fs/resctrl: Fix UAF from worker threads when domains are removed

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Summary

CVECVE-2026-93099
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-09-17 17:18:04 UTC
Updated2026-09-17 17:18:04 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: fs/resctrl: Fix UAF from worker threads when domains are removed The mbm_handle_overflow() and cqm_handle_limbo() workers read event counters and may sleep while doing so. They are scheduled via delayed_work embedded in struct rdt_l3_mon_domain. Architecture allocates and frees these domains from CPU hotplug callbacks under cpus_write_lock(), and the workers acquire cpus_read_lock() to keep the domain alive across their access. A use-after-free can occur when a worker is blocked waiting for cpus_read_lock() while the hotplug core holds cpus_write_lock(): the architecture frees the rdt_l3_mon_domain that contains the worker's work_struct. When the worker unblocks, the container_of() it performs on the embedded work pointer dereferences freed memory. Drop cpus_read_lock() from the workers and instead drain pending and in-flight work synchronously before the architecture can free the domain. Since architecture offlines the domain under cpus_write_lock() after it has been unlinked from the RCU list and a grace period has elapsed, no new work can be scheduled. The cancel only needs to wait out existing work. Drop rdtgroup_mutex during CPU offline around cancel_delayed_work_sync() so that a worker waiting on the mutex can complete before re-pinning the work on a different CPU. When offlining a CPU the architecture may iterate over resources in any order. For example, the MBA control domain may be offlined before or after a corresponding L3 monitor domain. Ensure that resctrl fs cancels the workers no matter what order the architecture offlines the domains.

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 24247aeeabe99eab13b798ccccc2dec066dd6f07 b86dbfe4583bf134932a6cc45bf25b12c10a0b2f git Not specified
CNA Linux Linux affected 24247aeeabe99eab13b798ccccc2dec066dd6f07 2566b5cd6a275c124e8f154fef6e815f92ec8d5c git Not specified
CNA Linux Linux affected 4.14 Not specified
CNA Linux Linux unaffected 4.14 semver Not specified
CNA Linux Linux unaffected 7.2.6 7.2.* semver Not specified
CNA Linux Linux unaffected 7.3-rc1 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/b86dbfe4583bf134932a6cc45bf25b12c10a0b2f 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/2566b5cd6a275c124e8f154fef6e815f92ec8d5c 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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