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National Vulnerability Database

National Vulnerability Database

NVD

National Vulnerability Database
  1. Vulnerabilities

CVE-2026-23100 Detail

Description

In the Linux kernel, the following vulnerability has been resolved: mm/hugetlb: fix hugetlb_pmd_shared() Patch series "mm/hugetlb: fixes for PMD table sharing (incl. using mmu_gather)", v3. One functional fix, one performance regression fix, and two related comment fixes. I cleaned up my prototype I recently shared [1] for the performance fix, deferring most of the cleanups I had in the prototype to a later point. While doing that I identified the other things. The goal of this patch set is to be backported to stable trees "fairly" easily. At least patch #1 and #4. Patch #1 fixes hugetlb_pmd_shared() not detecting any sharing Patch #2 + #3 are simple comment fixes that patch #4 interacts with. Patch #4 is a fix for the reported performance regression due to excessive IPI broadcasts during fork()+exit(). The last patch is all about TLB flushes, IPIs and mmu_gather. Read: complicated There are plenty of cleanups in the future to be had + one reasonable optimization on x86. But that's all out of scope for this series. Runtime tested, with a focus on fixing the performance regression using the original reproducer [2] on x86. This patch (of 4): We switched from (wrongly) using the page count to an independent shared count. Now, shared page tables have a refcount of 1 (excluding speculative references) and instead use ptdesc->pt_share_count to identify sharing. We didn't convert hugetlb_pmd_shared(), so right now, we would never detect a shared PMD table as such, because sharing/unsharing no longer touches the refcount of a PMD table. Page migration, like mbind() or migrate_pages() would allow for migrating folios mapped into such shared PMD tables, even though the folios are not exclusive. In smaps we would account them as "private" although they are "shared", and we would be wrongly setting the PM_MMAP_EXCLUSIVE in the pagemap interface. Fix it by properly using ptdesc_pmd_is_shared() in hugetlb_pmd_shared().


Metrics

 
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CVSS 4.0 Severity and Vector Strings:

NIST CVSS score
NIST: NVD
N/A
NVD assessment not yet provided.

References to Advisories, Solutions, and Tools

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URL Source(s) Tag(s)
https://cert-portal.siemens.com/productcert/html/ssa-019113.html siemens-SADP
https://cert-portal.siemens.com/productcert/html/ssa-082556.html siemens-SADP
https://git.kernel.org/stable/c/3a18b452dd5f7f1652c2e92f8ae769aa17a66c9e kernel.org Patch 
https://git.kernel.org/stable/c/51dcf459845fd28f5a0d83d408a379b274ec5cc5 kernel.org Patch 
https://git.kernel.org/stable/c/5b2aec77f92265a9028c5f632bdd9af5b57ec3a3 kernel.org
https://git.kernel.org/stable/c/69c4e241ff13545d410a8b2a688c932182a858bf kernel.org Patch 
https://git.kernel.org/stable/c/8ae48255bcb17b32436be97553dca848730d365f kernel.org
https://git.kernel.org/stable/c/bf3c2affe245cf831866ddc8f736ae6a22cdc11c kernel.org
https://git.kernel.org/stable/c/ca1a47cd3f5f4c46ca188b1c9a27af87d1ab2216 kernel.org Patch 

Weakness Enumeration

CWE-ID CWE Name Source
NVD-CWE-noinfo Insufficient Information cwe source acceptance level NIST  

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Change History

7 change records found show changes

Quick Info

CVE Dictionary Entry:
CVE-2026-23100
NVD Published Date:
02/04/2026
NVD Last Modified:
07/14/2026
Source:
kernel.org