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From:   Joey Jiao <quic_jiangenj@quicinc.com>
To:     <linux-modules@vger.kernel.org>
CC:     <quic_jiangenj@quicinc.com>, Luis Chamberlain <mcgrof@kernel.org>,
        <linux-kernel@vger.kernel.org>
Subject: [PATCH] module: Add CONFIG_MODULE_LOAD_IN_SEQUENCE option
Date:   Mon, 9 Oct 2023 10:26:35 +0530
Message-ID: <20231009045636.4143-1-quic_jiangenj@quicinc.com>
MIME-Version: 1.0
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Precedence: bulk

When modprobe cmds are executed one by one, the final loaded modules
are not in fixed sequence as expected.

Add the option to make sure modules are in fixed sequence across reboot.

Signed-off-by: Joey Jiao <quic_jiangenj@quicinc.com>
---
 kernel/module/Kconfig | 11 +++++++++++
 kernel/module/main.c  |  6 ++++++
 2 files changed, 17 insertions(+)

diff --git a/kernel/module/Kconfig b/kernel/module/Kconfig
index 33a2e991f608..b45a45f31d6d 100644
--- a/kernel/module/Kconfig
+++ b/kernel/module/Kconfig
@@ -389,4 +389,15 @@ config MODULES_TREE_LOOKUP
 	def_bool y
 	depends on PERF_EVENTS || TRACING || CFI_CLANG
 
+config MODULE_LOAD_IN_SEQUENCE
+	bool "Load module in sequence"
+	default n
+	help
+	  By default, modules are loaded in random sequence depending on when modprobe
+	  is executed.
+
+	  This option allows modules to be loaded in sequence if modprobe cmds are
+	  executed one by one in sequence. This option is helpful during syzkaller fuzzing
+	  to make sure module is loaded into fixed address across device reboot.
+
 endif # MODULES
diff --git a/kernel/module/main.c b/kernel/module/main.c
index 98fedfdb8db5..587fd84083ae 100644
--- a/kernel/module/main.c
+++ b/kernel/module/main.c
@@ -2593,11 +2593,17 @@ static noinline int do_init_module(struct module *mod)
 	 * be cleaned up needs to sync with the queued work - ie
 	 * rcu_barrier()
 	 */
+#ifdef CONFIG_MODULE_LOAD_IN_SEQUENCE
+	llist_add(&freeinit->node, &init_free_list);
+#else
 	if (llist_add(&freeinit->node, &init_free_list))
 		schedule_work(&init_free_wq);
+#endif
 
 	mutex_unlock(&module_mutex);
+#ifdef CONFIG_MODULE_LOAD_IN_SEQUENCE
 	wake_up_all(&module_wq);
+#endif
 
 	mod_stat_add_long(text_size, &total_text_size);
 	mod_stat_add_long(total_size, &total_mod_size);
-- 
2.42.0