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From: Hans de Goede <hdegoede@redhat.com>
To: "Luis R. Rodriguez" <mcgrof@kernel.org>,
	Mimi Zohar <zohar@linux.vnet.ibm.com>,
	Kees Cook <keescook@chromium.org>
Cc: Darren Hart <dvhart@infradead.org>,
	Andy Shevchenko <andy@infradead.org>,
	Ard Biesheuvel <ard.biesheuvel@linaro.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, "H . Peter Anvin" <hpa@zytor.com>,
	platform-driver-x86@vger.kernel.org,
	linux-kernel@vger.kernel.org, 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>,
	x86@kernel.org, linux-efi@vger.kernel.org
Subject: Re: [PATCH v3 2/5] efi: Add embedded peripheral firmware support
Date: Tue, 24 Apr 2018 17:09:52 +0200	[thread overview]
Message-ID: <71e6a45a-398d-b7a4-dab0-8b9936683226@redhat.com> (raw)
In-Reply-To: <20180423211143.GZ14440@wotan.suse.de>

Hi,

On 23-04-18 23:11, Luis R. Rodriguez wrote:
> Hans, please see use of READING_FIRMWARE_PREALLOC_BUFFER, we'll need a new ID
> and security for this type of request so IMA can reject it if the policy is
> configured for it.

Hmm, interesting, actually it seems like the whole existence
of READING_FIRMWARE_PREALLOC_BUFFER is a mistake, the IMA
framework really does not care if we are loading the firmware
into memory allocated by the firmware-loader code, or into
memory allocated by the device-driver requesting the firmware.

As such the current IMA code (from v4.17-rc2) actually does
not handle READING_FIRMWARE_PREALLOC_BUFFER at all, here
are bits of code from: security/integrity/ima/ima_main.c:

static int read_idmap[READING_MAX_ID] = {
         [READING_FIRMWARE] = FIRMWARE_CHECK,
         [READING_MODULE] = MODULE_CHECK,
         [READING_KEXEC_IMAGE] = KEXEC_KERNEL_CHECK,
         [READING_KEXEC_INITRAMFS] = KEXEC_INITRAMFS_CHECK,
         [READING_POLICY] = POLICY_CHECK
};

int ima_post_read_file(struct file *file, void *buf, loff_t size,
	...
         if (!file && read_id == READING_FIRMWARE) {
                 if ((ima_appraise & IMA_APPRAISE_FIRMWARE) &&
                     (ima_appraise & IMA_APPRAISE_ENFORCE))
                         return -EACCES; /* INTEGRITY_UNKNOWN */
                 return 0;
         }

Which show that the IMA code is not handling
READING_FIRMWARE_PREALLOC_BUFFER as it should (I believe it
should handle it the same as READING_FIRMWARE).

Now we could fix that, but the only user of
READING_FIRMWARE_PREALLOC_BUFFER is the code which originally
introduced it:

https://patchwork.kernel.org/patch/9162011/

So I believe it might be better to instead replace it
with just READING_FIRMWARE and find another way to tell
kernel_read_file() that there is a pre-allocated buffer,
perhaps the easiest way there is that  *buf must be
NULL when the caller wants kernel_read_file() to
vmalloc the mem. This would of course require auditing
all callers that the buf which the pass in is initialized
to NULL.

Either way adding a third READING_FIRMWARE_FOO to the
kernel_read_file_id enum seems like a bad idea, from
the IMA pov firmware is firmware.

What this whole exercise has shown me though is that
I need to call security_kernel_post_read_file() when
loading EFI embedded firmware. I will add a call to
security_kernel_post_read_file() for v4 of the patch-set.

> Please Cc Kees in future patches.

Will do.

Regards,

Hans

  reply	other threads:[~2018-04-24 15:09 UTC|newest]

Thread overview: 36+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-04-08 17:40 [PATCH v3 0/5] efi/firmware/platform-x86: Add EFI embedded fw support Hans de Goede
2018-04-08 17:40 ` [PATCH v3 1/5] efi: Export boot-services code and data as debugfs-blobs Hans de Goede
2018-04-16  8:23   ` Ard Biesheuvel
2018-04-24 13:11     ` Hans de Goede
2018-04-23 11:55   ` Greg Kroah-Hartman
2018-04-08 17:40 ` [PATCH v3 2/5] efi: Add embedded peripheral firmware support Hans de Goede
2018-04-16  8:28   ` Ard Biesheuvel
2018-04-24 13:17     ` Hans de Goede
2018-04-17  0:17   ` Luis R. Rodriguez
2018-04-17  8:58     ` Hans de Goede
2018-04-17  9:19     ` Hans de Goede
2018-04-23 21:11   ` Luis R. Rodriguez
2018-04-24 15:09     ` Hans de Goede [this message]
2018-04-24 16:07       ` Mimi Zohar
2018-04-24 18:33         ` Hans de Goede
2018-04-24 23:42         ` Luis R. Rodriguez
2018-04-25  5:00           ` Mimi Zohar
2018-04-25 17:55             ` Luis R. Rodriguez
2018-05-04  0:21               ` Luis R. Rodriguez
2018-05-04 15:26                 ` Martijn Coenen
2018-05-04 19:44               ` Martijn Coenen
2018-05-08 15:38                 ` Luis R. Rodriguez
2018-05-08 16:10                   ` Luis R. Rodriguez
2018-06-07 16:49                     ` Bjorn Andersson
2018-06-07 18:22                       ` Luis R. Rodriguez
2018-06-01 19:23                   ` Luis R. Rodriguez
2018-06-06 20:32                     ` Do Qualcomm drivers use DMA buffers for request_firmware_into_buf()? Luis R. Rodriguez
2018-06-07 16:18                       ` Bjorn Andersson
     [not found]                         ` <CAKv+Gu8+Fq7BD4XD-YCyXzZh0mg6Z2k-0styj0cw6_uZfaqy4Q@mail.gmail.com>
     [not found]                           ` <20180607163308.GA18834@kroah.com>
2018-06-08  6:41                             ` Vlastimil Babka
2018-06-07 16:33             ` [PATCH v3 2/5] efi: Add embedded peripheral firmware support Bjorn Andersson
2018-04-08 17:40 ` [PATCH v3 3/5] platform/x86: Rename silead_dmi to touchscreen_dmi Hans de Goede
2018-04-09  8:07   ` Andy Shevchenko
2018-04-20  0:20     ` Darren Hart
2018-04-08 17:40 ` [PATCH v3 4/5] platform/x86: touchscreen_dmi: Add EFI embedded firmware info support Hans de Goede
2018-04-08 17:40 ` [PATCH v3 5/5] platform/x86: touchscreen_dmi: Add info for the Chuwi Vi8 Plus tablet Hans de Goede
2018-04-09  8:10   ` Andy Shevchenko

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