Linux Kernel up to 7.2.3 Huge Memory mm/huge_memory madvise_free_huge_pmd race condition

Summaryinfo

A vulnerability was found in Linux Kernel up to 7.2.3. It has been declared as very critical. Affected is the function madvise_free_huge_pmd of the file mm/huge_memory of the component Huge Memory. Executing a manipulation can lead to race condition. This vulnerability appears as CVE-2026-93218. The attack may be performed from remote. There is no available exploit. It is recommended to upgrade the affected component.

Detailsinfo

A vulnerability was found in Linux Kernel up to 7.2.3. It has been declared as very critical. This vulnerability affects the function madvise_free_huge_pmd of the file mm/huge_memory of the component Huge Memory. The manipulation with an unknown input leads to a race condition vulnerability. The CWE definition for the vulnerability is CWE-362. The product contains a code sequence that can run concurrently with other code, and the code sequence requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence that is operating concurrently. As an impact it is known to affect confidentiality, integrity, and availability. CVE summarizes:

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().

The advisory is shared for download at git.kernel.org. This vulnerability was named CVE-2026-93218 since 09/17/2026. The exploitation appears to be easy. The attack can be initiated remotely. There are known technical details, but no exploit is available. The current price for an exploit might be approx. USD $0-$5k (estimation calculated on 09/24/2026).

Upgrading to version 7.2.4 or 7.3-rc1 eliminates this vulnerability. Applying the patch 5e3026bf736498115884d6c7bd0308ba29e0474c/ce579dcf730ce5ed8043a5eeea18a3e6706a97e5 is able to eliminate this problem. 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

• 7.2.0
• 7.2.1
• 7.2.2
• 7.2.3

License

• open-source

Website

• Vendor: https://www.kernel.org/

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