linux-kernel - Re: [PATCH v3 2/5] efi: Add embedded peripheral firmware support

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Date:   Tue, 24 Apr 2018 20:33:54 +0200
From:   Hans de Goede <hdegoede@...hat.com>
To:     Mimi Zohar <zohar@...ux.vnet.ibm.com>,
        "Luis R. Rodriguez" <mcgrof@...nel.org>,
        Kees Cook <keescook@...omium.org>
Cc:     Darren Hart <dvhart@...radead.org>,
        Andy Shevchenko <andy@...radead.org>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H . Peter Anvin" <hpa@...or.com>,
        platform-driver-x86@...r.kernel.org, linux-kernel@...r.kernel.org,
        Peter Jones <pjones@...hat.com>,
        Dave Olsthoorn <dave@...aar.me>,
        Will Deacon <will.deacon@....com>,
        Andy Lutomirski <luto@...nel.org>,
        Matt Fleming <matt@...eblueprint.co.uk>,
        David Howells <dhowells@...hat.com>,
        Josh Triplett <josh@...htriplett.org>,
        dmitry.torokhov@...il.com, mfuzzey@...keon.com,
        Kalle Valo <kvalo@...eaurora.org>,
        Arend Van Spriel <arend.vanspriel@...adcom.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        nbroeking@...com, bjorn.andersson@...aro.org,
        Torsten Duwe <duwe@...e.de>, x86@...nel.org,
        linux-efi@...r.kernel.org
Subject: Re: [PATCH v3 2/5] efi: Add embedded peripheral firmware support

Hi,

On 24-04-18 18:07, Mimi Zohar wrote:
> On Tue, 2018-04-24 at 17:09 +0200, Hans de Goede wrote:
>> 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,
> 
> Right, it doesn't yet address READING_FIRMWARE_PREALLOC_BUFFER, but
> should.
> 
> Depending on whether the device requesting the firmware has access to
> the DMA memory, before the signature verification, will determine how
> IMA-appraisal addresses READING_FIRMWARE_PREALLOC_BUFFER.

Ah I see. So this probably means that the IMA integration for
my EFI embedded firmware code should also pass READING_FIRMWARE or
READING_FIRMWARE_PREALLOC_BUFFER depending on if a pre-allocated
buffer is used.

Hmm, the security_kernel_post_read_file() call in
drivers/base/firmware_loader/fallback.c

Unconditionally passes READING_FIRMWARE, it should probably check
fw_priv->is_paged_buf and base the id to pass on that.

And yes it is possible AFAICT for the firmware_request_into_buf()
method to fallback to the userspace helper, this can happen if the
fw_fallback_config.force_sysfs_fallback flag is set.

Regards,

Hans