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>

1 files changed, 120 insertions, 0 deletions

diff --git a/kernel/kmod.c b/kernel/kmod.c
index 796276141e51..9f923f8ce6a0 100644
--- a/kernel/kmod.c
+++ b/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 {