+ mm-migrate_device-move-softleaf_to_folio-inside-device-private-branch.patch added to mm-unstable branch

+ mm-migrate_device-move-softleaf_to_folio-inside-device-private-branch.patch added to mm-unstable branch

[Andrew Morton]

The patch titled
     Subject: mm/migrate_device: move softleaf_to_folio() inside device-private branch
has been added to the -mm mm-unstable branch.  Its filename is
     mm-migrate_device-move-softleaf_to_folio-inside-device-private-branch.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-migrate_device-move-softleaf_to_folio-inside-device-private-branch.patch

This patch will later appear in the mm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Usama Arif <usama.arif@linux.dev>
Subject: mm/migrate_device: move softleaf_to_folio() inside device-private branch
Date: Mon, 6 Jul 2026 04:42:07 -0700

migrate_vma_collect_pmd() calls softleaf_to_folio() on a non-present PMD
before checking the entry's type.  softleaf_to_folio() converts the
entry's offset to a PFN, which is only meaningful for migration or
device-private entries.

A PMD swap entry's offset is a swap offset, not a PFN, so the lookup would
either return a bogus folio pointer or trip pfn_to_page validation on a
debug kernel.  In the non-device-private path the returned folio is then
unused (the OR short-circuits to migrate_vma_collect_skip()), but the
lookup itself is already unsafe.

Move the softleaf_to_folio() call inside the device-private branch where
the folio is actually needed, mirroring the equivalent
change_non_present_huge_pmd() fix.

Link: https://lore.kernel.org/20260706114320.1643046-6-usama.arif@linux.dev
Signed-off-by: Usama Arif <usama.arif@linux.dev>
Reviewed-by: Zi Yan <ziy@nvidia.com>
Acked-by: David Hildenbrand (Arm) <david@kernel.org>
Cc: Alexandre Ghiti <alex@ghiti.fr>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Baoquan He <baoquan.he@linux.dev>
Cc: Barry Song <baohua@kernel.org>
Cc: Chris Li <chrisl@kernel.org>
Cc: Dev Jain <dev.jain@arm.com>
Cc: "Huang, Ying" <ying.huang@linux.alibaba.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Kairui Song <kasong@tencent.com>
Cc: Kemeng Shi <shikemeng@huaweicloud.com>
Cc: Kiryl Shutsemau <kas@kernel.org>
Cc: Lance Yang <lance.yang@linux.dev>
Cc: Liam R. Howlett <liam@infradead.org>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Nico Pache <npache@redhat.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Vlastimil Babka <vbabka@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/migrate_device.c |   11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

--- a/mm/migrate_device.c~mm-migrate_device-move-softleaf_to_folio-inside-device-private-branch
+++ a/mm/migrate_device.c
@@ -166,11 +166,14 @@ static int migrate_vma_collect_huge_pmd(
 	} else if (!pmd_present(*pmdp)) {
 		const softleaf_t entry = softleaf_from_pmd(*pmdp);
 
-		folio = softleaf_to_folio(entry);
-
 		if (!softleaf_is_device_private(entry) ||
-			!(migrate->flags & MIGRATE_VMA_SELECT_DEVICE_PRIVATE) ||
-			(folio->pgmap->owner != migrate->pgmap_owner)) {
+		    !(migrate->flags & MIGRATE_VMA_SELECT_DEVICE_PRIVATE)) {
+			spin_unlock(ptl);
+			return migrate_vma_collect_skip(start, end, walk);
+		}
+
+		folio = softleaf_to_folio(entry);
+		if (folio->pgmap->owner != migrate->pgmap_owner) {
 			spin_unlock(ptl);
 			return migrate_vma_collect_skip(start, end, walk);
 		}
_

Patches currently in -mm which might be from usama.arif@linux.dev are

userfaultfd-wait-on-source-pmd-during-uffdio_move.patch
mm-swap_state-remove-unnecessary-lru_add_drain-from-readahead.patch
mm-add-softleaf_to_pmd-and-convert-existing-callers.patch
mm-extract-mm_prepare_for_swap_entries-helper.patch
fs-proc-use-softleaf_has_pfn-in-pagemap-pmd-walker.patch
mm-huge_memory-move-softleaf_to_folio-inside-migration-branch.patch
mm-migrate_device-move-softleaf_to_folio-inside-device-private-branch.patch
mm-rename-arch_enable_thp_migration-to-arch_has_pmd_softleaves.patch
mm-vmpressure-skip-tree=true-accounting-on-cgroup-v2.patch
mm-vmpressure-skip-tree=true-accounting-on-cgroup-v2-fix.patch
mm-vmpressure-move-v1-userspace-eventfd-code-into-memcontrol-v1c.patch
mm-migrate_device-pin-large-folios-before-splitting.patch
mm-migrate_device-pin-large-folios-before-splitting-fix.patch