[PATCH 2/2] platform/x86/intel: power-domains: Handle failed init in tpmi_get_power_domain_mask()

[Kristen Carlson Accardi]

tpmi_init() returns early on CPU models that are not in tpmi_cpu_ids,
before tpmi_power_domain_mask is allocated. When the driver is built
in, the exported tpmi_get_power_domain_mask() remains callable after
the failed init. It returns NULL then only because it indexes the NULL
array at offset 0 for the zeroed per-CPU data. If cpuhp_setup_state()
fails, the error path frees the array but leaves the pointer set, so
the helper would return a pointer into freed memory.

Nothing in the tree calls tpmi_get_power_domain_mask() today, so this
is hardening rather than a fix for a reachable bug. Return NULL when
the array was not allocated, and clear the pointer wherever it is
freed, as the previous patch does for domain_die_map.

Assisted-by: LLM
Signed-off-by: Kristen Carlson Accardi <kristen.c.accardi@xxxxxxxxx>
---
 drivers/platform/x86/intel/tpmi_power_domains.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/platform/x86/intel/tpmi_power_domains.c b/drivers/platform/x86/intel/tpmi_power_domains.c
index ea51fc56297d..d89b9894c42a 100644
--- a/drivers/platform/x86/intel/tpmi_power_domains.c
+++ b/drivers/platform/x86/intel/tpmi_power_domains.c
@@ -139,6 +139,13 @@ cpumask_t *tpmi_get_power_domain_mask(int cpu_no)
 	cpumask_t *mask;
 	int index;
 
+	/*
+	 * When built in, this stays callable after tpmi_init() failed
+	 * before allocating the array.
+	 */
+	if (!tpmi_power_domain_mask)
+		return NULL;
+
 	if (cpu_no >= num_possible_cpus())
 		return NULL;
 
@@ -256,6 +263,7 @@ static int __init tpmi_init(void)
 
 free_domain_mask:
 	kfree(tpmi_power_domain_mask);
+	tpmi_power_domain_mask = NULL;
 
 	return ret;
 }
@@ -265,6 +273,7 @@ static void __exit tpmi_exit(void)
 {
 	cpuhp_remove_state(tpmi_hp_state);
 	kfree(tpmi_power_domain_mask);
+	tpmi_power_domain_mask = NULL;
 	kfree(domain_die_map);
 	domain_die_map = NULL;
 }
-- 
2.55.0