The patch titled Subject: mm/damon/ops-common: ignore migration request to invalid nodes has been added to the -mm mm-unstable branch. Its filename is mm-damon-ops-common-ignore-migration-request-to-invalid-nodes.patch

This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches...

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: SeongJae Park sj@kernel.org Subject: mm/damon/ops-common: ignore migration request to invalid nodes Date: Sun, 20 Jul 2025 11:58:22 -0700

damon_migrate_pages() tries migration even if the target node is invalid. If users mistakenly make such invalid requests via DAMOS_MIGRATE_{HOT,COLD} action, the below kernel BUG can happen.

[ 7831.883495] BUG: unable to handle page fault for address: 0000000000001f48 [ 7831.884160] #PF: supervisor read access in kernel mode [ 7831.884681] #PF: error_code(0x0000) - not-present page [ 7831.885203] PGD 0 P4D 0 [ 7831.885468] Oops: Oops: 0000 [#1] SMP PTI [ 7831.885852] CPU: 31 UID: 0 PID: 94202 Comm: kdamond.0 Not tainted 6.16.0-rc5-mm-new-damon+ #93 PREEMPT(voluntary) [ 7831.886913] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-4.el9 04/01/2014 [ 7831.887777] RIP: 0010:__alloc_frozen_pages_noprof (include/linux/mmzone.h:1724 include/linux/mmzone.h:1750 mm/page_alloc.c:4936 mm/page_alloc.c:5137) [...] [ 7831.895953] Call Trace: [ 7831.896195] <TASK> [ 7831.896397] __folio_alloc_noprof (mm/page_alloc.c:5183 mm/page_alloc.c:5192) [ 7831.896787] migrate_pages_batch (mm/migrate.c:1189 mm/migrate.c:1851) [ 7831.897228] ? __pfx_alloc_migration_target (mm/migrate.c:2137) [ 7831.897735] migrate_pages (mm/migrate.c:2078) [ 7831.898141] ? __pfx_alloc_migration_target (mm/migrate.c:2137) [ 7831.898664] damon_migrate_folio_list (mm/damon/ops-common.c:321 mm/damon/ops-common.c:354) [ 7831.899140] damon_migrate_pages (mm/damon/ops-common.c:405) [...]

Add a target node validity check in damon_migrate_pages(). The validity check is stolen from that of do_pages_move(), which is being used for the move_pages() system call.

Link: https://lkml.kernel.org/r/20250720185822.1451-1-sj@kernel.org Fixes: b51820ebea65 ("mm/damon/paddr: introduce DAMOS_MIGRATE_COLD action for demotion") [6.11.x] Signed-off-by: SeongJae Park sj@kernel.org Reviewed-by: Joshua Hahn joshua.hahnjy@gmail.com Cc: Honggyu Kim honggyu.kim@sk.com Cc: Hyeongtak Ji hyeongtak.ji@sk.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---

mm/damon/ops-common.c | 4 ++++ 1 file changed, 4 insertions(+)

--- a/mm/damon/ops-common.c~mm-damon-ops-common-ignore-migration-request-to-invalid-nodes +++ a/mm/damon/ops-common.c @@ -383,6 +383,10 @@ unsigned long damon_migrate_pages(struct if (list_empty(folio_list)) return nr_migrated;

+ if (target_nid < 0 || target_nid >= MAX_NUMNODES || + !node_state(target_nid, N_MEMORY)) + return nr_migrated; + noreclaim_flag = memalloc_noreclaim_save();

nid = folio_nid(lru_to_folio(folio_list)); _

Patches currently in -mm which might be from sj@kernel.org are

mm-damon-core-commit-damos_quota_goal-nid.patch mm-damon-sysfs-implement-refresh_ms-file-under-kdamond-directory.patch mm-damon-sysfs-implement-refresh_ms-file-internal-work.patch docs-admin-guide-mm-damon-usage-document-refresh_ms-file.patch docs-abi-damon-update-for-refresh_ms.patch mm-damon-ops-common-ignore-migration-request-to-invalid-nodes.patch