Race Condition Affecting kernel-rt package, versions *
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Test your applications- Snyk IDSNYK-CENTOS8-KERNELRT-16155808
- published23 Apr 2026
- disclosed22 Apr 2026
Introduced: 22 Apr 2026
NewCVE-2026-31466 (opens in a new tab)How to fix?
There is no fixed version for Centos:8 kernel-rt.
NVD Description
Note: Versions mentioned in the description apply only to the upstream kernel-rt package and not the kernel-rt package as distributed by Centos.
See How to fix? for Centos:8 relevant fixed versions and status.
In the Linux kernel, the following vulnerability has been resolved:
mm/huge_memory: fix folio isn't locked in softleaf_to_folio()
On arm64 server, we found folio that get from migration entry isn't locked in softleaf_to_folio(). This issue triggers when mTHP splitting and zap_nonpresent_ptes() races, and the root cause is lack of memory barrier in softleaf_to_folio(). The race is as follows:
CPU0 CPU1
deferred_split_scan() zap_nonpresent_ptes() lock folio split_folio() unmap_folio() change ptes to migration entries __split_folio_to_order() softleaf_to_folio() set flags(including PG_locked) for tail pages folio = pfn_folio(softleaf_to_pfn(entry)) smp_wmb() VM_WARN_ON_ONCE(!folio_test_locked(folio)) prep_compound_page() for tail pages
In __split_folio_to_order(), smp_wmb() guarantees page flags of tail pages are visible before the tail page becomes non-compound. smp_wmb() should be paired with smp_rmb() in softleaf_to_folio(), which is missed. As a result, if zap_nonpresent_ptes() accesses migration entry that stores tail pfn, softleaf_to_folio() may see the updated compound_head of tail page before page->flags.
This issue will trigger VM_WARN_ON_ONCE() in pfn_swap_entry_folio() because of the race between folio split and zap_nonpresent_ptes() leading to a folio incorrectly undergoing modification without a folio lock being held.
This is a BUG_ON() before commit 93976a20345b ("mm: eliminate further swapops predicates"), which in merged in v6.19-rc1.
To fix it, add missing smp_rmb() if the softleaf entry is migration entry in softleaf_to_folio() and softleaf_to_page().
[tujinjiang@huawei.com: update function name and comments]
References
- https://access.redhat.com/security/cve/CVE-2026-31466
- https://git.kernel.org/stable/c/426ee10711586617da869c8bb798214965337617
- https://git.kernel.org/stable/c/4c5e7f0fcd592801c9cc18f29f80fbee84eb8669
- https://git.kernel.org/stable/c/722cfaf6b31d31123439e67b5deac6b1261a3dea
- https://git.kernel.org/stable/c/7ad1997b9bc8032603df8f091761114479285769
- https://git.kernel.org/stable/c/7ddcf4a245c1c5a91fdd9698757e3d95179ffe41
- https://git.kernel.org/stable/c/8bfb8414e9f2ce6f5f2f0e3d0da52f2d132128e7
- https://git.kernel.org/stable/c/b8c49ad888892ad7b77062b9c102b799a3e9b4f8
- https://git.kernel.org/stable/c/f1acf5887c2bbaf998dc3fe32c72b7a8b84a3ddd