VULNERABILITY

Debian: CVE-2025-21696: linux -- security update

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Debian: CVE-2025-21696: linux -- security update

Severity
5
CVSS
(AV:L/AC:L/Au:S/C:N/I:N/A:C)
Published
02/12/2025
Created
05/16/2025
Added
05/15/2025
Modified
05/27/2025

Description

In the Linux kernel, the following vulnerability has been resolved: mm: clear uffd-wp PTE/PMD state on mremap() When mremap()ing a memory region previously registered with userfaultfd as write-protected but without UFFD_FEATURE_EVENT_REMAP, an inconsistency in flag clearing leads to a mismatch between the vma flags (which have uffd-wp cleared) and the pte/pmd flags (which do not have uffd-wp cleared). This mismatch causes a subsequent mprotect(PROT_WRITE) to trigger a warning in page_table_check_pte_flags() due to setting the pte to writable while uffd-wp is still set. Fix this by always explicitly clearing the uffd-wp pte/pmd flags on any such mremap() so that the values are consistent with the existing clearing of VM_UFFD_WP. Be careful to clear the logical flag regardless of its physical form; a PTE bit, a swap PTE bit, or a PTE marker. Cover PTE, huge PMD and hugetlb paths.

Solution(s)

  • no-fix-debian-deb-package

References

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