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CVE-2026-31466

mm/huge_memory: fix folio isn't locked in softleaf_to_folio()

Published
Last modified
published
Not listed in CISA KEV
Fix
Fixed in 5.10.253, 5.15.203, 6.1.168, 6.6.134, 6.12.81, and 2 more
None on Exploit-DB, Metasploit or GitHub

Summary

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]

Timeline

  1. CVE published
  2. Record last updated

Affected versions

  • Linux Linux

    From e9b61f19858a5d6c42ce2298cf138279375d0d9b · fixed in 426ee10711586617da869c8bb798214965337617; From e9b61f19858a5d6c42ce2298cf138279375d0d9b · fixed in f1acf5887c2bbaf998dc3fe32c72b7a8b84a3ddd; From e9b61f19858a5d6c42ce2298cf138279375d0d9b · fixed in 722cfaf6b31d31123439e67b5deac6b1261a3dea; From e9b61f19858a5d6c42ce2298cf138279375d0d9b · fixed in 7ddcf4a245c1c5a91fdd9698757e3d95179ffe41; From e9b61f19858a5d6c42ce2298cf138279375d0d9b · fixed in b8c49ad888892ad7b77062b9c102b799a3e9b4f8; From e9b61f19858a5d6c42ce2298cf138279375d0d9b · fixed in 7ad1997b9bc8032603df8f091761114479285769; From e9b61f19858a5d6c42ce2298cf138279375d0d9b · fixed in 8bfb8414e9f2ce6f5f2f0e3d0da52f2d132128e7; From e9b61f19858a5d6c42ce2298cf138279375d0d9b · fixed in 4c5e7f0fcd592801c9cc18f29f80fbee84eb8669

  • Linux Linux

    4.5

  • KernelLinux

    From 4.5.0 · fixed in 5.10.253; From 5.11.0 · fixed in 5.15.203; From 5.16.0 · fixed in 6.1.168; From 6.2.0 · fixed in 6.6.134; From 6.7.0 · fixed in 6.12.81; From 6.13.0 · fixed in 6.18.21; From 6.19.0 · fixed in 6.19.11

References 8

git.kernel.org