Linux Kernel up to 5.13.3 arch_topology topology_scale_freq_tick use after free

Summaryinfo

A vulnerability was found in Linux Kernel up to 5.13.3. It has been rated as problematic. This impacts the function topology_scale_freq_tick of the component arch_topology. Performing a manipulation results in use after free. This vulnerability is identified as CVE-2021-47318. There is not any exploit available. Upgrading the affected component is advised.

Detailsinfo

A vulnerability was found in Linux Kernel up to 5.13.3. It has been classified as problematic. This affects the function topology_scale_freq_tick of the component arch_topology. The manipulation with an unknown input leads to a use after free vulnerability. CWE is classifying the issue as CWE-416. Referencing memory after it has been freed can cause a program to crash, use unexpected values, or execute code. The impact remains unknown. The summary by CVE is:

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 their callback getting called anymore.

The advisory is shared at git.kernel.org. This vulnerability is uniquely identified as CVE-2021-47318 since 05/21/2024. The exploitability is told to be difficult. Technical details are known, but no exploit is available. The price for an exploit might be around USD $0-$5k at the moment (estimation calculated on 12/26/2024).

Upgrading to version 5.13.4 eliminates this vulnerability. Applying the patch ccdf7e073170/83150f5d05f0 is able to eliminate this problem. The bugfix is ready for download at git.kernel.org. The best possible mitigation is suggested to be upgrading to the latest version.

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Productinfo

Type

• Operating System

Vendor

• Linux

Name

• Kernel

Version

• 5.13.0
• 5.13.1
• 5.13.2
• 5.13.3

License

• open-source

Website

• Vendor: https://www.kernel.org/

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