linux-kernel - RE: [PATCH v3] arch_topology: Fix incorrect error check in topology_parse_cpu

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Message-ID: <LV3PR11MB8768C62AFE6332ECDE9366EFF51DA@LV3PR11MB8768.namprd11.prod.outlook.com>
Date: Tue, 23 Sep 2025 18:03:08 +0000
From: "Kumar, Kaushlendra" <kaushlendra.kumar@...el.com>
To: Sudeep Holla <sudeep.holla@....com>
CC: "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
	"dakr@...nel.org" <dakr@...nel.org>, "rafael@...nel.org" <rafael@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"stable@...r.kernel.org" <stable@...r.kernel.org>
Subject: RE: [PATCH v3] arch_topology: Fix incorrect error check in
 topology_parse_cpu_capacity()

On Tue, Sep 23, 2025 at 3:30 PM, Sudeep Holla <sudeep.holla@....com> wrote:
> On Tue, Sep 23, 2025 at 03:15:14PM +0530, Kaushlendra Kumar wrote:
> > Fix incorrect use of PTR_ERR_OR_ZERO() in 
> > topology_parse_cpu_capacity() which causes the code to proceed with 
> > NULL clock pointers. The current logic uses !PTR_ERR_OR_ZERO(cpu_clk) 
> > which evaluates to true for both valid pointers and NULL, leading to 
> > potential NULL pointer dereference in clk_get_rate().
> > 
> > Per include/linux/err.h documentation, PTR_ERR_OR_ZERO(ptr) returns:
> > "The error code within @ptr if it is an error pointer; 0 otherwise."
> > 
> > This means PTR_ERR_OR_ZERO() returns 0 for both valid pointers AND 
> > NULL pointers. Therefore !PTR_ERR_OR_ZERO(cpu_clk) evaluates to true 
> > (proceed) when cpu_clk is either valid or NULL, causing 
> > clk_get_rate(NULL) to be called when of_clk_get() returns NULL.
> > 
> > Replace with !IS_ERR_OR_NULL(cpu_clk) which only proceeds for valid 
> > pointers, preventing potential NULL pointer dereference in clk_get_rate().
> > 
> > Fixes: b8fe128dad8f ("arch_topology: Adjust initial CPU capacities 
> > with current freq")
> > Cc: stable@...r.kernel.org
> > 
> 
> I wonder if you missed my response on v1[1] before you sent v2/v3 so quickly.
> The reviewed by tag still stands, just for sake of tools:
> 
> Reviewed-by: Sudeep Holla <sudeep.holla@....com>
> 
> --
> Regards,
> Sudeep
> 
> [1] https://lore.kernel.org/all/20250923-spectral-rich-shellfish-3ab26c@sudeepholla/

Hi Sudeep,

Thank you for the clarification and for providing the Reviewed-by tag!

You're absolutely right - I apologize for missing your v1 response before 
sending v2/v3. I was focused on addressing the feedback from other reviewers 
(particularly Markus Elfring's suggestions about commit message improvements 
and documentation compliance) and didn't properly check for your response first.

I really appreciate you maintaining the Reviewed-by tag through the versions, 
and I'll make sure to check all responses more carefully before sending 
subsequent versions in the future.

If possible you can ignore the later version of patch.

Thank you for the review and for pointing out this process oversight.

Best regards,
Kaushlendra