Bugzilla – Bug 1225718
VUL-0: CVE-2024-36881: kernel: mm/userfaultfd: reset ptes when close() for wr-protected ones
Last modified: 2024-06-07 17:24:06 UTC
In the Linux kernel, the following vulnerability has been resolved: mm/userfaultfd: reset ptes when close() for wr-protected ones Userfaultfd unregister includes a step to remove wr-protect bits from all the relevant pgtable entries, but that only covered an explicit UFFDIO_UNREGISTER ioctl, not a close() on the userfaultfd itself. Cover that too. This fixes a WARN trace. The only user visible side effect is the user can observe leftover wr-protect bits even if the user close()ed on an userfaultfd when releasing the last reference of it. However hopefully that should be harmless, and nothing bad should happen even if so. This change is now more important after the recent page-table-check patch we merged in mm-unstable (446dd9ad37d0 ("mm/page_table_check: support userfault wr-protect entries")), as we'll do sanity check on uffd-wp bits without vma context. So it's better if we can 100% guarantee no uffd-wp bit leftovers, to make sure each report will be valid. References: http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2024-36881 https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2024/CVE-2024-36881.mbox https://git.kernel.org/stable/c/377f3a9a3d032a52325a5b110379a25dd1ab1931 https://git.kernel.org/stable/c/8d8b68a5b0c9fb23d37df06bb273ead38fd5a29d https://git.kernel.org/stable/c/c88033efe9a391e72ba6b5df4b01d6e628f4e734 https://www.cve.org/CVERecord?id=CVE-2024-36881