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Perez de Azpillaga" To: Andrew Morton , Mike Rapoport , David Hildenbrand , Shuah Khan , Peter Xu Cc: Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Suren Baghdasaryan , Michal Hocko , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, Muchun Song , Oscar Salvador , "Jose A. Perez de Azpillaga" Subject: [PATCH 0/2] mm/userfaultfd: recheck WP registration in the hugetlb UFFDIO_COPY retry Date: Thu, 29 Oct 2026 23:11:00 +0100 Message-ID: <20261029221129.89068-1-azpijr@gmail.com> X-Mailer: git-send-email 2.55.0 X-Archived-By: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: 5620F40002 X-Stat-Signature: yugsqrwsfqj9i3e1t9m8s33cakwbhqe1 X-Spam-Status: No, score=-10.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SPF_HELO_PASS,SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=4.0.1 X-Rspam-User: X-Rspamd-Server: rspam09 X-HE-Tag: 1793311896-491573 X-HE-Meta: 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 UsEShV2D LNyXIVFN3SwHfFKpDjp2um4XBsfZx2mxXc16e8xTfMIRsLp+7RKNMf6AHHTS7nBBpV2j0kCWyGaDQHKBhgsbBdJ60JRClehSY7aN7Xs183MYcTF7ctV7g2XUtW3fCBWAA1nBNNHo5dNR2lUf/9jS2PKIkgTiW0VH+rUgKfmUOFEZmSmYVNmD6IFeg77ZrEI80sboq0XdGvAVt6pBFcWaqzcX8A/2FCO9hGMy3vjw3byGzV9gllPH4B1COd7HwBwoUOWW+oU1DmAfizofo1fgLRQVXRGxaWAM84T0TwQGZlqS+41gUSutoUlod2WDklwx6w4zpnuX69YSeWkUNctFsjRifeKs/j/UKDd0NqJbdLtmv8Q22tP6iFLbnHFOzHiUJ+vjz6TeiFn4L/ucZIqUb+HKs5kC09g3kX/86AZKFQ7oAM4XeFAS1AHpipxX6MoHcIyl6uRNWTCUieqw= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 The urgent fixes made hugetlb_fault() tolerate uffd bits left in VMAs that are no longer registered for them, and asked for follow-ups that remove the sources [1]. This is one: a hugetlb UFFDIO_COPY_MODE_WP copy that has to fault in its source page doesn't recheck the WP registration before retrying, so re-registering the range without WP in that window leaves a uffd-wp PTE behind. Patch 1 adds the check the non-hugetlb retry already gets from mfill_get_vma(). Patch 2 adds a uffd-unit-tests case for it, which fails on hugetlb without patch 1. Question: - The non-hugetlb retry compares the whole mfill_retry_state. hugetlb copies into a freshly allocated folio, so only WP seemed to matter there. Mike, would you rather have the full comparison on both paths? The other source 6/10 of [1] mentions, UFFDIO_COPY in MODE_WP racing with UFFDIO_UNREGISTER [2], is closed by "mm/userfaultfd: write-lock the VMA before waking waiters when unregistering" [3]. Based on mm-unstable. Tested on x86_64 in QEMU. [1] https://lore.kernel.org/20261015-urgent_fixes-v1-0-42796911043b@kernel.org [2] https://lore.kernel.org/20261015-urgent_fixes-v1-6-42796911043b@kernel.org [3] https://lore.kernel.org/20261027-fixes_core-v1-23-6f74bec9a5bb@kernel.org (v1, now 23/47 in v2) Jose A. Perez de Azpillaga (2): mm/userfaultfd: recheck WP registration in the hugetlb UFFDIO_COPY retry selftests/mm: add a uffd test for re-registering during UFFDIO_COPY mm/userfaultfd.c | 4 + tools/testing/selftests/mm/uffd-unit-tests.c | 105 +++++++++++++++++++ 2 files changed, 109 insertions(+) base-commit: 24d45a1475dd4c671feb1df705f67ef2fc293969 -- 2.55.0