kobject: Make support for uevent_helper optional.

Support for uevent_helper, aka hotplug, is not required on many systems
these days but it can still be enabled via sysfs or sysctl.

Reported-by: Darren Shepherd <darren.s.shepherd@gmail.com>
Signed-off-by: Michael Marineau <mike@marineau.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

5 files changed, 25 insertions, 9 deletions

diff --git a/drivers/base/Kconfig b/drivers/base/Kconfig
index 8fa8deab6449..4b7b4522b64f 100644
--- a/drivers/base/Kconfig
+++ b/drivers/base/Kconfig
@@ -1,10 +1,10 @@
 menu "Generic Driver Options"
 
-config UEVENT_HELPER_PATH
-        string "path to uevent helper"
-        default ""
+config UEVENT_HELPER
+        bool "Support for uevent helper"
+        default y
         help
-          Path to uevent helper program forked by the kernel for
+          The uevent helper program is forked by the kernel for
           every uevent.
           Before the switch to the netlink-based uevent source, this was
           used to hook hotplug scripts into kernel device events. It
@@ -15,8 +15,13 @@ config UEVENT_HELPER_PATH
           that it creates a high system load, or on smaller systems
           it is known to create out-of-memory situations during bootup.
 
-          To disable user space helper program execution at early boot
-          time specify an empty string here. This setting can be altered
+config UEVENT_HELPER_PATH
+        string "path to uevent helper"
+        depends on UEVENT_HELPER
+        default ""
+        help
+          To disable user space helper program execution at by default
+          specify an empty string here. This setting can still be altered
           via /proc/sys/kernel/hotplug or via /sys/kernel/uevent_helper
           later at runtime.
 
diff --git a/include/linux/kobject.h b/include/linux/kobject.h
index f896a33e8341..2d61b909f414 100644
--- a/include/linux/kobject.h
+++ b/include/linux/kobject.h
@@ -32,8 +32,10 @@
 #define UEVENT_NUM_ENVP                 32      /* number of env pointers */
 #define UEVENT_BUFFER_SIZE              2048    /* buffer for the variables */
 
+#ifdef CONFIG_UEVENT_HELPER
 /* path to the userspace helper executed on an event */
 extern char uevent_helper[];
+#endif
 
 /* counter to tag the uevent, read only except for the kobject core */
 extern u64 uevent_seqnum;
diff --git a/kernel/ksysfs.c b/kernel/ksysfs.c
index 2495a9b14ac8..6683ccef9fff 100644
--- a/kernel/ksysfs.c
+++ b/kernel/ksysfs.c
@@ -37,6 +37,7 @@ static ssize_t uevent_seqnum_show(struct kobject *kobj,
 }
 KERNEL_ATTR_RO(uevent_seqnum);
 
+#ifdef CONFIG_UEVENT_HELPER
 /* uevent helper program, used during early boot */
 static ssize_t uevent_helper_show(struct kobject *kobj,
                                   struct kobj_attribute *attr, char *buf)
@@ -56,7 +57,7 @@ static ssize_t uevent_helper_store(struct kobject *kobj,
         return count;
 }
 KERNEL_ATTR_RW(uevent_helper);
-
+#endif
 
 #ifdef CONFIG_PROFILING
 static ssize_t profiling_show(struct kobject *kobj,
@@ -189,7 +190,9 @@ EXPORT_SYMBOL_GPL(kernel_kobj);
 static struct attribute * kernel_attrs[] = {
         &fscaps_attr.attr,
         &uevent_seqnum_attr.attr,
+#ifdef CONFIG_UEVENT_HELPER
         &uevent_helper_attr.attr,
+#endif
 #ifdef CONFIG_PROFILING
         &profiling_attr.attr,
 #endif
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 74f5b580fe34..bc966a8ffc3e 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -643,7 +643,7 @@ static struct ctl_table kern_table[] = {
                 .extra2         = &one,
         },
 #endif
-
+#ifdef CONFIG_UEVENT_HELPER
         {
                 .procname       = "hotplug",
                 .data           = &uevent_helper,
@@ -651,7 +651,7 @@ static struct ctl_table kern_table[] = {
                 .mode           = 0644,
                 .proc_handler   = proc_dostring,
         },
-
+#endif
 #ifdef CONFIG_CHR_DEV_SG
         {
                 .procname       = "sg-big-buff",
diff --git a/lib/kobject_uevent.c b/lib/kobject_uevent.c
index 4e3bd71bd949..9ebf9e20de53 100644
--- a/lib/kobject_uevent.c
+++ b/lib/kobject_uevent.c
@@ -29,7 +29,9 @@
 
 
 u64 uevent_seqnum;
+#ifdef CONFIG_UEVENT_HELPER
 char uevent_helper[UEVENT_HELPER_PATH_LEN] = CONFIG_UEVENT_HELPER_PATH;
+#endif
 #ifdef CONFIG_NET
 struct uevent_sock {
         struct list_head list;
@@ -109,6 +111,7 @@ static int kobj_bcast_filter(struct sock *dsk, struct sk_buff *skb, void *data)
 }
 #endif
 
+#ifdef CONFIG_UEVENT_HELPER
 static int kobj_usermode_filter(struct kobject *kobj)
 {
         const struct kobj_ns_type_operations *ops;
@@ -147,6 +150,7 @@ static void cleanup_uevent_env(struct subprocess_info *info)
 {
         kfree(info->data);
 }
+#endif
 
 /**
  * kobject_uevent_env - send an uevent with environmental data
@@ -323,6 +327,7 @@ int kobject_uevent_env(struct kobject *kobj, enum kobject_action action,
 #endif
         mutex_unlock(&uevent_sock_mutex);
 
+#ifdef CONFIG_UEVENT_HELPER
         /* call uevent_helper, usually only enabled during early boot */
         if (uevent_helper[0] && !kobj_usermode_filter(kobj)) {
                 struct subprocess_info *info;
@@ -347,6 +352,7 @@ int kobject_uevent_env(struct kobject *kobj, enum kobject_action action,
                         env = NULL;     /* freed by cleanup_uevent_env */
                 }
         }
+#endif
 
 exit:
         kfree(devpath);