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b=Z/wWLwah4Li5c+pfrKApTo5VXzHxfARVihf4AGVCD3RuuhwAj3rtImIwXRqVIk9VJ bSzQcZRYsrg7fZWOcGarXnwD2+cP/KgFD8iq4ox1wcHHZoK4FD/dFa6oxFwn4yaScL rzSEL+bVcdeNocSoqrv4Ci5FRk5Cs06R48x8otlYn5WKb+ZlXz74NwJ7htNa5HFk2/ 2eDV/0CUMiZ4lbc9gY7W87l1urHZP0Wx3WrrFwnFTYCefnowfIWbS3p8Ab9mtR8oBl hRbmX+v9wQbuguQb7GnHUSL0hZV8GsOUEjtUIOEGCMDmnn7GUQTJ9n/pAIzhOT/1fJ ZrwIrY/rhClmA== From: Sasha Levin To: akpm@linux-foundation.org Cc: david@redhat.com, surenb@google.com, aarcange@redhat.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Sasha Levin Subject: [PATCH] mm/userfaultfd: fix kmap_local LIFO ordering for CONFIG_HIGHPTE Date: Thu, 31 Jul 2025 10:44:31 -0400 Message-Id: <20250731144431.773923-1-sashal@kernel.org> X-Mailer: git-send-email 2.39.5 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: C02FA1C0003 X-Stat-Signature: tccnmzjhykw3f38bbqzr14xp7mmuwphh X-Rspam-User: X-Rspamd-Server: rspam07 X-HE-Tag: 1753973076-507220 X-HE-Meta: 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 haAluaXk GO5N57ggt6gayiQxnNK3KhppgcIXfFbYGkxg8sE13UT8w98uQGh+/0C+fjyQ48bKobtncW/y6favw6GdAlmmjXfnlQMus7QV5iUakAby+KwRVE4baiX+lSKOrseFEd6OWp7sm6JAgEXCh04RaCmAF7n+wS7k9R+SI2V9Rlr6WbgmmKwxroVSkBg9PBGH6uw4ypQsOi7S6jSEUQofw+iqU2zO2psn4hEfmSPLdzrGRLWjY1NLogtq8o9Eg3TIEws5UNED8mjnXQhPO2kJ2mr3LHBRmPJHqyBIL1l3ALLE+iHJqInAXVE3nkIbvFqpvG9n0g/Si X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: With CONFIG_HIGHPTE on 32-bit ARM, move_pages_pte() maps PTE pages using kmap_local_page(), which requires unmapping in Last-In-First-Out order. The current code maps dst_pte first, then src_pte, but unmaps them in the same order (dst_pte, src_pte), violating the LIFO requirement. This causes the warning in kunmap_local_indexed(): WARNING: CPU: 0 PID: 604 at mm/highmem.c:622 kunmap_local_indexed+0x178/0x17c addr \!= __fix_to_virt(FIX_KMAP_BEGIN + idx) Fix this by reversing the unmap order to respect LIFO ordering. This issue follows the same pattern as similar fixes: - commit eca6828403b8 ("crypto: skcipher - fix mismatch between mapping and unmapping order") - commit 8cf57c6df818 ("nilfs2: eliminate staggered calls to kunmap in nilfs_rename") Both of which addressed the same fundamental requirement that kmap_local operations must follow LIFO ordering. Fixes: adef440691ba ("userfaultfd: UFFDIO_MOVE uABI") Co-developed-by: Claude claude-opus-4-20250514 Signed-off-by: Sasha Levin Acked-by: David Hildenbrand Reviewed-by: Suren Baghdasaryan --- mm/userfaultfd.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c index 8253978ee0fb..bf7a57ea71e0 100644 --- a/mm/userfaultfd.c +++ b/mm/userfaultfd.c @@ -1453,10 +1453,15 @@ static int move_pages_pte(struct mm_struct *mm, pmd_t *dst_pmd, pmd_t *src_pmd, folio_unlock(src_folio); folio_put(src_folio); } - if (dst_pte) - pte_unmap(dst_pte); + /* + * Unmap in reverse order (LIFO) to maintain proper kmap_local + * index ordering when CONFIG_HIGHPTE is enabled. We mapped dst_pte + * first, then src_pte, so we must unmap src_pte first, then dst_pte. + */ if (src_pte) pte_unmap(src_pte); + if (dst_pte) + pte_unmap(dst_pte); mmu_notifier_invalidate_range_end(&range); if (si) put_swap_device(si); -- 2.39.5