linux-hardening - Re: [PATCH v2 07/14] mfd: zl3073x: Add components versions register defs

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Message-ID: <003bfece-7487-4c65-b4f1-2de59207bd5d@redhat.com>
Date: Thu, 10 Apr 2025 20:44:43 +0200
From: Ivan Vecera <ivecera@...hat.com>
To: Andrew Lunn <andrew@...n.ch>
Cc: Krzysztof Kozlowski <krzk@...nel.org>, netdev@...r.kernel.org,
 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>, Michal Schmidt <mschmidt@...hat.com>,
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-hardening@...r.kernel.org
Subject: Re: [PATCH v2 07/14] mfd: zl3073x: Add components versions register
 defs



On 10. 04. 25 7:41 odp., Andrew Lunn wrote:
>>>> +	/* Take device lock */
>>>
>>> What is a device lock? Why do you need to comment standard guards/mutexes?
>>
>> Just to inform code reader, this is a section that accesses device registers
>> that are protected by this zl3073x device lock.
> 
> I didn't see a reply to my question about the big picture. Why is the
> regmap lock not sufficient. Why do you need a device lock.
> 
>>
>>>> +	scoped_guard(zl3073x, zldev) {
>>>> +		rc = zl3073x_read_id(zldev, &id);
>>>> +		if (rc)
>>>> +			return rc;
>>>> +		rc = zl3073x_read_revision(zldev, &revision);
>>>> +		if (rc)
>>>> +			return rc;
>>>> +		rc = zl3073x_read_fw_ver(zldev, &fw_ver);
>>>> +		if (rc)
>>>> +			return rc;
>>>> +		rc = zl3073x_read_custom_config_ver(zldev, &cfg_ver);
>>>> +		if (rc)
>>>> +			return rc;
>>>> +	}
>>>
>>> Nothing improved here. Andrew comments are still valid and do not send
>>> v3 before the discussion is resolved.
>>
>> I'm accessing device registers here and they are protected by the device
>> lock. I have to take the lock, register access functions expect this by
>> lockdep_assert.
> 
> Because lockdep asserts is not a useful answer. Locks are there to
> protect you from something. What are you protecting yourself from? If
> you cannot answer that question, your locking scheme is built on sand
> and very probably broken.
> 
>      Andrew

Hi Andrew,
I have described the locking requirements under different message [v1 
05/28]. Could you please take a look?

Thanks,
Ivan