LKML Archive on lore.kernel.org
help / color / mirror / Atom feed
From: Paul Moore <paul@paul-moore.com>
To: Nicholas Mc Guire <hofrat@osadl.org>
Cc: Stephen Smalley <sds@tycho.nsa.gov>,
	Eric Paris <eparis@parisplace.org>,
	peter enderborg <peter.enderborg@sony.com>,
	selinux@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH RFC] selinux: provide __le variables explicitly
Date: Wed, 8 May 2019 17:47:32 -0400	[thread overview]
Message-ID: <CAHC9VhSU7pzWby78gHkYKm3t1LopSCoHBfmp=uBc+mF234K8mg@mail.gmail.com> (raw)
In-Reply-To: <1557296477-4694-1-git-send-email-hofrat@osadl.org>

On Wed, May 8, 2019 at 2:27 AM Nicholas Mc Guire <hofrat@osadl.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@osadl.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?

> Patch is against 5.1 (localversion-next is next-20190506)
>
>  security/selinux/ss/ebitmap.c | 10 ++++++----
>  1 file changed, 6 insertions(+), 4 deletions(-)
>
> diff --git a/security/selinux/ss/ebitmap.c b/security/selinux/ss/ebitmap.c
> index 8f624f8..09929fc 100644
> --- a/security/selinux/ss/ebitmap.c
> +++ b/security/selinux/ss/ebitmap.c
> @@ -347,7 +347,9 @@ int ebitmap_read(struct ebitmap *e, void *fp)
>  {
>         struct ebitmap_node *n = NULL;
>         u32 mapunit, count, startbit, index;
> +       __le32 ebitmap_start;
>         u64 map;
> +       __le64 mapbits;
>         __le32 buf[3];
>         int rc, i;
>
> @@ -381,12 +383,12 @@ int ebitmap_read(struct ebitmap *e, void *fp)
>                 goto bad;
>
>         for (i = 0; i < count; i++) {
> -               rc = next_entry(&startbit, fp, sizeof(u32));
> +               rc = next_entry(&ebitmap_start, fp, sizeof(u32));
>                 if (rc < 0) {
>                         pr_err("SELinux: ebitmap: truncated map\n");
>                         goto bad;
>                 }
> -               startbit = le32_to_cpu(startbit);
> +               startbit = le32_to_cpu(ebitmap_start);
>
>                 if (startbit & (mapunit - 1)) {
>                         pr_err("SELinux: ebitmap start bit (%d) is "
> @@ -423,12 +425,12 @@ int ebitmap_read(struct ebitmap *e, void *fp)
>                         goto bad;
>                 }
>
> -               rc = next_entry(&map, fp, sizeof(u64));
> +               rc = next_entry(&mapbits, fp, sizeof(u64));
>                 if (rc < 0) {
>                         pr_err("SELinux: ebitmap: truncated map\n");
>                         goto bad;
>                 }
> -               map = le64_to_cpu(map);
> +               map = le64_to_cpu(mapbits);
>
>                 index = (startbit - n->startbit) / EBITMAP_UNIT_SIZE;
>                 while (map) {
> --
> 2.1.4
>


-- 
paul moore
www.paul-moore.com

  reply	other threads:[~2019-05-08 21:47 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-08  6:21 Nicholas Mc Guire
2019-05-08 21:47 ` Paul Moore [this message]
2019-05-09  0:13   ` Nicholas Mc Guire
2019-05-09 19:40     ` Paul Moore
2019-05-21 20:23       ` Paul Moore

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to='CAHC9VhSU7pzWby78gHkYKm3t1LopSCoHBfmp=uBc+mF234K8mg@mail.gmail.com' \
    --to=paul@paul-moore.com \
    --cc=eparis@parisplace.org \
    --cc=hofrat@osadl.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=peter.enderborg@sony.com \
    --cc=sds@tycho.nsa.gov \
    --cc=selinux@vger.kernel.org \
    --subject='Re: [PATCH RFC] selinux: provide __le variables explicitly' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).