Driver core: let request_module() send a /sys/modules/kmod/-uevent

On recent systems, calls to /sbin/modprobe are handled by udev depending
on the kind of device the kernel has discovered. This patch creates an
uevent for the kernels internal request_module(), to let udev take control
over the request, instead of forking the binary directly by the kernel.
The direct execution of /sbin/modprobe can be disabled by setting:
  /sys/module/kmod/mod_request_helper (/proc/sys/kernel/modprobe)
to an empty string, the same way /proc/sys/kernel/hotplug is disabled on an
udev system.
Signed-off-by: Kay Sievers <kay.sievers@vrfy.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

include/linux/kmod.h

@@ -28,8 +28,10 @@
 #ifdef CONFIG_KMOD
 /* modprobe exit status on success, -ve on error.  Return value
  * usually useless though. */
+extern void kmod_sysfs_init(void);
 extern int request_module(const char * name, ...) __attribute__ ((format (printf, 1, 2)));
 #else
+static inline void kmod_sysfs_init(void) {};
 static inline int request_module(const char * name, ...) { return -ENOSYS; }
 #endif
 

kernel/kmod.c

@@ -36,6 +36,8 @@
 #include <linux/resource.h>
 #include <asm/uaccess.h>
 
+extern int delete_module(const char *name, unsigned int flags);
+
 extern int max_threads;
 
 static struct workqueue_struct *khelper_wq;
@@ -46,6 +48,7 @@ static struct workqueue_struct *khelper_wq;
 	modprobe_path is set via /proc/sys.
 */
 char modprobe_path[KMOD_PATH_LEN] = "/sbin/modprobe";
+struct module_kobject kmod_mk;
 
 /**
  * request_module - try to load a kernel module
@@ -75,6 +78,11 @@ int request_module(const char *fmt, ...)
 	static atomic_t kmod_concurrent = ATOMIC_INIT(0);
 #define MAX_KMOD_CONCURRENT 50	/* Completely arbitrary value - KAO */
 	static int kmod_loop_msg;
+	char modalias[16 + MODULE_NAME_LEN] = "MODALIAS=";
+	char *uevent_envp[2] = {
+		modalias,
+		NULL
+	};
 
 	va_start(args, fmt);
 	ret = vsnprintf(module_name, MODULE_NAME_LEN, fmt, args);
@@ -82,6 +90,12 @@ int request_module(const char *fmt, ...)
 	if (ret >= MODULE_NAME_LEN)
 		return -ENAMETOOLONG;
 
+	strcpy(&modalias[strlen("MODALIAS=")], module_name);
+	kobject_uevent_env(&kmod_mk.kobj, KOBJ_CHANGE, uevent_envp);
+
+	if (modprobe_path[0] == '\0')
+		goto out;
+
 	/* If modprobe needs a service that is in a module, we get a recursive
 	 * loop.  Limit the number of running kmod threads to max_threads/2 or
 	 * MAX_KMOD_CONCURRENT, whichever is the smaller.  A cleaner method
@@ -108,9 +122,115 @@ int request_module(const char *fmt, ...)
 
 	ret = call_usermodehelper(modprobe_path, argv, envp, 1);
 	atomic_dec(&kmod_concurrent);
+out:
 	return ret;
 }
 EXPORT_SYMBOL(request_module);
+
+static ssize_t store_mod_request(struct module_attribute *mattr,
+				 struct module *mod,
+			      const char *buffer, size_t count)
+{
+	char name[MODULE_NAME_LEN];
+	int ret;
+
+	if (count < 1 || count+1 > MODULE_NAME_LEN)
+		return -EINVAL;
+	memcpy(name, buffer, count);
+	name[count] = '\0';
+	if (name[count-1] == '\n')
+		name[count-1] = '\0';
+
+	ret = request_module(name);
+	if (ret < 0)
+		return ret;
+	return count;
+}
+
+static struct module_attribute mod_request = {
+	.attr = { .name = "mod_request", .mode = S_IWUSR, .owner = THIS_MODULE },
+	.store = store_mod_request,
+};
+
+#ifdef CONFIG_MODULE_UNLOAD
+static ssize_t store_mod_unload(struct module_attribute *mattr,
+			    struct module *mod,
+			    const char *buffer, size_t count)
+{
+	char name[MODULE_NAME_LEN];
+	int ret;
+
+	if (count < 1 || count+1 > MODULE_NAME_LEN)
+		return -EINVAL;
+	memcpy(name, buffer, count);
+	name[count] = '\0';
+	if (name[count-1] == '\n')
+		name[count-1] = '\0';
+
+	ret = delete_module(name, O_NONBLOCK);
+	if (ret < 0)
+		return ret;
+	return count;
+}
+
+static struct module_attribute mod_unload = {
+	.attr = { .name = "mod_unload", .mode = S_IWUSR, .owner = THIS_MODULE },
+	.store = store_mod_unload,
+};
+#endif
+
+static ssize_t show_mod_request_helper(struct module_attribute *mattr,
+				       struct module *mod,
+				       char *buffer)
+{
+	return sprintf(buffer, "%s\n", modprobe_path);
+}
+
+static ssize_t store_mod_request_helper(struct module_attribute *mattr,
+					struct module *mod,
+					const char *buffer, size_t count)
+{
+	if (count < 1 || count+1 > KMOD_PATH_LEN)
+		return -EINVAL;
+	memcpy(modprobe_path, buffer, count);
+	modprobe_path[count] = '\0';
+	if (modprobe_path[count-1] == '\n')
+		modprobe_path[count-1] = '\0';
+	return count;
+}
+
+static struct module_attribute mod_request_helper = {
+	.attr = {
+		.name = "mod_request_helper",
+		.mode = S_IWUSR | S_IRUGO,
+		.owner = THIS_MODULE
+	},
+	.show = show_mod_request_helper,
+	.store = store_mod_request_helper,
+};
+
+void __init kmod_sysfs_init(void)
+{
+	int ret;
+
+	kmod_mk.mod = THIS_MODULE;
+	kobj_set_kset_s(&kmod_mk, module_subsys);
+	kobject_set_name(&kmod_mk.kobj, "kmod");
+	kobject_init(&kmod_mk.kobj);
+	ret = kobject_add(&kmod_mk.kobj);
+	if (ret < 0)
+		goto out;
+
+	ret = sysfs_create_file(&kmod_mk.kobj, &mod_request_helper.attr);
+	ret = sysfs_create_file(&kmod_mk.kobj, &mod_request.attr);
+#ifdef CONFIG_MODULE_UNLOAD
+	ret = sysfs_create_file(&kmod_mk.kobj, &mod_unload.attr);
+#endif
+
+	kobject_uevent(&kmod_mk.kobj, KOBJ_ADD);
+out:
+	return;
+}
 #endif /* CONFIG_KMOD */
 
 struct subprocess_info {

kernel/module.c

@@ -653,20 +653,11 @@ static void wait_for_zero_refcount(struct module *mod)
 	mutex_lock(&module_mutex);
 }
 
-asmlinkage long
-sys_delete_module(const char __user *name_user, unsigned int flags)
+int delete_module(const char *name, unsigned int flags)
 {
 	struct module *mod;
-	char name[MODULE_NAME_LEN];
 	int ret, forced = 0;
 
-	if (!capable(CAP_SYS_MODULE))
-		return -EPERM;
-
-	if (strncpy_from_user(name, name_user, MODULE_NAME_LEN-1) < 0)
-		return -EFAULT;
-	name[MODULE_NAME_LEN-1] = '\0';
-
 	if (mutex_lock_interruptible(&module_mutex) != 0)
 		return -EINTR;
 
@@ -727,6 +718,21 @@ sys_delete_module(const char __user *name_user, unsigned int flags)
 	return ret;
 }
 
+asmlinkage long
+sys_delete_module(const char __user *name_user, unsigned int flags)
+{
+	char name[MODULE_NAME_LEN];
+
+	if (!capable(CAP_SYS_MODULE))
+		return -EPERM;
+
+	if (strncpy_from_user(name, name_user, MODULE_NAME_LEN-1) < 0)
+		return -EFAULT;
+	name[MODULE_NAME_LEN-1] = '\0';
+
+	return delete_module(name, flags);
+}
+
 static void print_unload_info(struct seq_file *m, struct module *mod)
 {
 	struct module_use *use;

kernel/params.c

@@ -714,6 +714,7 @@ static int __init param_sysfs_init(void)
 	}
 
 	param_sysfs_builtin();
+	kmod_sysfs_init();
 
 	return 0;
 }