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Date: Wed, 26 Jan 2011 16:28:02 -0800
From: Kees Cook <kees.cook@canonical.com>
To: Joe Perches <joe@perches.com>
Cc: linux-kernel@vger.kernel.org, Rusty Russell <rusty@rustcorp.com.au>,
        Tejun Heo <tj@kernel.org>, Marcus Meissner <meissner@suse.de>,
        Jason Wessel <jason.wessel@windriver.com>,
        Eugene Teo <eugeneteo@kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Bjorn Helgaas <bjorn.helgaas@hp.com>, Len Brown <len.brown@intel.com>,
        Changli Gao <xiaosuo@gmail.com>,
        Dan Rosenberg <drosenberg@vsecurity.com>
Subject: Re: [PATCH] use %pK for /proc/kallsyms and /proc/modules
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 <1296087309.2448.33.camel@Joe-Laptop>
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On Wed, Jan 26, 2011 at 04:15:09PM -0800, Joe Perches wrote:
> On Tue, 2011-01-25 at 10:10 -0800, Kees Cook wrote:
> > Note that when compiling with -Wformat, these harmless warnings will
> > be emitted, and can be ignored:
> >   warning: '0' flag used with ‘%p’ gnu_printf format
> 
> > diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c
> []
> > @@ -477,11 +477,11 @@ static int s_show(struct seq_file *m, void *p)
> >  		 */
> >  		type = iter->exported ? toupper(iter->type) :
> >  					tolower(iter->type);
> > -		seq_printf(m, "%0*lx %c %s\t[%s]\n",
> > +		seq_printf(m, "%0*pK %c %s\t[%s]\n",
> >  			   (int)(2 * sizeof(void *)),
> >  			   iter->value, type, iter->name, iter->module_name);
> 
> You can change this to
> 
> 		seq_printf(m, "%pK %c %s\t[%s]\n",
>   			   iter->value, type, iter->name, iter->module_name);
> 
> as that's the normal size.
> 
> Presto.  No warnings.  Same output.

Ah-ha! I was comparing against POSIX %p, which doesn't zeropad. The
kernel's %p does, so that's perfect! Yay, no warnings. Thanks! I'll send an
updated patch.

-- 
Kees Cook
Ubuntu Security Team