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bdu:2025-11992

BELL-CVE-2025-21984

Affected: Alpaquita:25: linux-lts, Alpaquita:stream: linux-lts

certfr-2025-avi-0559 — De multiples vulnérabilités ont été découvertes dans le noyau Linux d'Ubuntu. Certaines d'entre elles permettent à un a…

certfr-2025-avi-0559

EUVD-2026-346734

fkie_cve-2025-21984

In the Linux kernel, the following vulnerability has been resolved:

mm: fix kernel BUG when userfaultfd_move encounters swapcache

userfaultfd_move() checks whether the PTE entry is present or a swap entry.

- If the PTE entry is present, move_present_pte() handles folio migration by setting:

src_folio->index = linear_page_index(dst_vma, dst_addr);

- If the PTE entry is a swap entry, move_swap_pte() simply copies the PTE to the new dst_addr.

This approach is incorrect because, even if the PTE is a swap entry, it can still reference a folio that remains in the swap cache.

This creates a race window between steps 2 and 4. 1. add_to_swap: The folio is added to the swapcache. 2. try_to_unmap: PTEs are converted to swap entries. 3. pageout: The folio is written back. 4. Swapcache is cleared. If userfaultfd_move() occurs in the window between steps 2 and 4, after the swap PTE has been moved to the destination, accessing the destination triggers do_swap_page(), which may locate the folio in the swapcache. However, since the folio's index has not been updated to match the destination VMA, do_swap_page() will detect a mismatch.

This can result in two critical issues depending on the system configuration.

If KSM is disabled, both small and large folios can trigger a BUG during the add_rmap operation due to:

page_pgoff(folio, page) != linear_page_index(vma, address)

[ 13.336953] page: refcount:6 mapcount:1 mapping:00000000f43db19c index:0xffffaf150 pfn:0x4667c […

GHSA-mw8g-4mvm-gj4f

In the Linux kernel, the following vulnerability has been resolved:

mm: fix kernel BUG when userfaultfd_move encounters swapcache

userfaultfd_move() checks whether the PTE entry is present or a swap entry.

- If the PTE entry is present, move_present_pte() handles folio migration by setting:

src_folio->index = linear_page_index(dst_vma, dst_addr);

- If the PTE entry is a swap entry, move_swap_pte() simply copies the PTE to the new dst_addr.

This approach is incorrect because, even if the PTE is a swap entry, it can still reference a folio that remains in the swap cache.

This can result in two critical issues depending on the system configuration.

If KSM is disabled, both small and large folios can trigger a BUG during the add_rmap operation due to:

page_pgoff(folio, page) != linear_page_index(vma, address)

[ 13.336953] page: refcount:6 mapcount:1 mapping:00000000f43db19c index:0xffffaf150 pfn:0x4667c […

UBUNTU-CVE-2025-21984

Affected: Ubuntu:16.04:LTS: linux-hwe-edge, Ubuntu:18.04:LTS: linux-aws-5.0, Ubuntu:18.04:LTS: linux-aws-5.3, Ubuntu:18.04:LTS: linux-azure, Ubuntu:18.04:LTS: linux-azure-5.3, Ubuntu:18.04:LTS: linux-azure-edge, Ubuntu:18.04:LTS: linux-gcp, Ubuntu:18.04:LTS: linux-gcp-5.3, Ubuntu:18.04:LTS: linux-gke-4.15, Ubuntu:18.04:LTS: linux-gke-5.4 and 113 more

In the Linux kernel, the following vulnerability has been resolved: mm: fix kernel BUG when userfaultfd_move encounters swapcache userfaultfd_move() checks whether the PTE entry is present or a swap entry. - If the PTE entry is present, move_present_pte() handles folio migration by setting: src_folio->index = linear_page_index(dst_vma, dst_addr); - If the PTE entry is a swap entry, move_swap_pte() simply copies the PTE to the new dst_addr. This approach is incorrect because, even if the PTE is a swap entry, it can still reference a folio that remains in the swap cache. This creates a race window between steps 2 and 4. 1. add_to_swap: The folio is added to the swapcache. 2. try_to_unmap: PTEs are converted to swap entries. 3. pageout: The folio is written back. 4. Swapcache is cleared. If userfaultfd_move() occurs in the window between steps 2 and 4, after the swap PTE has been moved to the destination, accessing the destination triggers do_swap_page(), which may locate the folio in the swapcache. However, since the folio's index has not been updated to match the destination VMA, do_swap_page() will detect a mismatch. This can result in two critical issues depending on the system configuration. If KSM is disabled, both small and large folios can trigger a BUG during the add_rmap operation due to: page_pgoff(folio, page) != linear_page_index(vma, address) [ 13.336953] page: refcount:6 mapcount:1 mapping:00000000f43db19c index:0xffffaf150 pfn:0x4667c [ 13.337520]…

WID-SEC-W-2025-0683 — Linux Kernel: Mehrere Schwachstellen

Ein Angreifer kann mehrere Schwachstellen in Linux Kernel ausnutzen, um einen Denial-of-Service auszulösen und um nicht näher spezifizierte Auswirkungen zu erzielen.