module: Fix freeing of charp module parameters when CONFIG_SYSFS=n

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>
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>

1 files changed, 3 insertions, 8 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