linux-kernel - Re: [PATCH v2 11/15] gen_init

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Date:   Fri, 26 Jan 2018 12:37:14 -0800
From:   Taras Kondratiuk <takondra@...co.com>
To:     "H. Peter Anvin" <hpa@...or.com>,
        Al Viro <viro@...iv.linux.org.uk>,
        Arnd Bergmann <arnd@...db.de>,
        James McMechan <james.w.mcmechan@...il.com>,
        Jonathan Corbet <corbet@....net>,
        Mimi Zohar <zohar@...ux.vnet.ibm.com>,
        Rob Landley <rob@...dley.net>
Cc:     initramfs@...r.kernel.org, Victor Kamensky <kamensky@...co.com>,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-security-module@...r.kernel.org, xe-linux-external@...co.com
Subject: Re: [PATCH v2 11/15] gen_init_cpio: add newcx format

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 += 110;
> > +     assert((offset & 3) == 0);
> > +     offset += 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.