From mboxrd@z Thu Jan 1 00:00:00 1970 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 34A7251FCBF for ; Fri, 4 Sep 2026 18:35:33 +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=1788546938; cv=none; b=MDtttvM8P1b6DqE6if1z5APGxsFQxRtc/+AEvOX6Z8/9/DnFx2XQbB1le5eiT+PVyG4urY+Eveeo99KRtnFpzpwEenlaoUk5WDUNvAmXWgY3y0WmTDgDIJyco7GzbXeRXvYmdriDM2ZOlwJYCLxe4Tl7aGN+1nqinEjUuMbteWs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788546938; c=relaxed/simple; bh=edcinFq0RJtKC0lx3aMpJEXiSTCZrmZr/1XmZHta0ks=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=U+OmP6j7k8RsC2GlErd54xxbrVXziElipMvdn/p3B5hKnQLFcEm06VnwfC5rrayOWuf/MXehSJ1RQMs4zmq/pKB4u8fNd/AG794PArNUW4THf4HRnBbe3RP2aUyCmdgXex8D5HH1Ahw9ULlKljWj48YKF9Vx8HXz+yNib5xYub0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=HLjMKucF; 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="HLjMKucF" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 641251F00A3E; Fri, 4 Sep 2026 18:35:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788546929; bh=HxuRhjJvQyMoYF7eFetg5twNaKvoLk16DViePmIV6dY=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=HLjMKucF7IZa/BbO6qLq6oCCLpUzDg+4ET+4ukn3qIftKIALF63B/CyfZ0rFilzAS d16kHLP5olR2hxlyC0bbX2TLg3WzsdYkks1+7o/YsjJEihzrT5iGC0iyKdZjm0wYPQ v7Z5ehbqvkjuLrxrLLtHlzZWhA/Mq2cmvGBHf9No/X83wKhvnQ+Jwe0BCQC09dzzsN M+pYmTboIYoJkUs/ysFED4pgQtHHHqKK9Q6pIrNdCtLLXBkioIbUMC5dl7cXOSLqHm 0W+DZGRxZ+0+Sm7EmSxyQTJxG0L1ppaOocivXY2nQ9q20XWvz36AmCSePBTnFUz9kU POofMQhKfRIhA== 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 5.15.y] mm/rmap: use huge_ptep_get() in try_to_migrate_one() Date: Fri, 4 Sep 2026 14:35:24 -0400 Message-ID: <20260904183524.1324443-1-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <2026090300-awry-struggle-b110@gregkh> References: <2026090300-awry-struggle-b110@gregkh> 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 [ guarded huge_ptep_get() usage with CONFIG_HUGETLB_PAGE for HugeTLB-disabled builds. ] Signed-off-by: Sasha Levin --- mm/rmap.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/mm/rmap.c b/mm/rmap.c index c103e01d22327..9fd5422672805 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -1784,7 +1784,11 @@ static bool try_to_migrate_one(struct page *page, struct vm_area_struct *vma, /* Unexpected PMD-mapped THP? */ VM_BUG_ON_PAGE(!pvmw.pte, page); - subpage = page - page_to_pfn(page) + pte_pfn(*pvmw.pte); + if (PageHuge(page)) + pteval = huge_ptep_get(pvmw.pte); + else + pteval = *pvmw.pte; + subpage = page - page_to_pfn(page) + pte_pfn(pteval); address = pvmw.address; if (PageHuge(page) && !PageAnon(page)) { -- 2.53.0