[PATCH] fix module sysfs files reference counting

The module files, refcnt, version, and srcversion did not properly
increment the owner's module reference count, allowing the modules to
be removed while the files were open, causing oopses.

This patch fixes this, and also fixes the problem that the version and
srcversion files were not showing up, unless CONFIG_MODULE_UNLOAD was
enabled, which is not correct.

Cc: Nathan Lynch <ntl@pobox.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

include/linux/module.h

@@ -245,6 +245,7 @@ struct module
 	/* Sysfs stuff. */
 	struct module_kobject mkobj;
 	struct module_param_attrs *param_attrs;
+	struct module_attribute *modinfo_attrs;
 	const char *version;
 	const char *srcversion;
 

kernel/module.c

@@ -429,7 +429,6 @@ static inline void percpu_modcopy(void *pcpudst, const void *src,
 }
 #endif /* CONFIG_SMP */
 
-#ifdef CONFIG_MODULE_UNLOAD
 #define MODINFO_ATTR(field)	\
 static void setup_modinfo_##field(struct module *mod, const char *s)  \
 {                                                                     \
@@ -461,12 +460,7 @@ static struct module_attribute modinfo_##field = {                    \
 MODINFO_ATTR(version);
 MODINFO_ATTR(srcversion);
 
-static struct module_attribute *modinfo_attrs[] = {
-	&modinfo_version,
-	&modinfo_srcversion,
-	NULL,
-};
-
+#ifdef CONFIG_MODULE_UNLOAD
 /* Init the unload section of the module. */
 static void module_unload_init(struct module *mod)
 {
@@ -781,6 +775,15 @@ static inline void module_unload_init(struct module *mod)
 }
 #endif /* CONFIG_MODULE_UNLOAD */
 
+static struct module_attribute *modinfo_attrs[] = {
+	&modinfo_version,
+	&modinfo_srcversion,
+#ifdef CONFIG_MODULE_UNLOAD
+	&refcnt,
+#endif
+	NULL,
+};
+
 #ifdef CONFIG_OBSOLETE_MODPARM
 /* Bounds checking done below */
 static int obsparm_copy_string(const char *val, struct kernel_param *kp)
@@ -1106,37 +1109,28 @@ static inline void remove_sect_attrs(struct module *mod)
 }
 #endif /* CONFIG_KALLSYMS */
 
-
-#ifdef CONFIG_MODULE_UNLOAD
-static inline int module_add_refcnt_attr(struct module *mod)
-{
-	return sysfs_create_file(&mod->mkobj.kobj, &refcnt.attr);
-}
-static void module_remove_refcnt_attr(struct module *mod)
-{
-	return sysfs_remove_file(&mod->mkobj.kobj, &refcnt.attr);
-}
-#else
-static inline int module_add_refcnt_attr(struct module *mod)
-{
-	return 0;
-}
-static void module_remove_refcnt_attr(struct module *mod)
-{
-}
-#endif
-
-#ifdef CONFIG_MODULE_UNLOAD
 static int module_add_modinfo_attrs(struct module *mod)
 {
 	struct module_attribute *attr;
+	struct module_attribute *temp_attr;
 	int error = 0;
 	int i;
 
+	mod->modinfo_attrs = kzalloc((sizeof(struct module_attribute) *
+					(ARRAY_SIZE(modinfo_attrs) + 1)),
+					GFP_KERNEL);
+	if (!mod->modinfo_attrs)
+		return -ENOMEM;
+
+	temp_attr = mod->modinfo_attrs;
 	for (i = 0; (attr = modinfo_attrs[i]) && !error; i++) {
 		if (!attr->test ||
-		    (attr->test && attr->test(mod)))
-			error = sysfs_create_file(&mod->mkobj.kobj,&attr->attr);
+		    (attr->test && attr->test(mod))) {
+			memcpy(temp_attr, attr, sizeof(*temp_attr));
+			temp_attr->attr.owner = mod;
+			error = sysfs_create_file(&mod->mkobj.kobj,&temp_attr->attr);
+			++temp_attr;
+		}
 	}
 	return error;
 }
@@ -1146,12 +1140,16 @@ static void module_remove_modinfo_attrs(struct module *mod)
 	struct module_attribute *attr;
 	int i;
 
-	for (i = 0; (attr = modinfo_attrs[i]); i++) {
+	for (i = 0; (attr = &mod->modinfo_attrs[i]); i++) {
+		/* pick a field to test for end of list */
+		if (!attr->attr.name)
+			break;
 		sysfs_remove_file(&mod->mkobj.kobj,&attr->attr);
-		attr->free(mod);
+		if (attr->free)
+			attr->free(mod);
 	}
+	kfree(mod->modinfo_attrs);
 }
-#endif
 
 static int mod_sysfs_setup(struct module *mod,
 			   struct kernel_param *kparam,
@@ -1169,19 +1167,13 @@ static int mod_sysfs_setup(struct module *mod,
 	if (err)
 		goto out;
 
-	err = module_add_refcnt_attr(mod);
-	if (err)
-		goto out_unreg;
-
 	err = module_param_sysfs_setup(mod, kparam, num_params);
 	if (err)
 		goto out_unreg;
 
-#ifdef CONFIG_MODULE_UNLOAD
 	err = module_add_modinfo_attrs(mod);
 	if (err)
 		goto out_unreg;
-#endif
 
 	return 0;
 
@@ -1193,10 +1185,7 @@ out:
 
 static void mod_kobject_remove(struct module *mod)
 {
-#ifdef CONFIG_MODULE_UNLOAD
 	module_remove_modinfo_attrs(mod);
-#endif
-	module_remove_refcnt_attr(mod);
 	module_param_sysfs_remove(mod);
 
 	kobject_unregister(&mod->mkobj.kobj);
@@ -1474,7 +1463,6 @@ static char *get_modinfo(Elf_Shdr *sechdrs,
 	return NULL;
 }
 
-#ifdef CONFIG_MODULE_UNLOAD
 static void setup_modinfo(struct module *mod, Elf_Shdr *sechdrs,
 			  unsigned int infoindex)
 {
@@ -1489,7 +1477,6 @@ static void setup_modinfo(struct module *mod, Elf_Shdr *sechdrs,
 						attr->attr.name));
 	}
 }
-#endif
 
 #ifdef CONFIG_KALLSYMS
 int is_exported(const char *name, const struct module *mod)
@@ -1803,10 +1790,8 @@ static struct module *load_module(void __user *umod,
 	if (strcmp(mod->name, "driverloader") == 0)
 		add_taint(TAINT_PROPRIETARY_MODULE);
 
-#ifdef CONFIG_MODULE_UNLOAD
 	/* Set up MODINFO_ATTR fields */
 	setup_modinfo(mod, sechdrs, infoindex);
-#endif
 
 	/* Fix up syms, so that st_value is a pointer to location. */
 	err = simplify_symbols(sechdrs, symindex, strtab, versindex, pcpuindex,

kernel/params.c

@@ -638,13 +638,8 @@ static ssize_t module_attr_show(struct kobject *kobj,
 	if (!attribute->show)
 		return -EIO;
 
-	if (!try_module_get(mk->mod))
-		return -ENODEV;
-
 	ret = attribute->show(attribute, mk->mod, buf);
 
-	module_put(mk->mod);
-
 	return ret;
 }
 
@@ -662,13 +657,8 @@ static ssize_t module_attr_store(struct kobject *kobj,
 	if (!attribute->store)
 		return -EIO;
 
-	if (!try_module_get(mk->mod))
-		return -ENODEV;
-
 	ret = attribute->store(attribute, mk->mod, buf, len);
 
-	module_put(mk->mod);
-
 	return ret;
 }