linux-kernel - [PATCH 5/6] module: store and complete idempotent upon force unloading

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Message-ID: <20250918201109.24620-12-julian.lagattuta@gmail.com>
Date: Thu, 18 Sep 2025 16:11:14 -0400
From: julian-lagattuta <julian.lagattuta@...il.com>
To: Luis Chamberlain <mcgrof@...nel.org>,
	Petr Pavlu <petr.pavlu@...e.com>
Cc: Sami Tolvanen <samitolvanen@...gle.com>,
	Daniel Gomez <da.gomez@...sung.com>,
	linux-modules@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	julian-lagattuta <julian.lagattuta@...il.com>
Subject: [PATCH 5/6] module: store and complete idempotent upon force unloading

Move idempotent definition up and add idempotent_complete declaration.

Add idempotent to struct load_info which gets passed into load_module
and then stored in the struct module.

run idempotent_complete after module is unloaded and give EBUSY
to any process waiting for the module to finish initializing
via finit_module.

Signed-off-by: julian-lagattuta <julian.lagattuta@...il.com>
---
 kernel/module/internal.h |  3 +++
 kernel/module/main.c     | 29 +++++++++++++++++++++--------
 2 files changed, 24 insertions(+), 8 deletions(-)

diff --git a/kernel/module/internal.h b/kernel/module/internal.h
index 8d74b0a21c82..43f537475859 100644
--- a/kernel/module/internal.h
+++ b/kernel/module/internal.h
@@ -89,6 +89,9 @@ struct load_info {
 		unsigned int vers_ext_crc;
 		unsigned int vers_ext_name;
 	} index;
+#ifdef CONFIG_MODULE_FORCE_UNLOAD
+	struct idempotent* idempotent;
+#endif
 };
 
 enum mod_license {
diff --git a/kernel/module/main.c b/kernel/module/main.c
index 217185dbc3c1..256e30259bcf 100644
--- a/kernel/module/main.c
+++ b/kernel/module/main.c
@@ -80,6 +80,17 @@ static void do_free_init(struct work_struct *w);
 static DECLARE_WORK(init_free_wq, do_free_init);
 static LLIST_HEAD(init_free_list);
 
+
+struct idempotent {
+	const void *cookie;
+	struct hlist_node entry;
+	struct completion complete;
+	int ret;
+};
+
+static int idempotent_complete(struct idempotent *u, int ret);
+
+
 struct mod_tree_root mod_tree __cacheline_aligned = {
 	.addr_min = -1UL,
 };
@@ -784,7 +795,7 @@ SYSCALL_DEFINE2(delete_module, const char __user *, name_user,
 		!IS_ENABLED(CONFIG_MODULE_FORCE_UNLOAD))
 	) {
 		if (mod->state == MODULE_STATE_GOING)
-		pr_debug("%s already dying\n", mod->name);
+			pr_debug("%s already dying\n", mod->name);
 		ret = -EBUSY;
 		goto out;
 	}
@@ -833,6 +844,11 @@ SYSCALL_DEFINE2(delete_module, const char __user *, name_user,
 	strscpy(last_unloaded_module.name, mod->name);
 	strscpy(last_unloaded_module.taints, module_flags(mod, buf, false));
 
+#ifdef CONFIG_MODULE_FORCE_UNLOAD
+	if (did_init_crash && mod->idempotent)
+		idempotent_complete(mod->idempotent, -EBUSY);
+#endif
+
 	free_module(mod);
 	/* someone could wait for the module in add_unformed_module() */
 	wake_up_all(&module_wq);
@@ -3591,12 +3607,6 @@ SYSCALL_DEFINE3(init_module, void __user *, umod,
 	return load_module(&info, uargs, 0);
 }
 
-struct idempotent {
-	const void *cookie;
-	struct hlist_node entry;
-	struct completion complete;
-	int ret;
-};
 
 #define IDEM_HASH_BITS 8
 static struct hlist_head idem_hash[1 << IDEM_HASH_BITS];
@@ -3683,7 +3693,7 @@ static int idempotent_wait_for_completion(struct idempotent *u)
 	return ret;
 }
 
-static int init_module_from_file(struct file *f, const char __user * uargs, int flags)
+static int init_module_from_file(struct file *f, const char __user * uargs, int flags, struct idempotent *idempotent __maybe_unused)
 {
 	struct load_info info = { };
 	void *buf = NULL;
@@ -3707,6 +3717,9 @@ static int init_module_from_file(struct file *f, const char __user * uargs, int
 		info.hdr = buf;
 		info.len = len;
 	}
+#ifdef CONFIG_MODULE_FORCE_UNLOAD
+	info.idempotent = idempotent;
+#endif
 
 	return load_module(&info, uargs, flags);
 }
-- 
2.45.2