+ mm-damon-ops-common-ignore-migration-request-to-invalid-nodes.patch added to mm-unstable branch

[Andrew Morton <akpm@linux-foundation.org>]

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/mm-damon-ops-common-ignore-migration-request-to-invalid-nodes.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: 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