CVE-2021-47318

/// Technical description

In the Linux kernel, the following vulnerability has been resolved:

arch_topology: Avoid use-after-free for scale_freq_data

Currently topology_scale_freq_tick() (which gets called from

scheduler_tick()) may end up using a pointer to "struct

scale_freq_data", which was previously cleared by

topology_clear_scale_freq_source(), as there is no protection in place

here. The users of topology_clear_scale_freq_source() though needs a

guarantee that the previously cleared scale_freq_data isn't used

anymore, so they can free the related resources.

Since topology_scale_freq_tick() is called from scheduler tick, we don't

want to add locking in there. Use the RCU update mechanism instead

(which is already used by the scheduler's utilization update path) to

guarantee race free updates here.

synchronize_rcu() makes sure that all RCU critical sections that started

before it is called, will finish before it returns. And so the callers

of topology_clear_scale_freq_source() don't need to worry about

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References