diff mbox series

[v7,2/4] arm64: amu: Delay allocating cpumask for AMU FIE support

Message ID 20240913132944.1880703-3-beata.michalska@arm.com
State New
Headers show
Series Add support for AArch64 AMUv1-based average freq | expand

Commit Message

Beata Michalska Sept. 13, 2024, 1:29 p.m. UTC
For the time being, the amu_fie_cpus cpumask is being exclusively used
by the AMU-related internals of FIE support and is guaranteed to be
valid on every access currently made. Still the mask is not being
invalidated on one of the error handling code paths, which leaves
a soft spot with theoretical risk of UAF for CPUMASK_OFFSTACK cases.
To make things sound, delay allocating said cpumask
(for CPUMASK_OFFSTACK) avoiding otherwise nasty sanitising case failing
to register the cpufreq policy notifications.

Signed-off-by: Beata Michalska <beata.michalska@arm.com>
---
 arch/arm64/kernel/topology.c | 22 ++++++++++------------
 1 file changed, 10 insertions(+), 12 deletions(-)
diff mbox series

Patch

diff --git a/arch/arm64/kernel/topology.c b/arch/arm64/kernel/topology.c
index 1a2c72f3e7f8..cb180684d10d 100644
--- a/arch/arm64/kernel/topology.c
+++ b/arch/arm64/kernel/topology.c
@@ -194,12 +194,19 @@  static void amu_fie_setup(const struct cpumask *cpus)
 	int cpu;
 
 	/* We are already set since the last insmod of cpufreq driver */
-	if (unlikely(cpumask_subset(cpus, amu_fie_cpus)))
+	if (cpumask_available(amu_fie_cpus) &&
+	    unlikely(cpumask_subset(cpus, amu_fie_cpus)))
 		return;
 
-	for_each_cpu(cpu, cpus) {
+	for_each_cpu(cpu, cpus)
 		if (!freq_counters_valid(cpu))
 			return;
+
+	if (!cpumask_available(amu_fie_cpus) &&
+	    !zalloc_cpumask_var(&amu_fie_cpus, GFP_KERNEL)) {
+		WARN_ONCE(1, "Failed to allocate FIE cpumask for CPUs[%*pbl]\n",
+			  cpumask_pr_args(cpus));
+		return;
 	}
 
 	cpumask_or(amu_fie_cpus, amu_fie_cpus, cpus);
@@ -237,17 +244,8 @@  static struct notifier_block init_amu_fie_notifier = {
 
 static int __init init_amu_fie(void)
 {
-	int ret;
-
-	if (!zalloc_cpumask_var(&amu_fie_cpus, GFP_KERNEL))
-		return -ENOMEM;
-
-	ret = cpufreq_register_notifier(&init_amu_fie_notifier,
+	return cpufreq_register_notifier(&init_amu_fie_notifier,
 					CPUFREQ_POLICY_NOTIFIER);
-	if (ret)
-		free_cpumask_var(amu_fie_cpus);
-
-	return ret;
 }
 core_initcall(init_amu_fie);