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 E1E593DA7F2; Thu, 25 Jun 2026 11:30:29 +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=1782387031; cv=none; b=tycARA2G13XfnP109i7HqHDZ5G3eOfcbNDtQdRSK8wwvwwcyWjl9DQgtRzBsMY/RDPQXzCUjVH537Ouam6Nwo78oW6Pnjfr12r3PjGcpHjADXNTd2biMbpizIy/CgkuQmIZaECwwtseFJuB9z0d8Fvml8v6SCNmKCRRSBYWjCWE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782387031; c=relaxed/simple; bh=Ib8HLtVOx0bEstNiQgQ183JVLf7OFocK8ZFR9pqwh+c=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=F7LqmA+JShl1l44LdSql+SyvNBv8xPE4CYHqlHbTwhr5cmDFnWOCqytpyy0eaOJIafOjKpz4A8M/dJQe1H0ghhGfvRoCmubnmzWjeuDm+jimfmfaaN5NjMHlnQmlzRijukZMemgj15jeL/U2a/eLgb3RTQaDOgO/f6KN58umHWw= 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=D00yAIF3; 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="D00yAIF3" 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 C3321328E; Thu, 25 Jun 2026 04:30:24 -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 72CE23F62B; Thu, 25 Jun 2026 04:30:20 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1782387029; bh=Ib8HLtVOx0bEstNiQgQ183JVLf7OFocK8ZFR9pqwh+c=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=D00yAIF3PxWlFQ7TUPdyDv/Bkj2YGFHDJzLdp6WtkJ3941gqW0Tlc5PQ77i3EdsD0 wW2iicZugLsxvqgCZ0MbrOxkaRuVF7sbD2nf3gU665s+IsSrXI2sKFC4bK0LQgm5rT TAdYoJBI2FPE0WKowUceZqoHbAKlu0CKJgr37Kho= 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, rcampbell@nvidia.com, apopple@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, mel@csn.ul.ie, nao.horiguchi@gmail.com, ak@linux.intel.com, j-nomura@ce.jp.nec.com, pfalcato@suse.de, dave.hansen@intel.com, tglx@kernel.org, jpoimboe@kernel.org, ryan.roberts@arm.com, anshuman.khandual@arm.com, stable@vger.kernel.org Subject: [PATCH 2/5] mm/rmap: use huge_ptep_get() in try_to_migrate_one() Date: Thu, 25 Jun 2026 11:29:51 +0000 Message-ID: <20260625112955.3254283-3-dev.jain@arm.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260625112955.3254283-1-dev.jain@arm.com> References: <20260625112955.3254283-1-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 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 aa8a254efaecc..abc3a44baaa3d 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -2505,11 +2505,16 @@ 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 { + /* + * Handle PFN swap PTEs, such as device-exclusive ones, + * that actually map pages. + */ + pteval = ptep_get(pvmw.pte); + } if (likely(pte_present(pteval))) { pfn = pte_pfn(pteval); } else { @@ -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