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To:     "H. Peter Anvin" <hpa@zytor.com>,
        Al Viro <viro@zeniv.linux.org.uk>,
        Arnd Bergmann <arnd@arndb.de>,
        James McMechan <james.w.mcmechan@gmail.com>,
        Jonathan Corbet <corbet@lwn.net>,
        Mimi Zohar <zohar@linux.vnet.ibm.com>,
        Rob Landley <rob@landley.net>
From:   Taras Kondratiuk <takondra@cisco.com>
In-Reply-To: <b3451193-0666-d929-01f3-29d3872bd5d4@landley.net>
Cc:     initramfs@vger.kernel.org, Victor Kamensky <kamensky@cisco.com>,
        linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-security-module@vger.kernel.org, xe-linux-external@cisco.com
References: <1516850875-25066-1-git-send-email-takondra@cisco.com>
 <1516850875-25066-12-git-send-email-takondra@cisco.com>
 <b3451193-0666-d929-01f3-29d3872bd5d4@landley.net>
Message-ID: <151699903485.21956.15795523878472133751@takondra-t460s>
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Subject: Re: [PATCH v2 11/15] gen_init_cpio: add newcx format
Date:   Fri, 26 Jan 2018 12:37:14 -0800
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

Quoting Rob Landley (2018-01-25 18:40:25)
> On 01/24/2018 09:27 PM, Taras Kondratiuk wrote:
> > diff --git a/usr/gen_init_cpio.c b/usr/gen_init_cpio.c
> > index 7a2a6d85345d..78a47a5bdcb1 100644
> > --- a/usr/gen_init_cpio.c
> > +++ b/usr/gen_init_cpio.c
> > @@ -10,6 +10,7 @@
> >  #include <errno.h>
> >  #include <ctype.h>
> >  #include <limits.h>
> > +#include <assert.h>
> =

> You're adding an assert? Really?
> =

> >       fputs(s, stdout);
> > -     offset +=3D 110;
> > +     assert((offset & 3) =3D=3D 0);
> > +     offset +=3D cpio_hdr_size;
> =

> Why?

Current code assumes that previous file entry in cpio is padded to 4
byte boundary. The assert just captures this assumption. It should be
true unless there is a bug in the code and some padding is missing.

Actually this assert should be a part of the next patch (#12) that
modifies padding code.