param: fix module param locks when !CONFIG_SYSFS.

As Dan Streetman points out, the entire point of locking for is to
stop sysfs accesses, so they're elided entirely in the !SYSFS case.

Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

3 files changed, 24 insertions, 5 deletions

diff --git a/include/linux/module.h b/include/linux/module.h
index 6ba0e87fa804..46efa1c9de60 100644
--- a/include/linux/module.h
+++ b/include/linux/module.h
@@ -240,7 +240,9 @@ struct module {
         unsigned int num_syms;
 
         /* Kernel parameters. */
+#ifdef CONFIG_SYSFS
         struct mutex param_lock;
+#endif
         struct kernel_param *kp;
         unsigned int num_kp;
 
diff --git a/kernel/module.c b/kernel/module.c
index 8ec33ce202a6..b4994adf7187 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -1820,6 +1820,10 @@ static void mod_sysfs_fini(struct module *mod)
         mod_kobject_put(mod);
 }
 
+static void init_param_lock(struct module *mod)
+{
+        mutex_init(&mod->param_lock);
+}
 #else /* !CONFIG_SYSFS */
 
 static int mod_sysfs_setup(struct module *mod,
@@ -1842,6 +1846,9 @@ static void del_usage_links(struct module *mod)
 {
 }
 
+static void init_param_lock(struct module *mod)
+{
+}
 #endif /* CONFIG_SYSFS */
 
 static void mod_sysfs_teardown(struct module *mod)
@@ -3442,7 +3449,7 @@ static int load_module(struct load_info *info, const char __user *uargs,
         if (err)
                 goto unlink_mod;
 
-        mutex_init(&mod->param_lock);
+        init_param_lock(mod);
 
         /* Now we've got everything in the final locations, we can
          * find optional sections. */
diff --git a/kernel/params.c b/kernel/params.c
index 8890d0b8dffc..faa461c16f12 100644
--- a/kernel/params.c
+++ b/kernel/params.c
@@ -25,12 +25,22 @@
 #include <linux/slab.h>
 #include <linux/ctype.h>
 
+#ifdef CONFIG_SYSFS
 /* Protects all built-in parameters, modules use their own param_lock */
 static DEFINE_MUTEX(param_lock);
 
 /* Use the module's mutex, or if built-in use the built-in mutex */
 #define KPARAM_MUTEX(mod)       ((mod) ? &(mod)->param_lock : &param_lock)
-#define KPARAM_IS_LOCKED(mod)   mutex_is_locked(KPARAM_MUTEX(mod))
+
+static inline void check_kparam_locked(struct module *mod)
+{
+        BUG_ON(!mutex_is_locked(KPARAM_MUTEX(mod)));
+}
+#else
+static inline void check_kparam_locked(struct module *mod)
+{
+}
+#endif /* !CONFIG_SYSFS */
 
 /* This just allows us to keep track of which parameters are kmalloced. */
 struct kmalloced_param {
@@ -459,7 +469,7 @@ static int param_array(struct module *mod,
                 /* nul-terminate and parse */
                 save = val[len];
                 ((char *)val)[len] = '\0';
-                BUG_ON(!KPARAM_IS_LOCKED(mod));
+                check_kparam_locked(mod);
                 ret = set(val, &kp);
 
                 if (ret != 0)
@@ -496,7 +506,7 @@ static int param_array_get(char *buffer, const struct kernel_param *kp)
                 if (i)
                         buffer[off++] = ',';
                 p.arg = arr->elem + arr->elemsize * i;
-                BUG_ON(!KPARAM_IS_LOCKED(p.mod));
+                check_kparam_locked(p.mod);
                 ret = arr->ops->get(buffer + off, &p);
                 if (ret < 0)
                         return ret;
@@ -616,6 +626,7 @@ static ssize_t param_attr_store(struct module_attribute *mattr,
 #define __modinit __init
 #endif
 
+#ifdef CONFIG_SYSFS
 void kernel_param_lock(struct module *mod)
 {
         mutex_lock(KPARAM_MUTEX(mod));
@@ -626,7 +637,6 @@ void kernel_param_unlock(struct module *mod)
         mutex_unlock(KPARAM_MUTEX(mod));
 }
 
-#ifdef CONFIG_SYSFS
 EXPORT_SYMBOL(kernel_param_lock);
 EXPORT_SYMBOL(kernel_param_unlock);