linux-kernel - [PATCH v2] arch_topology: Fix incorrect error check in topology_parse_cpu

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Message-Id: <20250923084610.3995594-1-kaushlendra.kumar@intel.com>
Date: Tue, 23 Sep 2025 14:16:10 +0530
From: Kaushlendra Kumar <kaushlendra.kumar@...el.com>
To: sudeep.holla@....com,
	gregkh@...uxfoundation.org,
	dakr@...nel.org,
	rafael@...nel.org
Cc: linux-kernel@...r.kernel.org,
	Kaushlendra Kumar <kaushlendra.kumar@...el.com>
Subject: [PATCH v2] arch_topology: Fix incorrect error check in topology_parse_cpu_capacity()

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")

Signed-off-by: Kaushlendra Kumar <kaushlendra.kumar@...el.com>
---
Changes in v2:
- Refined description based on documented macro properties (suggested by Markus Elfring)
- Added proper Fixes
---
 drivers/base/arch_topology.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/base/arch_topology.c b/drivers/base/arch_topology.c
index 1037169abb45..e1eff05bea4a 100644
--- a/drivers/base/arch_topology.c
+++ b/drivers/base/arch_topology.c
@@ -292,7 +292,7 @@ bool __init topology_parse_cpu_capacity(struct device_node *cpu_node, int cpu)
 		 * frequency (by keeping the initial capacity_freq_ref value).
 		 */
 		cpu_clk = of_clk_get(cpu_node, 0);
-		if (!PTR_ERR_OR_ZERO(cpu_clk)) {
+		if (!IS_ERR_OR_NULL(cpu_clk)) {
 			per_cpu(capacity_freq_ref, cpu) =
 				clk_get_rate(cpu_clk) / HZ_PER_KHZ;
 			clk_put(cpu_clk);
-- 
2.34.1