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

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Date:	Tue, 06 Nov 2012 08:03:16 +0100
From:	Takashi Iwai <tiwai@...e.de>
To:	Ming Lei <tom.leiming@...il.com>
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

At Tue, 6 Nov 2012 10:30:26 +0800,
Ming Lei wrote:
> 
> On Tue, Nov 6, 2012 at 1:18 AM, Takashi Iwai <tiwai@...e.de> wrote:
> >
> > To be noted, it doesn't support the firmwares via udev but only the
> > direct loading, and the check for built-in firmware is missing, too.
> 
> Generally, both direct loading and udev may request one same firmware
> image. And after check failed, current firmware load will fallback on udev
> to complete loading, so looks a check-failed firmware still can be loaded
> into kernel no matter if there is firmware signature check or not.

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