linux-hardening - Re: [PATCH 05/28] mfd: zl3073x: Add components versions register defs

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Message-ID: <138d0e3c-ccab-48e2-b437-aec063d1d2dc@kernel.org>
Date: Thu, 10 Apr 2025 12:42:05 +0200
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Ivan Vecera <ivecera@...hat.com>, Andrew Lunn <andrew@...n.ch>
Cc: netdev@...r.kernel.org, Michal Schmidt <mschmidt@...hat.com>,
 Vadim Fedorenko <vadim.fedorenko@...ux.dev>,
 Arkadiusz Kubalewski <arkadiusz.kubalewski@...el.com>,
 Jiri Pirko <jiri@...nulli.us>, Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
 <conor+dt@...nel.org>, Prathosh Satish <Prathosh.Satish@...rochip.com>,
 Lee Jones <lee@...nel.org>, Kees Cook <kees@...nel.org>,
 Andy Shevchenko <andy@...nel.org>, Andrew Morton
 <akpm@...ux-foundation.org>, devicetree@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: Re: [PATCH 05/28] mfd: zl3073x: Add components versions register defs

On 10/04/2025 12:23, Ivan Vecera wrote:
> 
> 
> On 10. 04. 25 9:11 dop., Krzysztof Kozlowski wrote:
>> On 09/04/2025 08:44, Ivan Vecera wrote:
>>> On 07. 04. 25 11:09 odp., Andrew Lunn wrote:
>>>> On Mon, Apr 07, 2025 at 07:28:32PM +0200, Ivan Vecera wrote:
>>>>> Add register definitions for components versions and report them
>>>>> during probe.
>>>>>
>>>>> Reviewed-by: Michal Schmidt <mschmidt@...hat.com>
>>>>> Signed-off-by: Ivan Vecera <ivecera@...hat.com>
>>>>> ---
>>>>>    drivers/mfd/zl3073x-core.c | 35 +++++++++++++++++++++++++++++++++++
>>>>>    1 file changed, 35 insertions(+)
>>>>>
>>>>> diff --git a/drivers/mfd/zl3073x-core.c b/drivers/mfd/zl3073x-core.c
>>>>> index 39d4c8608a740..b3091b00cffa8 100644
>>>>> --- a/drivers/mfd/zl3073x-core.c
>>>>> +++ b/drivers/mfd/zl3073x-core.c
>>>>> @@ -1,10 +1,19 @@
>>>>>    // SPDX-License-Identifier: GPL-2.0-only
>>>>>    
>>>>> +#include <linux/bitfield.h>
>>>>>    #include <linux/module.h>
>>>>>    #include <linux/unaligned.h>
>>>>>    #include <net/devlink.h>
>>>>>    #include "zl3073x.h"
>>>>>    
>>>>> +/*
>>>>> + * Register Map Page 0, General
>>>>> + */
>>>>> +ZL3073X_REG16_DEF(id,			0x0001);
>>>>> +ZL3073X_REG16_DEF(revision,		0x0003);
>>>>> +ZL3073X_REG16_DEF(fw_ver,		0x0005);
>>>>> +ZL3073X_REG32_DEF(custom_config_ver,	0x0007);
>>>>> +
>>>>>    /*
>>>>>     * Regmap ranges
>>>>>     */
>>>>> @@ -159,10 +168,36 @@ EXPORT_SYMBOL_NS_GPL(zl3073x_dev_alloc, "ZL3073X");
>>>>>    
>>>>>    int zl3073x_dev_init(struct zl3073x_dev *zldev)
>>>>>    {
>>>>> +	u16 id, revision, fw_ver;
>>>>>    	struct devlink *devlink;
>>>>> +	u32 cfg_ver;
>>>>> +	int rc;
>>>>>    
>>>>>    	devm_mutex_init(zldev->dev, &zldev->lock);
>>>>>    
>>>>> +	scoped_guard(zl3073x, zldev) {
>>>>
>>>> Why the scoped_guard? The locking scheme you have seems very opaque.
>>>
>>> We are read the HW registers in this block and the access is protected
>>> by this device lock. Regmap locking will be disabled in v2 as this is
>>
>> Reading ID must be protected by mutex? Why and how?
> 
> Yes, the ID is read from the hardware register and HW access functions 
> are protected by zl3073x_dev->lock. The access is not protected by 

Please do not keep repeating the same. You again describe the code. We
ask why do you implement that way?

> regmap locking schema. Set of registers are indirect and are accessed by 
> mailboxes where multiple register accesses need to be done atomically.

regmap handles that, but anyway, how multiple register access to ID
registers happen? From what module? Which code does it? So they write
here something in the middle and reading would be unsynced?

> This is the reason why regmap locking is not sufficient.
Again, you explained nothing why it is not sufficient. You only keep
saying "access is protected" and therefore regmap locking is not enough.
That's not a valid argument.


Best regards,
Krzysztof