Linux-Integrity Archive on lore.kernel.org
 help / color / Atom feed
From: Nick Desaulniers <ndesaulniers@google.com>
To: denkenz@gmail.com
Cc: jejb@linux.ibm.com, dhowells@redhat.com,
	Nathan Chancellor <natechancellor@gmail.com>,
	Eric Biggers <ebiggers@google.com>,
	zohar@linux.vnet.ibm.com, jmorris@namei.org, serge@hallyn.com,
	linux-integrity@vger.kernel.org, keyrings@vger.kernel.org,
	linux-security-module@vger.kernel.org,
	LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] KEYS: trusted: fix -Wvarags warning
Date: Fri, 12 Oct 2018 10:17:50 -0700
Message-ID: <CAKwvOdnRJtHEUf-2kObUiUCc_ZPRdYHxMft3s1YE6=9EnHYMMg@mail.gmail.com> (raw)
In-Reply-To: <CAKwvOdmStDm3Lz=W7XjmB7f7ihe4hLOmaBRLOrStbkBMRKwdjA@mail.gmail.com>

On Fri, Oct 12, 2018 at 10:05 AM Nick Desaulniers
<ndesaulniers@google.com> wrote:
>
> On Fri, Oct 12, 2018 at 8:14 AM Denis Kenzior <denkenz@gmail.com> wrote:
> >
> > Hi James,
> >
> > >> So can't we simply use 'bool' or uint32 as the type for h3 instead
> > >> of re-ordering everything
> > >
> > > The problem is the standard is ambiguious.  The only thing that's
> > > guaranteed to work for all time is a char *.  If you want to keep the
> > > order, what I'd suggest is inserting a dummy pointer argument which is
> > > always expected to be NULL between the h3 and the varargs.
> >
> > So maybe I'm misunderstanding something, but the issue seems to be that
> > unsigned char is promoted to 'unsigned char *' by Clang and probably
> > unsigned int or int by gcc.
>
> No. This is extremely well defined behavior in C.  In C, integral
> types are NEVER promoted to pointer to integer types, only to larger
> integral types through rules more complicated than the correct flags
> to pass to `tar`.
> https://xkcd.com/1168/

And may have their signedness converted.
https://wiki.sei.cmu.edu/confluence/display/c/INT02-C.+Understand+integer+conversion+rules
is the reference I use, though I always feel like there's quite a bit
of mental gymnastics involved interpreting it.

>
> >
> > So instead of having unsigned char h3, can't we simply have bool h3 or
> > unsigned int h3?
>
> int is the default argument promotion. Proposed:
> https://github.com/ClangBuiltLinux/linux/issues/41#issuecomment-428365339
>
> >
> > Regards,
> > -Denis
> >
>
>
> --
> Thanks,
> ~Nick Desaulniers



-- 
Thanks,
~Nick Desaulniers

  reply index

Thread overview: 35+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-10-09 22:11 undefined behavior (-Wvarargs) in security/keys/trusted.c#TSS_authhmac() Nick Desaulniers
2018-10-11 16:02 ` Arnd Bergmann
2018-10-11 16:10   ` James Bottomley
2018-10-11 20:31     ` [PATCH] KEYS: trusted: fix -Wvarags warning ndesaulniers
2018-10-12  1:50       ` Nathan Chancellor
2018-10-12 16:55         ` Nick Desaulniers
2018-10-12 17:03           ` Nathan Chancellor
2018-10-12 12:29       ` Denis Kenzior
2018-10-12 15:05         ` James Bottomley
2018-10-12 15:13           ` Denis Kenzior
2018-10-12 15:22             ` James Bottomley
2018-10-12 15:44               ` Denis Kenzior
2018-10-12 15:46                 ` James Bottomley
2018-10-12 15:53                   ` Denis Kenzior
2018-10-12 16:01                     ` James Bottomley
2018-10-12 17:14                       ` Nick Desaulniers
2018-10-12 15:25             ` James Bottomley
2018-10-12 17:05             ` Nick Desaulniers
2018-10-12 17:17               ` Nick Desaulniers [this message]
2018-10-12 17:27               ` Denis Kenzior
2018-10-12 18:39                 ` Nick Desaulniers
2018-10-12 17:02         ` Nick Desaulniers
2018-10-12 17:15           ` Denis Kenzior
2018-10-15  9:26       ` David Laight
2018-10-15  9:26         ` David Laight
2018-10-15 21:53         ` Nick Desaulniers
2018-10-16  8:13           ` David Laight
2018-10-16  8:13             ` David Laight
2018-10-22 23:43             ` [PATCH v2] " ndesaulniers
2018-10-23  0:00               ` Nathan Chancellor
2018-10-24  8:36               ` Jarkko Sakkinen
2018-10-29 17:54                 ` Nick Desaulniers
2019-02-11 18:36                   ` Nick Desaulniers
2019-02-12 23:12                     ` Jarkko Sakkinen
2019-02-14 10:52                       ` Jarkko Sakkinen

Reply instructions:

You may reply publically 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='CAKwvOdnRJtHEUf-2kObUiUCc_ZPRdYHxMft3s1YE6=9EnHYMMg@mail.gmail.com' \
    --to=ndesaulniers@google.com \
    --cc=denkenz@gmail.com \
    --cc=dhowells@redhat.com \
    --cc=ebiggers@google.com \
    --cc=jejb@linux.ibm.com \
    --cc=jmorris@namei.org \
    --cc=keyrings@vger.kernel.org \
    --cc=linux-integrity@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-security-module@vger.kernel.org \
    --cc=natechancellor@gmail.com \
    --cc=serge@hallyn.com \
    --cc=zohar@linux.vnet.ibm.com \
    /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

Linux-Integrity Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linux-integrity/0 linux-integrity/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-integrity linux-integrity/ https://lore.kernel.org/linux-integrity \
		linux-integrity@vger.kernel.org linux-integrity@archiver.kernel.org
	public-inbox-index linux-integrity


Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.linux-integrity


AGPL code for this site: git clone https://public-inbox.org/ public-inbox