le64
> > > > security/selinux/ss/ebitmap.c:431:23: warning: cast to restricted __le64
> > > > security/selinux/ss/ebitmap.c:431:23: warning: cast to restricted __le64
> > > > security/selinux/ss/ebitmap.c:431:23: warning: cast to restricted __le64
> > > >
> > > > Little-endian systems:
> > > >
> > > > loongson3_defconfig
> > > > security/selinux/ss/ebitmap.c:389:28: warning: cast to restricted __le32
> > > > security/selinux/ss/ebitmap.c:431:23: warning: cast to restricted __le64
> > > >
> > > > x86_64_defconfig
> > > > security/selinux/ss/ebitmap.c:389:28: warning: cast to restricted __le32
> > > > security/selinux/ss/ebitmap.c:431:23: warning: cast to restricted __le64
> > > >
> > > > Patch was compile-tested with: x86_64_defconfig,loongson3_defconfig (both
> > > > little-endian) and ppc603_defconfig (big-endian).
> > > >
> > > > On little-endian systems the patch has no impact on the generated binary
> > > > (which is expected) but on the 32bit powerpc it does change the binary
> > > > which is not expected but since I'm not able to generate the .lst files
> > > > in security/selinux/ss/ due to the lack of a Makefile it is not clear
> > > > if this is an unexpected side-effect or due only to the introduction of
> > > > the additional variables. From my understanding the patch does not change
> > > > the program logic so if the code was correct on big-endian systems before
> > > > it should still be correct now.
> > >
> > > This is a bit worrisome, but I tend to agree that this patch *should*
> > > be correct.  I'm thinking you're probably right in that the resulting
> > > binary difference could be due to the extra variable.  Have you tried
> > > any other big-endian arches?
> > >
> >
> > just tried ppc64_defconfig + AUDIT=y, SECURITY=y, SECURITY_NETWORK=y, SECURITY_SELINUX=y
> >
> > sparse will complain in the original version about:
> >   CHECK   security/selinux/ss/ebitmap.c
> > security/selinux/ss/ebitmap.c:389:28: warning: cast to restricted __le32
> > security/selinux/ss/ebitmap.c:389:28: warning: cast to restricted __le32
> > security/selinux/ss/ebitmap.c:389:28: warning: cast to restricted __le32
> > security/selinux/ss/ebitmap.c:389:28: warning: cast to restricted __le32
> > security/selinux/ss/ebitmap.c:389:28: warning: cast to restricted __le32
> > security/selinux/ss/ebitmap.c:389:28: warning: cast to restricted __le32
> > security/selinux/ss/ebitmap.c:431:23: warning: cast to restricted __le64
> > security/selinux/ss/ebitmap.c:431:23: warning: cast to restricted __le64
> > security/selinux/ss/ebitmap.c:431:23: warning: cast to restricted __le64
> > security/selinux/ss/ebitmap.c:431:23: warning: cast to restricted __le64
> > security/selinux/ss/ebitmap.c:431:23: warning: cast to restricted __le64
> > security/selinux/ss/ebitmap.c:431:23: warning: cast to restricted __le64
> > security/selinux/ss/ebitmap.c:431:23: warning: cast to restricted __le64
> > security/selinux/ss/ebitmap.c:431:23: warning: cast to restricted __le64
> > security/selinux/ss/ebitmap.c:431:23: warning: cast to restricted __le64
> > security/selinux/ss/ebitmap.c:431:23: warning: cast to restricted __le64
> >
> > which is the same as 32bit ppc - after the patch is applied that is resolved
> > and and the generated ebitmap.o files are binary identical.
> >
> > I just had chosen ppc6xx_defconfig as my big-endian test-target as SELINUX
> > was on there by default so I assumed it would be the most reasonable
> > compile-test target.
>
> Thanks.
>
> I think this is probably safe to merge once the merge window closes.

... and that time is now; merged into selinux/next.  Thanks.

/me crosses his fingers on this one

-- 
paul moore
www.paul-moore.com