Flipping firmware write-protection bits from within the kernel (was Re: [PATCH RFC platform-next 8/8] Documentation/ABI: Add new line card attributes for mlxreg-io sysfs interfaces)

Thu Mar 4 10:48:10 UTC 2021

Hi Kees, et al.,

Kees, you were the first person who came to mind to ask about this, feel free to
point me to someone else.

While reviewing a patch-set for hw-enablement of some upcoming Melanox platforms,
the addition of some sysfs files which flip write-protect bits for various firmwares
found on the platform on/off stood out to me.

As I mention in me reply to the below patch adding the docs for this at a minimum
this must (IMHO) tie into the new lockdown framework and disallow enabling
fw-updates this way depending on the lockdown mode.

Are there any other security checks which the code should/could do here ?

Maybe tie into the audit code somehow ?

Regards,

Hans

On 3/4/21 11:39 AM, Hans de Goede wrote:
> Hi,
> 
> On 2/3/21 6:36 PM, Vadim Pasternak wrote:
>> Add documentation for the new attributes for line cards:
>> - CPLDs versioning.
>> - Write protection control for 'nvram' devices.
>> - Line card reset reasons.
>> - Enabling burning of FPGA and CPLDs.
>> - Enabling burning of FPGA and gearbox SPI flashes,
>> - Enabling power of whole line card.
>> - Enabling power of QSFP ports equipped on line card.
>> - The maximum powered required for line card feeding.
>> - Line card configuration Id.
>>
>> Signed-off-by: Vadim Pasternak <vadimp at nvidia.com>
>> ---
>>  Documentation/ABI/stable/sysfs-driver-mlxreg-io | 92 +++++++++++++++++++++++++
>>  1 file changed, 92 insertions(+)
>>
>> diff --git a/Documentation/ABI/stable/sysfs-driver-mlxreg-io b/Documentation/ABI/stable/sysfs-driver-mlxreg-io
>> index 1d1a8ee59534..a22e9d6c0904 100644
>> --- a/Documentation/ABI/stable/sysfs-driver-mlxreg-io
>> +++ b/Documentation/ABI/stable/sysfs-driver-mlxreg-io
>> @@ -326,3 +326,95 @@ Description:	This file unlocks system after hardware or firmware thermal
>>  		locking.
>>  
>>  		The file is read/write.
>> +
>> +What:		/sys/devices/platform/mlxplat/i2c_mlxcpld.*/i2c-*/i2c-*/i2c-*/*-0032/mlxreg-io.*/hwmon/hwmon*/cpld1_pn
>> +What:		/sys/devices/platform/mlxplat/i2c_mlxcpld.*/i2c-*/i2c-*/i2c-*/*-0032/mlxreg-io.*/hwmon/hwmon*/cpld1_version
>> +What:		/sys/devices/platform/mlxplat/i2c_mlxcpld.*/i2c-*/i2c-*/i2c-*/*-0032/mlxreg-io.*/hwmon/hwmon*/cpld1_version_min
>> +Date:		March 2021
>> +KernelVersion:	5.12
>> +Contact:	Vadim Pasternak <vadimp at nvidia.com>
>> +Description:	These files show with which CPLD major and minor versions
>> +		and part number has been burned CPLD device on line card.
>> +
>> +		The files are read only.
>> +
>> +What:		/sys/devices/platform/mlxplat/i2c_mlxcpld.*/i2c-*/i2c-*/i2c-*/*-0032/mlxreg-io.*/hwmon/hwmon*/fpga1_pn
>> +What:		/sys/devices/platform/mlxplat/i2c_mlxcpld.*/i2c-*/i2c-*/i2c-*/*-0032/mlxreg-io.*/hwmon/hwmon*/fpga1_version
>> +What:		/sys/devices/platform/mlxplat/i2c_mlxcpld.*/i2c-*/i2c-*/i2c-*/*-0032/mlxreg-io.*/hwmon/hwmon*/fpga1_version_min
>> +Date:		March 2021
>> +KernelVersion:	5.12
>> +Contact:	Vadim Pasternak <vadimp at nvidia.com>
>> +Description:	These files show with which FPGA major and minor versions
>> +		and part number has been burned FPGA device on line card.
>> +
>> +		The files are read only.
>> +
>> +What:		/sys/devices/platform/mlxplat/i2c_mlxcpld.*/i2c-*/i2c-*/i2c-*/*-0032/mlxreg-io.*/hwmon/hwmon*/ini_wp
>> +What:		/sys/devices/platform/mlxplat/i2c_mlxcpld.*/i2c-*/i2c-*/i2c-*/*-0032/mlxreg-io.*/hwmon/hwmon*/vpd_wp
>> +Date:		March 2021
>> +KernelVersion:	5.12
>> +Contact:	Vadim Pasternak <vadimp at nvidia.com>
>> +Description:	These files allow to overwrite line card VPD and firmware blob
>> +		hardware write protection mode. When attribute is set 1 - write
>> +		protection is disabled, when 0 - enabled. By default both are
>> +		write protected.
>> +
>> +		The files are read/write.
> 
> This seems to have some serious security implications. IMHO this should be tie into the
> kernel's new(ish) lockdown system, so that if the system is in locked-down mode writing
> these will not be allowed.
> 
>> +
>> +What:		/sys/devices/platform/mlxplat/i2c_mlxcpld.*/i2c-*/i2c-*/i2c-*/*-0032/mlxreg-io.*/hwmon/hwmon*/reset_aux_pwr_or_ref
>> +What:		/sys/devices/platform/mlxplat/i2c_mlxcpld.*/i2c-*/i2c-*/i2c-*/*-0032/mlxreg-io.*/hwmon/hwmon*/reset_dc_dc_pwr_fail
>> +What:		/sys/devices/platform/mlxplat/i2c_mlxcpld.*/i2c-*/i2c-*/i2c-*/*-0032/mlxreg-io.*/hwmon/hwmon*/reset_fpga_not_done
>> +What:		/sys/devices/platform/mlxplat/i2c_mlxcpld.*/i2c-*/i2c-*/i2c-*/*-0032/mlxreg-io.*/hwmon/hwmon*/reset_from_chassis
>> +What:		/sys/devices/platform/mlxplat/i2c_mlxcpld.*/i2c-*/i2c-*/i2c-*/*-0032/mlxreg-io.*/hwmon/hwmon*/reset_line_card
>> +What:		/sys/devices/platform/mlxplat/i2c_mlxcpld.*/i2c-*/i2c-*/i2c-*/*-0032/mlxreg-io.*/hwmon/hwmon*/reset_pwr_off_from_chassis
>> +Date:		March 2021
>> +KernelVersion:	5.12
>> +Contact:	Vadim Pasternak <vadimp at nvidia.com>
>> +Description:	These files show the line reset cause, as following: power
>> +		auxiliary outage or power refresh, DC-to-DC power failure, FPGA reset
>> +		failed, line card reset failed, power off from chassis.
>> +		Value 1 in file means this is reset cause, 0 - otherwise. Only one of
>> +		the above causes could be 1 at the same time, representing only last
>> +		reset cause.
>> +
>> +		The files are read only.
>> +
>> +What:		/sys/devices/platform/mlxplat/i2c_mlxcpld.*/i2c-*/i2c-*/i2c-*/*-0032/mlxreg-io.*/hwmon/hwmon*/cpld_upgrade_en
>> +What:		/sys/devices/platform/mlxplat/i2c_mlxcpld.*/i2c-*/i2c-*/i2c-*/*-0032/mlxreg-io.*/hwmon/hwmon*/fpga_upgrade_en
>> +Date:		March 2021
>> +KernelVersion:	5.12
>> +Contact:	Vadim Pasternak <vadimp at nvidia.com>
>> +Description:	These files allow CPLD and FPGA burning. Value 1 in file means burning
>> +		is enabled, 0 - otherwise.
>> +
>> +		The files are read/write.
> 
> Same remark as above.
> 
>> +
>> +What:		/sys/devices/platform/mlxplat/i2c_mlxcpld.*/i2c-*/i2c-*/i2c-*/*-0032/mlxreg-io.*/hwmon/hwmon*/qsfp_pwr_en
>> +What:		/sys/devices/platform/mlxplat/i2c_mlxcpld.*/i2c-*/i2c-*/i2c-*/*-0032/mlxreg-io.*/hwmon/hwmon*/pwr_en
>> +Date:		March 2021
>> +KernelVersion:	5.12
>> +Contact:	Vadim Pasternak <vadimp at nvidia.com>
>> +Description:	These files allow to power on/off all QSFP ports and whole line card.
>> +		The attributes are set 1 for power on, 0 - for power off.
>> +
>> +		The files are read/write.
>> +
>> +What:		/sys/devices/platform/mlxplat/i2c_mlxcpld.*/i2c-*/i2c-*/i2c-*/*-0032/mlxreg-io.*/hwmon/hwmon*/agb_spi_burn_en
>> +What:		/sys/devices/platform/mlxplat/i2c_mlxcpld.*/i2c-*/i2c-*/i2c-*/*-0032/mlxreg-io.*/hwmon/hwmon*/fpga_spi_burn_en
>> +Date:		March 2021
>> +KernelVersion:	5.12
>> +Contact:	Vadim Pasternak <vadimp at nvidia.com>
>> +Description:	These files allow gearboxes and FPGA SPI flash burning.
>> +		The attributes are set 1 to enable burning, 0 - to disable.
>> +
>> +		The file is read/write.
> 
> Same remark as above.
> 
>> +
>> +What:		/sys/devices/platform/mlxplat/i2c_mlxcpld.*/i2c-*/i2c-*/i2c-*/*-0032/mlxreg-io.*/hwmon/hwmon*/max_power
>> +What:		/sys/devices/platform/mlxplat/i2c_mlxcpld.*/i2c-*/i2c-*/i2c-*/*-0032/mlxreg-io.*/hwmon/hwmon*/config
>> +Date:		March 2021
>> +KernelVersion:	5.12
>> +Contact:	Vadim Pasternak <vadimp at nvidia.com>
>> +Description:	These files provide the maximum powered required for line card
>> +		feeding and line card configuration Id.
>> +
>> +		The files are read only.
>>
> 
> Regards,
> 
> Hans
> 