CVE-2026-93218
Received Received - Intake

Race Condition in Linux Kernel Huge Memory Handling

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: mm/huge_memory: skip device-private PMDs in madvise_free_huge_pmd madvise_free_pte_range() checks pmd_trans_huge(*pmd) unlocked, then madvise_free_huge_pmd() takes pmd_trans_huge_lock(). pmd_is_huge() returns true for a device-private PMD, so orig_pmd can be device-private and enter the !pmd_present() branch. Skip device-private PMDs in that non-present branch and continue to out before calling pmd_folio(). Downgrade the check to VM_WARN_ON_ONCE() so an unexpected PMD softleaf logs a warning rather than panicking. Drop the thp_migration_supported() guard: it expands to IS_ENABLED(CONFIG_ARCH_SUPPORTS_PMD_SOFTLEAF), and both pmd_is_migration_entry() and pmd_is_device_private_entry() already return false when that config is not selected, so the guard suppresses only the case where the warning would already be silent. Potential trigger: an HMM-based GPU driver races with madvise(MADV_FREE): migrate_vma_pages() flips the PMD to a device-private entry between the caller's pmd_trans_huge() check and the callee's pmd_trans_huge_lock().

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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-2026-93218
EUVD
EUVD-2026-85947

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 race condition in the madvise_free_huge_pmd function. It occurs when an HMM-based GPU driver interacts with madvise(MADV_FREE), causing a PMD to flip to a device-private entry between checks. This can lead to incorrect handling of huge pages and potential system instability.

Detection Guidance

This vulnerability is specific to the Linux kernel and requires kernel-level detection. Check your kernel version with 'uname -r' and compare it against patched versions. Monitor kernel logs for warnings related to PMD handling or madvise operations. Look for GPU driver crashes or memory management errors.

Impact Analysis

The vulnerability may cause system crashes or unexpected behavior due to improper handling of huge pages. Users relying on GPU drivers or memory management features could experience performance issues or application failures.

Mitigation Strategies

Update your Linux kernel to the latest stable version that includes the fix. If using HMM-based GPU drivers, check for driver updates from your GPU vendor. Monitor system logs for related errors and apply kernel patches as they become available.

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