cpufreq: zero-initialize policy cpumask before sysfs publication
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.
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Workaround
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Fri, 25 Sep 2026 14:45:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Weaknesses | CWE-457 |
Fri, 25 Sep 2026 10:30:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Description | In the Linux kernel, the following vulnerability has been resolved: cpufreq: zero-initialize policy cpumask before sysfs publication 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. | |
| Title | cpufreq: zero-initialize policy cpumask before sysfs publication | |
| First Time appeared |
Linux
Linux linux Kernel |
|
| CPEs | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* | |
| Vendors & Products |
Linux
Linux linux Kernel |
|
| References |
|
Projects
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MITRE
Status: PUBLISHED
Assigner: Linux
Published:
Updated: 2026-09-25T10:22:31.046Z
Reserved: 2026-09-25T10:18:58.200Z
Link: CVE-2026-97905
Vulnrichment
No data.
NVD
Status : Received
Published: 2026-09-25T11:17:17.403
Modified: 2026-09-25T11:17:17.403
Link: CVE-2026-97905
Redhat
No data.
OpenCVE Enrichment
Updated: 2026-09-25T14:30:14Z