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CVE-2026-31398: Linux

7.8

CVSS 3.1

Няма данни

Вероятност да бъде експлоатирана в следващите 30 дни (EPSS)

Няма потвърждение

Атакува се

Няма данни

Време до експлоатация

Атакува се локално, без особени условия, с обикновен потребителски вход и без действие от потребителя.

    Описание

    Оригинално описание

    In the Linux kernel, the following vulnerability has been resolved: mm/rmap: fix incorrect pte restoration for lazyfree folios We batch unmap anonymous lazyfree folios by folio_unmap_pte_batch. If the batch has a mix of writable and non-writable bits, we may end up setting the entire batch writable. Fix this by respecting writable bit during batching. Although on a successful unmap of a lazyfree folio, the soft-dirty bit is lost, preserve it on pte restoration by respecting the bit during batching, to make the fix consistent w.r.t both writable bit and soft-dirty bit. I was able to write the below reproducer and crash the kernel. Explanation of reproducer (set 64K mTHP to always): Fault in a 64K large folio. Split the VMA at mid-point with MADV_DONTFORK. fork() - parent points to the folio with 8 writable ptes and 8 non-writable ptes. Merge the VMAs with MADV_DOFORK so that folio_unmap_pte_batch() can determine all the 16 ptes as a batch. Do MADV_FREE on the range to mark the folio as lazyfree. Write to the memory to dirty the pte, eventually rmap will dirty the folio. Then trigger reclaim, we will hit the pte restoration path, and the kernel will crash with the trace given below. The BUG happens at: BUG_ON(atomic_inc_return(&ptc->anon_map_count) > 1 && rw); The code path is asking for anonymous page to be mapped writable into the pagetable. The BUG_ON() firing implies that such a writable page has been mapped into the pagetables of more than one process, which breaks anonymous memory/CoW semantics. [ 21.134473] kernel BUG at mm/page_table_check.c:118! [ 21.134497] Internal error: Oops - BUG: 00000000f2000800 [#1] SMP [ 21.135917] Modules linked in: [ 21.136085] CPU: 1 UID: 0 PID: 1735 Comm: dup-lazyfree Not tainted 7.0.0-rc1-00116-g018018a17770 #1028 PREEMPT [ 21.136858] Hardware name: linux,dummy-virt (DT) [ 21.137019] pstate: 21400005 (nzCv daif +PAN -UAO -TCO +DIT -SSBS BTYPE=--) [ 21.137308] pc : page_table_check_set+0x28c/0x2

    Засегнати продукти

    • Linux Linux: 354dffd29575cdf13154e8fb787322354aa9efc4 преди 99888a4f340ca8e839a0524556bd4db76d63f4e0; 354dffd29575cdf13154e8fb787322354aa9efc4 преди a0911ccdba41b0871abbf8412857bafedec3dbe1; 354dffd29575cdf13154e8fb787322354aa9efc4 преди 29f40594a28114b9a9bc87f6cf7bbee9609628f2
    • Linux Linux: 6.15; преди 6.15; 6.18.20 до 6.18.*; 6.19.10 до 6.19.*; от 7.0 нататък

    История

    • 3 април 2026 Публикувано

    Други уязвимости в Linux Linux

    Първоизточници

    CVE-2026-31398: Linux | freedomonline.bg