Thread (5 messages) 5 messages, 3 authors, 2023-10-12

Re: [PATCH v2] module: Add CONFIG_MODULE_LOAD_IN_SEQUENCE option

From: Luis Chamberlain <mcgrof@kernel.org>
Date: 2023-10-11 19:20:11
Also in: lkml

On Wed, Oct 11, 2023 at 01:14:38PM +0530, Joey Jiao wrote:
quoted hunk ↗ jump to hunk
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 <redacted>
---
 kernel/module/Kconfig | 11 +++++++++++
 kernel/module/main.c  |  3 ++-
 2 files changed, 13 insertions(+), 1 deletion(-)
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..e238a31d09eb 100644
--- a/kernel/module/main.c
+++ b/kernel/module/main.c
@@ -2594,7 +2594,8 @@ static noinline int do_init_module(struct module *mod)
 	 * rcu_barrier()
 	 */
 	if (llist_add(&freeinit->node, &init_free_list))
-		schedule_work(&init_free_wq);
+		if (!IS_ENABLED(CONFIG_MODULE_LOAD_IN_SEQUENCE)) {
+			schedule_work(&init_free_wq);
 
As Christoph suggested the rationale for something like this needs to be
clearly spelled out in the commit log and if so valuable it should be
a default. The commit log and even the Kconfig description do little
to justify any rationale for this.

  Luis
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