CVE-2026-93253
Received Received - Intake

Memory Leak in Linux Kernel Sched Isolation

Publication date: 2026-09-24

Last updated on: 2026-09-24

Assigner: kernel.org

Description
In the Linux kernel, the following vulnerability has been resolved: sched/isolation: Defer freeing of cpumask memblock memory to initcall When testing a linux-next kernel with commit 59bd1d914bb5 ("memblock: warn when freeing reserved memory before memory map is initialized"), the following warning was hit when there was a "nohz_full" kernel boot parameter. Cannot free reserved memory because of deferred initialization of the memory map WARNING: mm/memblock.c:904 at __free_reserved_area+0xde/0xf0, CPU#0: swapper/0/0 : Call Trace: <TASK> memblock_phys_free+0xcb/0x100 housekeeping_init+0x14c/0x170 start_kernel+0x207/0x450 x86_64_start_reservations+0x24/0x30 x86_64_start_kernel+0xda/0xe0 common_startup_64+0x13e/0x141 </TASK> IOW, we shouldn't free memblock allocated memory so early in the boot process when memory map isn't fully initialized in deferred_init_memmap(). Fix it by saving the housekeeping cpumask memblock memory to be freed into a llist free list in housekeeping_init() and add a new housekeeping_late_init() helper to defer the actual freeing of memblock memory to when initcall's are being processed. The cpumask memblock memory is treated as a llist_node with the size of a "long" type which is also smallest cpumask size that can be allocated. The non-atomic version of the llist APIs are used as there is no contention. This commit depends on the presence of commit 7c2eee9c1367 ("memblock: don't touch memblock arrays when memblock_free() is called late") to prevent a KASAN UAF bug report [1]. [1] https://lore.kernel.org/lkml/20260505051821.1107133-1-longman@redhat.com/

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Meta Information

Published
2026-09-24
Last Modified
2026-09-24
Generated
2026-09-25
AI Q&A
2026-09-24
EPSS Evaluated
N/A
NVD
CVE-2026-93253
EUVD
EUVD-2026-86125

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
linux linux_kernel *

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Exploitability

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CWE ID Description
CWE-UNKNOWN

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Executive Summary

This vulnerability in the Linux kernel involves a deferred freeing issue of cpumask memblock memory during early boot. When the 'nohz_full' kernel parameter is used, the system attempts to free reserved memory before the memory map is fully initialized, triggering a warning. The fix defers this freeing to a later initcall phase using a llist free list to avoid early boot conflicts.

Detection Guidance

This vulnerability is specific to the Linux kernel and manifests during boot with a warning related to freeing reserved memory. Detection involves checking kernel boot logs for the warning message about deferred initialization of the memory map or issues with nohz_full parameter.

Impact Analysis

This vulnerability may cause system boot failures or warnings when the 'nohz_full' parameter is used. It could lead to instability or crashes during startup if the memory map is not properly initialized before freeing operations. Users relying on this kernel parameter may experience boot issues.

Compliance Impact

This vulnerability does not directly affect compliance with standards like GDPR or HIPAA as it is a low-level Linux kernel memory management issue. It may indirectly impact compliance if the kernel crash or instability causes data processing disruptions, but no direct regulatory impact is described in the provided context.

Mitigation Strategies

Apply the kernel patch that defers freeing of cpumask memblock memory to initcall. Ensure the dependency commit 7c2eee9c1367 is also applied to prevent KASAN UAF bugs. Update to a fixed kernel version if available.

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