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

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Message-ID: <aNJ1aY0AuATEKjDN@stanley.mountain>
Date: Tue, 23 Sep 2025 13:24:41 +0300
From: Dan Carpenter <dan.carpenter@...aro.org>
To: Sudeep Holla <sudeep.holla@....com>
Cc: Kaushlendra Kumar <kaushlendra.kumar@...el.com>,
	gregkh@...uxfoundation.org, dakr@...nel.org, rafael@...nel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] arch_topology: Fix incorrect error check in
 topology_parse_cpu_capacity()

On Tue, Sep 23, 2025 at 09:40:28AM +0100, Sudeep Holla wrote:
> On Tue, Sep 23, 2025 at 12:55:20PM +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().
> > 
> > PTR_ERR_OR_ZERO(cpu_clk) returns:
> > - 0 if cpu_clk is a valid pointer or NULL
> > - error code if cpu_clk is an error pointer
> > 
> > Therefore !PTR_ERR_OR_ZERO(cpu_clk) is true for both valid pointers and
> > NULL, causing the code to call clk_get_rate(NULL) when of_clk_get()
> > returns NULL. Replace with IS_ERR_OR_NULL() which correctly identifies
> > only valid pointers, ensuring clk_get_rate() is called only with valid
> > clock objects.
> >
> 
> Nice catch, wonder how it survived so long unnoticed.

I don't think of_clk_get() can actually return NULL...  It's still worth
fixing but I don't think it affects real life.

regards,
dan carpenter