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Wed, 8 Jul 2026 08:30:52 +0800 (CST) Received: from dggpemf100008.china.huawei.com (unknown [7.185.36.138]) by mail.maildlp.com (Postfix) with ESMTPS id 3F23B402AB; Wed, 8 Jul 2026 08:40:09 +0800 (CST) Received: from localhost.localdomain (10.50.87.83) by dggpemf100008.china.huawei.com (7.185.36.138) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1544.11; Wed, 8 Jul 2026 08:40:08 +0800 From: Kefeng Wang To: Andrew Morton , David Hildenbrand CC: Zi Yan , Matthew Brost , Joshua Hahn , Rakie Kim , Byungchul Park , Gregory Price , Ying Huang , Alistair Popple , , Kefeng Wang , Subject: [PATCH v2] mm: migrate_device: fix pte_pfn/pte_dirty called on non-present PTE Date: Wed, 8 Jul 2026 08:39:55 +0800 Message-ID: <20260708003955.4024340-1-wangkefeng.wang@huawei.com> X-Mailer: git-send-email 2.27.0 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain X-Originating-IP: [10.50.87.83] X-ClientProxiedBy: kwepems500002.china.huawei.com (7.221.188.17) To dggpemf100008.china.huawei.com (7.185.36.138) X-Stat-Signature: 8qizpd7owjbxf9x69ijzddcsq9b1mjq8 X-Rspamd-Queue-Id: 8D5DA20006 X-Rspam-User: X-Rspamd-Server: rspam07 X-HE-Tag: 1783471214-69302 X-HE-Meta: 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 agRy/Epp VwkZuSObwEWetvNSxLZYdpqUfn8CtzQYiZ1GhkJ6NdVT9atFqQMEwUH1zSWRwFx5SU+Tr/v011uglSR1QgHnc52Alo/dTPpQpJaSQXbZodhd88Y7sv3bCcAMRm7XmkLvBpSYRdv/l3s2vL2KfmKBObZ9Vf0mUBwMafjE2fWO0lpelzNGoE1NU/zgceltC/mCXK2I1ipq9L/ip75lyfyHuJytvq7S+MU1b+B0G8bxktLxNwpq4ybM1ec3qxiOfM2UTMszVTdb+jRzxv2lFVtBXaYHN9eVwzGecLTcVjLuJ3ZnB9SpDUExDwdSgKyUPDW53cuqexN8BkTYPi7LX4RuovCI3IzPy6emYvBqQ6jLcoT/9IuOnCLx3SKePAwjqOPXA9xcrBlDD2jg+c0W4R5eVf/3JG/t69cmZR53GgLUEB8B435Ht0RDmn//Z+g== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: pte_pfn() and pte_dirty() have undefined behaviour when called on a non-present PTE. In migrate_vma_collect_pmd(), these functions may be invoked on non-present entries (e.g., device-private entries), leading to potential crashes from pte_pfn() or incorrect dirty folio accounting from pte_dirty(). Fix both by guarding with pte_present() checks. Fixes: fd35ca3d12cc ("mm/migrate_device.c: copy pte dirty bit to page") Fixes: 6c287605fd56 ("mm: remember exclusively mapped anonymous pages with PG_anon_exclusive") Cc: Signed-off-by: Kefeng Wang --- v2: - correct changelog and Fixes tags, suggested by David. - cc stable, suggested by Andrew. mm/migrate_device.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/mm/migrate_device.c b/mm/migrate_device.c index 052167f9ad54..6e711381f092 100644 --- a/mm/migrate_device.c +++ b/mm/migrate_device.c @@ -411,7 +411,8 @@ static int migrate_vma_collect_pmd(pmd_t *pmdp, bool anon_exclusive; pte_t swp_pte; - flush_cache_page(vma, addr, pte_pfn(pte)); + if (pte_present(pte)) + flush_cache_page(vma, addr, pte_pfn(pte)); anon_exclusive = folio_test_anon(folio) && PageAnonExclusive(page); if (anon_exclusive) { @@ -432,7 +433,7 @@ static int migrate_vma_collect_pmd(pmd_t *pmdp, migrate->cpages++; /* Set the dirty flag on the folio now the pte is gone. */ - if (pte_dirty(pte)) + if (pte_present(pte) && pte_dirty(pte)) folio_mark_dirty(folio); /* Setup special migration page table entry */ -- 2.27.0