From: SeongJae Park <sj@kernel.org>
Date: Sun, 6 Jul 2025 19:32:04 +0000 (-0700)
Subject: samples/damon/mtier: support boot time enable setup
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=964314344eab7bc43e38a32be281c5ea0609773b;p=thirdparty%2Fkernel%2Flinux.git

samples/damon/mtier: support boot time enable setup

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>
---

diff --git a/samples/damon/mtier.c b/samples/damon/mtier.c
index 97892ade7f313..bc9d8195da873 100644
--- a/samples/damon/mtier.c
+++ b/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)
 {
@@ -182,6 +184,14 @@ static int damon_sample_mtier_enable_store(
 
 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;
 }