Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 490513ADBA7 for ; Fri, 4 Sep 2026 03:02:44 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788490967; cv=none; b=nppmbqgI9ucEtu5lkNgrgdeCYqvZOhr8Y8JalyH4vJJpSKLpz/4/PnOTclWb+/d0Sk7eU8LRuqflrtF7CuoFNhLzynl63i+lWBUCa3xXv4c/pPy3QMwCadHC9nYrFx7xjogDW470x1GZfpkRxfJwtt4LGQXCAbq6T+tBtmZc1W8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788490967; c=relaxed/simple; bh=n6bHbFGymYJwfNSe8EF4onSglfCM22g+LVQOF3Zn95A=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=jy/BGwQ47rBnHu2v1Jgwyjp8sa+BDv0Q0igGs6/2gYEDkd5YiMH0MM5nUBafthMIJn/wyX6wXwQLuFXIhjTHmPzWxPDHPsPFqLlr22y2RNlcuGhb8tdY24zRLeCEwhJz0zSiKsMLDm1fIcnk8BVQ0vr0g5UESWCbWtNVuqwuoVQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Soll3y9v; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="Soll3y9v" Received: by smtp.kernel.org (Postfix) with ESMTPSA id F11E71F00ACF; Fri, 4 Sep 2026 03:02:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788490964; bh=SqLhG5y0bvGalE/AfhZjX9bodL4o6mGyar8plcm8hEo=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=Soll3y9vbQNmWlSwv280Est2KzYMGJVzq2lGWTRrEihew3f9xlLbkIKcBKCeI1kQU +EEkVz25uG6GBnrMkaQdZzqDVI0cHcWey6/sQdPtcNpeFATimRoVhLNKi/58gjUZNt gwwCU3UkXDb5X7GKM0+gOnRe04DgM1YRe+wHH81FrfsZF9+gzqaUmiW1xcSqY5TJ4B 3l/XLDOXmRQcgAXLvgDMAbxrCe/9BybDwyheootHEbKrDTcPB17YAIu6b36Ik9Puhj DbAZCfylXBg+K5GOiMmwm6tdByycPeMcQ1sMl7JKwmk+VtyhFIXQVvzMDFuKnhmOM/ 2J77G3coxtE3w== From: Sasha Levin To: stable@vger.kernel.org Cc: Dev Jain , Muchun Song , "David Hildenbrand (Arm)" , Alistair Popple , Andi Kleen , Anshuman Khandual , Byungchul Park , Catalin Marinas , Dave Hansen , Gregory Price , Harry Yoo , "Huang, Ying" , Jann Horn , Josh Poimboeuf , Joshua Hahn , Kiryl Shutsemau , Lance Yang , "Liam R. Howlett" , Lorenzo Stoakes , Matthew Brost , Mel Gorman , Naoya Horiguchi , Oscar Salvador , Pedro Falcato , Rakie Kim , Ralph Campbell , Rik van Riel , Ryan Roberts , Vlastimil Babka , Will Deacon , Zi Yan , Andrew Morton , Sasha Levin Subject: [PATCH 6.12.y 2/2] mm/rmap: use huge_ptep_get() in try_to_migrate_one() Date: Thu, 3 Sep 2026 23:02:33 -0400 Message-ID: <20260904030233.2306854-2-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260904030233.2306854-1-sashal@kernel.org> References: <2026090358-glandular-hardiness-9af2@gregkh> <20260904030233.2306854-1-sashal@kernel.org> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Dev Jain [ Upstream commit 9be12ffa78cd087d41086f937a156435d4e588e9 ] try_to_migrate_one() is used by folio migration to replace a present mapping with a migration entry. For hugetlb folios, page_vma_mapped_walk() returns the pte pointer to the hugetlb folio in pvmw.pte, but the code reads the huge pte entry with ptep_get(). On arches which provide their own huge_ptep_get() to dereference a huge pte pointer, accessing via ptep_get() would cause pte_pfn(), pte_present() etc to misbehave. It is not clear whether this has a trivially visible effect to userspace. Use huge_ptep_get() to dereference a huge pte pointer. Commit a98a2f0c8ce1 copied the bug from try_to_unmap_one into try_to_migrate_one. [akpm@linux-foundation.org: coding-style cleanups] Link: https://lore.kernel.org/20260703114202.365553-4-dev.jain@arm.com Fixes: a98a2f0c8ce1 ("mm/rmap: split migration into its own function") Signed-off-by: Dev Jain Acked-by: Muchun Song Acked-by: David Hildenbrand (Arm) Cc: Alistair Popple Cc: Andi Kleen Cc: Anshuman Khandual Cc: Byungchul Park Cc: Catalin Marinas Cc: Dave Hansen Cc: Gregory Price Cc: Harry Yoo Cc: "Huang, Ying" Cc: Jann Horn Cc: Josh Poimboeuf Cc: Joshua Hahn Cc: Jun'ichi "Nick" Nomura Cc: Kiryl Shutsemau Cc: Lance Yang Cc: Liam R. Howlett Cc: Lorenzo Stoakes Cc: Matthew Brost Cc: Mel Gorman Cc: Naoya Horiguchi Cc: Oscar Salvador Cc: Pedro Falcato Cc: Rakie Kim Cc: Ralph Campbell Cc: Rik van Riel Cc: Ryan Roberts Cc: Vlastimil Babka Cc: Will Deacon Cc: Zi Yan Cc: Signed-off-by: Andrew Morton Signed-off-by: Sasha Levin --- mm/rmap.c | 15 +++++++++------ 1 file changed, 9 insertions(+), 6 deletions(-) diff --git a/mm/rmap.c b/mm/rmap.c index 36a2e0eb8be48..be105a7d2eaa3 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -2070,14 +2070,18 @@ static bool try_to_migrate_one(struct folio *folio, struct vm_area_struct *vma, /* Unexpected PMD-mapped THP? */ VM_BUG_ON_FOLIO(!pvmw.pte, folio); - /* - * Handle PFN swap PTEs, such as device-exclusive ones, that - * actually map pages. - */ - pteval = ptep_get(pvmw.pte); + address = pvmw.address; + if (folio_test_hugetlb(folio)) + pteval = huge_ptep_get(mm, address, pvmw.pte); + else + pteval = ptep_get(pvmw.pte); if (likely(pte_present(pteval))) { pfn = pte_pfn(pteval); } else { + /* + * Handle PFN swap PTEs, such as device-exclusive ones, + * that actually map pages. + */ const softleaf_t entry = softleaf_from_pte(pteval); pfn = softleaf_to_pfn(entry); @@ -2085,7 +2089,6 @@ static bool try_to_migrate_one(struct folio *folio, struct vm_area_struct *vma, } subpage = folio_page(folio, pfn - folio_pfn(folio)); - address = pvmw.address; anon_exclusive = folio_test_anon(folio) && PageAnonExclusive(subpage); -- 2.53.0