[PATCH v2 1/3] module: Fix freeing of charp module parameters when CONFIG_SYSFS=n

[Petr Pavlu <petr.pavlu@suse.com>]

When setting a charp module parameter, the param_set_charp() function
allocates memory to store a copy of the input value. Later, when the module
is potentially unloaded, the destroy_params() function is called to free
this allocated memory.

However, destroy_params() is available only when CONFIG_SYSFS=y, otherwise
only a dummy variant is present. In the unlikely case that the kernel is
configured with CONFIG_MODULES=y and CONFIG_SYSFS=n, this results in
a memory leak of charp values when a module is unloaded.

Fix this issue by making destroy_params() always available when
CONFIG_MODULES=y. Rename the function to module_destroy_params() to clarify
that it is intended for use by the module loader.

Fixes: e180a6b7759a ("param: fix charp parameters set via sysfs")
Signed-off-by: Petr Pavlu <petr.pavlu@suse.com>
---
 include/linux/moduleparam.h | 11 +++--------
 kernel/module/main.c        |  4 ++--
 kernel/params.c             | 27 ++++++++++++++++++---------
 3 files changed, 23 insertions(+), 19 deletions(-)

diff --git a/include/linux/moduleparam.h b/include/linux/moduleparam.h
index 7d22d4c4ea2e..8667f72503d9 100644
--- a/include/linux/moduleparam.h
+++ b/include/linux/moduleparam.h
@@ -426,14 +426,9 @@ extern char *parse_args(const char *name,
 		      void *arg, parse_unknown_fn unknown);
 
 /* Called by module remove. */
-#ifdef CONFIG_SYSFS
-extern void destroy_params(const struct kernel_param *params, unsigned num);
-#else
-static inline void destroy_params(const struct kernel_param *params,
-				  unsigned num)
-{
-}
-#endif /* !CONFIG_SYSFS */
+#ifdef CONFIG_MODULES
+void module_destroy_params(const struct kernel_param *params, unsigned int num);
+#endif
 
 /* All the helper functions */
 /* The macros to do compile-time type checking stolen from Jakub
diff --git a/kernel/module/main.c b/kernel/module/main.c
index c3ce106c70af..ef2e2130972f 100644
--- a/kernel/module/main.c
+++ b/kernel/module/main.c
@@ -1408,7 +1408,7 @@ static void free_module(struct module *mod)
 	module_unload_free(mod);
 
 	/* Free any allocated parameters. */
-	destroy_params(mod->kp, mod->num_kp);
+	module_destroy_params(mod->kp, mod->num_kp);
 
 	if (is_livepatch_module(mod))
 		free_module_elf(mod);
@@ -3519,7 +3519,7 @@ static int load_module(struct load_info *info, const char __user *uargs,
 	mod_sysfs_teardown(mod);
  coming_cleanup:
 	mod->state = MODULE_STATE_GOING;
-	destroy_params(mod->kp, mod->num_kp);
+	module_destroy_params(mod->kp, mod->num_kp);
 	blocking_notifier_call_chain(&module_notify_list,
 				     MODULE_STATE_GOING, mod);
 	klp_module_going(mod);
diff --git a/kernel/params.c b/kernel/params.c
index 7188a12dbe86..c6a354d54213 100644
--- a/kernel/params.c
+++ b/kernel/params.c
@@ -745,15 +745,6 @@ void module_param_sysfs_remove(struct module *mod)
 }
 #endif
 
-void destroy_params(const struct kernel_param *params, unsigned num)
-{
-	unsigned int i;
-
-	for (i = 0; i < num; i++)
-		if (params[i].ops->free)
-			params[i].ops->free(params[i].arg);
-}
-
 struct module_kobject * __init_or_module
 lookup_or_create_module_kobject(const char *name)
 {
@@ -985,3 +976,21 @@ static int __init param_sysfs_builtin_init(void)
 late_initcall(param_sysfs_builtin_init);
 
 #endif /* CONFIG_SYSFS */
+
+#ifdef CONFIG_MODULES
+
+/*
+ * module_destroy_params - free all parameters for one module
+ * @params: module parameters (array)
+ * @num: number of module parameters
+ */
+void module_destroy_params(const struct kernel_param *params, unsigned int num)
+{
+	unsigned int i;
+
+	for (i = 0; i < num; i++)
+		if (params[i].ops->free)
+			params[i].ops->free(params[i].arg);
+}
+
+#endif /* CONFIG_MODULES */
-- 
2.53.0