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

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Message-ID: <20250924-fancy-bull-of-opposition-0be83a@sudeepholla>
Date: Wed, 24 Sep 2025 09:41:05 +0100
From: Sudeep Holla <sudeep.holla@....com>
To: "Kumar, Kaushlendra" <kaushlendra.kumar@...el.com>
Cc: "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
	Sudeep Holla <sudeep.holla@....com>,
	"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 06:03:08PM +0000, Kumar, Kaushlendra wrote:
> 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 are welcome.

> 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.
> 

Please take a look at these
https://lkml.org/lkml/2020/6/28/157
https://lkml.org/lkml/2024/6/25/1026
https://lkml.org/lkml/2024/1/30/1116
https://lkml.org/lkml/2025/9/2/812

> 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.
> 

Thanks.

> If possible you can ignore the later version of patch.
> 

Hmm, I see you have managed to send v4 before seeing my response on v1 and v3
and hence didn't add my review tag 🙁.

-- 
Regards,
Sudeep