From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id B319C3A3E79; Fri, 3 Jul 2026 11:42:54 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783078976; cv=none; b=kgbMraS8sf4OEYDOl8BeAtsVj4FGQ/cGTI5HDAw4TGzvADpGlCTVeemuvdye6WlN4bvEHI/SO4X5/WKYEhWGgcJ8DJsPpkSEu/5nsktfERDShLCHTUw6v8KjgnSRJLotJvzvoozUzC6wLH2tg94EzJraIrCaMiq/X02W7vMp46w= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783078976; c=relaxed/simple; bh=h1IY5vXGtS5qm0GLFc9NhQBQjfsdy191rN1Uth+Oiss=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=tEGbewGmj3xtxdIdELxOWPztwBBvnmxmNV6tySk/13e67vOzs25Of659D8y2v96ah143ZpuINt2/EDY/EQ8pcoqIf3GbeATAW0n/szcB18aXmRKM2wQkeB6VkCONrY4HfJr9+ld0hakVDBYv341xIVvDYLMV1a6UKCZsc+yGaeM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b=k2n+xkzc; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b="k2n+xkzc" Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id B647C361C; Fri, 3 Jul 2026 04:42:49 -0700 (PDT) Received: from cesw-amp-gbt-1s-m12830-01.blr.arm.com (cesw-amp-gbt-1s-m12830-01.blr.arm.com [10.164.195.31]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id 934E83FAA1; Fri, 3 Jul 2026 04:42:44 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1783078974; bh=h1IY5vXGtS5qm0GLFc9NhQBQjfsdy191rN1Uth+Oiss=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=k2n+xkzcwCyd3J/xSa4zKVaUpOHOy35BxeWEYAFbGOCKUM0tXaNOstPt5Q76BSk3n yjtzVV2etNN40/5idIaXRjsy/phcdoOXCHriXGcjm3ZFmeV1EARux/ZHb42t7GgVAC OzlyxC0kw2XvxGBk6gm4fmcJpkt6Hip6x3aoeeAQ= From: Dev Jain To: muchun.song@linux.dev, osalvador@suse.de, akpm@linux-foundation.org, ljs@kernel.org, david@kernel.org, liam@infradead.org Cc: Dev Jain , riel@surriel.com, vbabka@kernel.org, harry@kernel.org, jannh@google.com, lance.yang@linux.dev, kas@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, apopple@nvidia.com, rcampbell@nvidia.com, ziy@nvidia.com, matthew.brost@intel.com, joshua.hahnjy@gmail.com, rakie.kim@sk.com, byungchul@sk.com, gourry@gourry.net, ying.huang@linux.alibaba.com, ak@linux.intel.com, nao.horiguchi@gmail.com, mel@csn.ul.ie, j-nomura@ce.jp.nec.com, pfalcato@suse.de, tglx@kernel.org, dave.hansen@intel.com, jpoimboe@kernel.org, catalin.marinas@arm.com, will@kernel.org, linux-arm-kernel@lists.infradead.org, ryan.roberts@arm.com, anshuman.khandual@arm.com, stable@vger.kernel.org Subject: [PATCH v3 3/6] mm/rmap: use huge_ptep_get() in try_to_migrate_one() Date: Fri, 3 Jul 2026 11:41:56 +0000 Message-ID: <20260703114202.365553-4-dev.jain@arm.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260703114202.365553-1-dev.jain@arm.com> References: <20260703114202.365553-1-dev.jain@arm.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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. Fixes: a98a2f0c8ce1 ("mm/rmap: split migration into its own function") Cc: stable@vger.kernel.org Acked-by: Muchun Song Signed-off-by: Dev Jain --- mm/rmap.c | 16 ++++++++++------ 1 file changed, 10 insertions(+), 6 deletions(-) diff --git a/mm/rmap.c b/mm/rmap.c index 03737daa348c0..ea4ad5e662f7d 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -2505,14 +2505,19 @@ 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); @@ -2520,7 +2525,6 @@ 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); -- 2.43.0