+ samples-damon-mtier-support-boot-time-enable-setup.patch added to mm-new branch

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

The patch titled
     Subject: samples/damon/mtier: support boot time enable setup
has been added to the -mm mm-new branch.  Its filename is
     samples-damon-mtier-support-boot-time-enable-setup.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/samples-damon-mtier-support-boot-time-enable-setup.patch

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

Note, mm-new is a provisional staging ground for work-in-progress
patches, and acceptance into mm-new is a notification for others take
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------------------------------------------------------
From: SeongJae Park <sj@kernel.org>
Subject: samples/damon/mtier: support boot time enable setup
Date: Sun, 6 Jul 2025 12:32:04 -0700

If 'enable' parameter of the 'mtier' DAMON sample module is set at boot
time via the kernel command line, memory allocation is tried before the
slab is initialized.  As a result kernel NULL pointer dereference BUG can
happen.  Fix it by checking the initialization status.

Link: https://lkml.kernel.org/r/20250706193207.39810-4-sj@kernel.org
Fixes: 82a08bde3cf7 ("samples/damon: implement a DAMON module for memory tiering")
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 samples/damon/mtier.c |   13 +++++++++++++
 1 file changed, 13 insertions(+)

--- a/samples/damon/mtier.c~samples-damon-mtier-support-boot-time-enable-setup
+++ a/samples/damon/mtier.c
@@ -157,6 +157,8 @@ static void damon_sample_mtier_stop(void
 	damon_destroy_ctx(ctxs[1]);
 }
 
+static bool init_called;
+
 static int damon_sample_mtier_enable_store(
 		const char *val, const struct kernel_param *kp)
 {
@@ -170,6 +172,9 @@ static int damon_sample_mtier_enable_sto
 	if (enable == enabled)
 		return 0;
 
+	if (!init_called)
+		return 0;
+
 	if (enable) {
 		err = damon_sample_mtier_start();
 		if (err)
@@ -182,6 +187,14 @@ static int damon_sample_mtier_enable_sto
 
 static int __init damon_sample_mtier_init(void)
 {
+	int err = 0;
+
+	init_called = true;
+	if (enable) {
+		err = damon_sample_mtier_start();
+		if (err)
+			enable = false;
+	}
 	return 0;
 }
 
_

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

mm-damon-core-handle-damon_call_control-as-normal-under-kdmond-deactivation.patch
mm-damon-introduce-damon_stat-module.patch
mm-damon-introduce-damon_stat-module-fix.patch
mm-damon-stat-calculate-and-expose-estimated-memory-bandwidth.patch
mm-damon-stat-calculate-and-expose-idle-time-percentiles.patch
docs-admin-guide-mm-damon-add-damon_stat-usage-document.patch
mm-damon-paddr-use-alloc_migartion_target-with-no-migration-fallback-nodemask.patch
revert-mm-rename-alloc_demote_folio-to-alloc_migrate_folio.patch
revert-mm-make-alloc_demote_folio-externally-invokable-for-migration.patch
selftets-damon-add-a-test-for-memcg_path-leak.patch
mm-damon-sysfs-schemes-decouple-from-damos_quota_goal_metric.patch
mm-damon-sysfs-schemes-decouple-from-damos_action.patch
mm-damon-sysfs-schemes-decouple-from-damos_wmark_metric.patch
mm-damon-sysfs-schemes-decouple-from-damos_filter_type.patch
mm-damon-sysfs-decouple-from-damon_ops_id.patch
selftests-damon-add-drgn-script-for-extracting-damon-status.patch
selftests-damon-_damon_sysfs-set-kdamondpid-in-start.patch
selftests-damon-add-python-and-drgn-based-damon-sysfs-test.patch
selftests-damon-sysfspy-test-monitoring-attribute-parameters.patch
selftests-damon-sysfspy-test-adaptive-targets-parameter.patch
selftests-damon-sysfspy-test-damos-schemes-parameters-setup.patch
mm-damon-add-trace-event-for-auto-tuned-monitoring-intervals.patch
mm-damon-add-trace-event-for-effective-size-quota.patch
samples-damon-wsse-fix-boot-time-enable-handling.patch
samples-damon-prcl-fix-boot-time-enable-crash.patch
samples-damon-mtier-support-boot-time-enable-setup.patch
mm-damon-reclaim-reset-enabled-when-damon-start-failed.patch
mm-damon-lru_sort-reset-enabled-when-damon-start-failed.patch
mm-damon-reclaim-use-parameter-context-correctly.patch