From: Mimi Zohar <zohar@linux.vnet.ibm.com>
To: Hans de Goede <hdegoede@redhat.com>,
Ard Biesheuvel <ard.biesheuvel@linaro.org>,
"Luis R . Rodriguez" <mcgrof@kernel.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, "H . Peter Anvin" <hpa@zytor.com>
Cc: Peter Jones <pjones@redhat.com>, Dave Olsthoorn <dave@bewaar.me>,
Will Deacon <will.deacon@arm.com>,
Andy Lutomirski <luto@kernel.org>,
Matt Fleming <matt@codeblueprint.co.uk>,
David Howells <dhowells@redhat.com>,
Josh Triplett <josh@joshtriplett.org>,
dmitry.torokhov@gmail.com, mfuzzey@parkeon.com,
Kalle Valo <kvalo@codeaurora.org>,
Arend Van Spriel <arend.vanspriel@broadcom.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
nbroeking@me.com, bjorn.andersson@linaro.org,
Torsten Duwe <duwe@suse.de>, Kees Cook <keescook@chromium.org>,
x86@kernel.org, linux-efi@vger.kernel.org,
linux-kernel@vger.kernel.org,
linux-security-module <linux-security-module@vger.kernel.org>
Subject: Re: [PATCH v5 2/5] efi: Add embedded peripheral firmware support
Date: Tue, 01 May 2018 15:27:27 -0400 [thread overview]
Message-ID: <1525202847.5669.64.camel@linux.vnet.ibm.com> (raw)
In-Reply-To: <dc122066-9973-a1be-3456-6d6181a8fc9f@redhat.com>
On Tue, 2018-05-01 at 21:11 +0200, Hans de Goede wrote:
> Hi,
>
> On 01-05-18 16:36, Mimi Zohar wrote:
> > [Cc'ing linux-security]
> >
> > On Sun, 2018-04-29 at 11:35 +0200, Hans de Goede wrote:
> > [...]
> >> diff --git a/drivers/base/firmware_loader/fallback_efi.c b/drivers/base/firmware_loader/fallback_efi.c
> >> new file mode 100644
> >> index 000000000000..82ba82f48a79
> >> --- /dev/null
> >> +++ b/drivers/base/firmware_loader/fallback_efi.c
> >> @@ -0,0 +1,51 @@
> >> +// SPDX-License-Identifier: GPL-2.0
> >> +
> >> +#include <linux/efi_embedded_fw.h>
> >> +#include <linux/property.h>
> >> +#include <linux/security.h>
> >> +#include <linux/vmalloc.h>
> >> +
> >> +#include "fallback.h"
> >> +#include "firmware.h"
> >> +
> >> +int fw_get_efi_embedded_fw(struct device *dev, struct fw_priv *fw_priv,
> >> + enum fw_opt *opt_flags, int ret)
> >> +{
> >> + enum kernel_read_file_id id = READING_FIRMWARE;
> >
> > Please define a new kernel_read_file_id for this (eg.
> > READING_FIRMWARE_EFI_EMBEDDED).
>
> Are you sure, I wonder how useful it is to add a new
> kernel_read_file_id every time a new way to get firmware
> comes up?
>
> I especially wonder about the sense in adding a new id
> given that the quite old FIRMWARE_PREALLOC_BUFFER is
> still not supported / checked properly by the security code.
I posted patches earlier today[1], which address this. Patch 5/6 just
makes it equivalent to READING_FIRMWARE. Patch 6/6 questions whether
the device has access to the pre-allocated buffer *before* the
signature has been verified.
[1] kernsec.org/pipermail/linux-security-module-archive/2018-May/006639.html
>
> Anyways I can add a new id if you want me to, what about
> when fw_get_efi_embedded_fw is reading into a driver allocated
> buffer, do you want a separate EADING_FIRMWARE_EFI_EMBEDDED_PREALLOC_BUFFER
> for that ?
Without the kernel being able to verify the firmware's signature, I'm
not sure it makes much of a difference.
>
> >
> >> + size_t size, max = INT_MAX;
> >> + int rc;
> >> +
> >> + if (!dev)
> >> + return ret;
> >> +
> >> + if (!device_property_read_bool(dev, "efi-embedded-firmware"))
> >> + return ret;
> >
> > Instead of calling security_kernel_post_read_file(), either in
> > device_property_read_bool() or here call security_kernel_read_file().
> >
> > The pre read call is for deciding whether to allow this call
> > independent of the firmware being loaded, whereas the post security
> > call is currently being used by IMA-appraisal for verifying a
> > signature. There might be other LSMs using the post hook as well. As
> > there is no kernel signature associated with this firmware, use the
> > security pre read_file hook.
>
> Only the pre hook? I believe the post-hook should still be called too,
> right? So that we've hashes of all loaded firmwares in the IMA core.
Good catch! Right, if IMA-measurement is enabled, then we would want
to add the measurement.
Mimi
next prev parent reply other threads:[~2018-05-01 19:27 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-04-29 9:35 [PATCH v5 0/5] efi/firmware/platform-x86: Add EFI embedded fw support Hans de Goede
2018-04-29 9:35 ` [PATCH v5 1/5] efi: Export boot-services code and data as debugfs-blobs Hans de Goede
2018-04-29 9:35 ` [PATCH v5 2/5] efi: Add embedded peripheral firmware support Hans de Goede
2018-05-01 14:36 ` Mimi Zohar
2018-05-01 19:11 ` Hans de Goede
2018-05-01 19:27 ` Mimi Zohar [this message]
2018-05-03 22:23 ` Luis R. Rodriguez
2018-05-03 23:02 ` Mimi Zohar
2018-05-01 19:29 ` Andy Lutomirski
2018-05-01 20:06 ` Lukas Wunner
2018-05-02 14:49 ` Hans de Goede
2018-05-03 22:31 ` Luis R. Rodriguez
2018-05-03 22:35 ` Andy Lutomirski
2018-05-13 11:41 ` Hans de Goede
2018-05-13 11:05 ` Hans de Goede
2018-05-03 23:29 ` Luis R. Rodriguez
2018-05-04 5:54 ` Ard Biesheuvel
2018-05-08 17:12 ` Luis R. Rodriguez
2018-05-13 14:10 ` Hans de Goede
2018-05-04 5:56 ` Ard Biesheuvel
2018-05-13 11:03 ` Hans de Goede
2018-05-13 11:43 ` Ard Biesheuvel
2018-05-13 13:26 ` Hans de Goede
2018-04-29 9:35 ` [PATCH v5 3/5] platform/x86: Rename silead_dmi to touchscreen_dmi Hans de Goede
2018-04-29 9:35 ` [PATCH v5 4/5] platform/x86: touchscreen_dmi: Add EFI embedded firmware info support Hans de Goede
2018-04-29 9:35 ` [PATCH v5 5/5] platform/x86: touchscreen_dmi: Add info for the Chuwi Vi8 Plus tablet Hans de Goede
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