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

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

[Andrew Morton]

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
notice and to finish up reviews.  Please do not hesitate to respond to
review feedback and post updated versions to replace or incrementally
fixup patches in mm-new.

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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