linux-kernel - Re: [RFC v3 2/2] firmware: add firmware signature checking support

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Message-ID: <20150714192015.GO7021@wotan.suse.de>
Date:	Tue, 14 Jul 2015 21:20:15 +0200
From:	"Luis R. Rodriguez" <mcgrof@...e.com>
To:	Kees Cook <keescook@...omium.org>,
	David Howells <dhowells@...hat.com>
Cc:	"Luis R. Rodriguez" <mcgrof@...not-panic.com>,
	Ming Lei <ming.lei@...onical.com>, seth.forshee@...onical.com,
	Rusty Russell <rusty@...tcorp.com.au>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	David Howells <dhowells@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Paul Bolle <pebolle@...cali.nl>,
	linux-wireless <linux-wireless@...r.kernel.org>,
	Greg KH <gregkh@...uxfoundation.org>, jlee@...e.com,
	Takashi Iwai <tiwai@...e.de>,
	Casey Schaufler <casey@...aufler-ca.com>,
	Matthew Garrett <mjg59@...f.ucam.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Kyle McMartin <kyle@...nel.org>,
	David Woodhouse <David.Woodhouse@...el.com>
Subject: Re: [RFC v3 2/2] firmware: add firmware signature checking support

On Mon, Jun 08, 2015 at 12:56:44PM -0700, Kees Cook wrote:
> On Mon, May 18, 2015 at 5:45 PM, Luis R. Rodriguez
> <mcgrof@...not-panic.com> wrote:
> > From: "Luis R. Rodriguez" <mcgrof@...e.com>
> >
> > diff --git a/drivers/base/firmware_class.c b/drivers/base/firmware_class.c
> > index 134dd77..97cab65 100644
> > --- a/drivers/base/firmware_class.c
> > +++ b/drivers/base/firmware_class.c
> > @@ -180,17 +190,33 @@ static struct firmware_buf *__allocate_fw_buf(const char *fw_name,
> >                                               struct firmware_cache *fwc)
> >  {
> >         struct firmware_buf *buf;
> > +       const char *sign_ext = ".p7s";
> > +       char *signed_name;
> > +
> > +       signed_name = kzalloc(PATH_MAX, GFP_ATOMIC);
> > +       if (!signed_name)
> > +               return NULL;
> >
> >         buf = kzalloc(sizeof(*buf), GFP_ATOMIC);
> > -       if (!buf)
> > +       if (!buf) {
> > +               kfree(signed_name);
> >                 return NULL;
> > +       }
> >
> >         buf->fw_id = kstrdup_const(fw_name, GFP_ATOMIC);
> >         if (!buf->fw_id) {
> > +               kfree(signed_name);
> >                 kfree(buf);
> >                 return NULL;
> >         }
> >
> > +       strcpy(signed_name, buf->fw_id);
> > +       strncat(signed_name, sign_ext, strlen(sign_ext));
> 
> fw_id is potentially unbounded, so using strncat hear poses an
> overflow risk. Maybe better to use strlcpy?
> 

Thanks for the feedback, indeed.

 Luis
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