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CVE-2021-47209
HIGH · CVSS 7.8
EPSS exploitation probability: 0%
Published 2024-04-10T19:15:48.447 · Last modified 2026-08-04T10:16:52.720

Summary

In the Linux kernel, the following vulnerability has been resolved: sched/fair: Prevent dead task groups from regaining cfs_rq's Kevin is reporting crashes which point to a use-after-free of a cfs_rq in update_blocked_averages(). Initial debugging revealed that we've live cfs_rq's (on_list=1) in an about to be kfree()'d task group in free_fair_sched_group(). However, it was unclear how that can happen. His kernel config happened to lead to a layout of struct sched_entity that put the 'my_q' member directly into the middle of the object which makes it incidentally overlap with SLUB's freelist pointer. That, in combination with SLAB_FREELIST_HARDENED's freelist pointer mangling, leads to a reliable access violation in form of a #GP which made the UAF fail fast. Michal seems to have run i

Affected products

linux — linux_kernel

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References

This product uses data from the NVD API but is not endorsed or certified by the NVD. Informational only; not professional security advice.