linux-kernel - Re: [PATCH RFC 0/4] Add firmware signature file check

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Message-ID: <CACVXFVPDZnXshvartbTt6gaGzcb+03sVq3Qm3apQQ8AVcQWerg@mail.gmail.com>
Date:	Tue, 6 Nov 2012 15:16:43 +0800
From:	Ming Lei <tom.leiming@...il.com>
To:	Takashi Iwai <tiwai@...e.de>
Cc:	Matthew Garrett <mjg59@...f.ucam.org>,
	Alan Cox <alan@...rguk.ukuu.org.uk>, joeyli <jlee@...e.com>,
	Jiri Kosina <jkosina@...e.cz>,
	David Howells <dhowells@...hat.com>,
	Rusty Russell <rusty@...tcorp.com.au>,
	linux-kernel@...r.kernel.org,
	linux-security-module@...r.kernel.org, linux-efi@...r.kernel.org
Subject: Re: [PATCH RFC 0/4] Add firmware signature file check

On Tue, Nov 6, 2012 at 3:03 PM, Takashi Iwai <tiwai@...e.de> wrote:
>
> Yeah, it's just uncovered in the patch.  As a easy solution, apply the
> patch like below to disallow the udev fw loading when signature check
> is enforced.
>
>
> thanks,
>
> Takashi
>
> ---
> diff --git a/drivers/base/firmware_class.c b/drivers/base/firmware_class.c
> index 575bc4c..93121c3 100644
> --- a/drivers/base/firmware_class.c
> +++ b/drivers/base/firmware_class.c
> @@ -912,6 +912,13 @@ static int _request_firmware_load(struct firmware_priv *fw_priv, bool uevent,
>                 goto handle_fw;
>         }
>
> +       /* signature check isn't handled via udev fw loading */
> +       if (sig_enforce) {
> +               fw_load_abort(fw_priv);
> +               direct_load = 1;
> +               goto handle_fw;
> +       }
> +

The above might be wrong if the firmware file doesn't exist in default
search paths. You should skip loading from user space only if
verify_signature() returns false. And the udev loading should be
resorted to if there is no such firmware file in default search paths.

>         /* fall back on userspace loading */
>         buf->fmt = PAGE_BUF;
>


Thanks,
-- 
Ming Lei
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