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cpufreq: zero-initialize policy cpumask before sysfs publication

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cpufreq_policy_alloc() allocates policy->cpus with alloc_cpumask_var(),
i.e. without __GFP_ZERO, unlike the sibling related_cpus and real_cpus
masks. With CONFIG_CPUMASK_OFFSTACK=y the mask is a separate
kmalloc_node() allocation, so its bitmap holds whatever the slab allocator
left behind:

  cpufreq_online()
    cpufreq_policy_alloc()
      alloc_cpumask_var(&policy->cpus)    /* bitmap is uninitialized */
      kobject_init_and_add()              /* policy%u/ appears in sysfs */
    cpufreq_policy_online()
      cpumask_copy(policy->cpus, cpumask_of(cpu))  /* first valid value */

This leaves a window in which the sysfs attributes are already reachable
while policy->cpus is still garbage. show()/store() gate on
policy_is_inactive(), i.e. cpumask_empty(policy->cpus), so a non-zero
bitmap makes them run the attribute callbacks on a policy that is not
initialized yet.

Fix this by using zalloc_cpumask_var() for policy->cpus.

Fixes: 2fc3384dc7 ("cpufreq: Initialize policy->kobj while allocating policy")
Cc: All applicable <stable@vger.kernel.org>
Signed-off-by: Zhongqiu Han <zhongqiu.han@oss.qualcomm.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Link: https://patch.msgid.link/20260901143635.4106960-1-zhongqiu.han@oss.qualcomm.com
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
This commit is contained in:
Zhongqiu Han 2026-09-01 22:36:35 +08:00 committed by Rafael J. Wysocki
parent 3e5d1bf4bd
commit 54d37bcf2f
1 changed files with 1 additions and 1 deletions
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2
drivers/cpufreq/cpufreq.c
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@ -1249,7 +1249,7 @@ static struct cpufreq_policy *cpufreq_policy_alloc(unsigned int cpu)
if (!policy)
return NULL;
if (!alloc_cpumask_var(&policy->cpus, GFP_KERNEL))
if (!zalloc_cpumask_var(&policy->cpus, GFP_KERNEL))
goto err_free_policy;
if (!zalloc_cpumask_var(&policy->related_cpus, GFP_KERNEL))