Merge tag 'trace-v7.3-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-tracegrafted

Pull tracing fixes from Steven Rostedt:

 - Don't destroy user event fields when removal fails

   User event fields are destroyed before the event is removed from
   visibility. But that can fail leaving the still visible event with no
   fields. Move the destroying of the fields to after the event is
   successfully removed from visibility.

 - Initialize function graph state is fork before calling
   copy_exec_state()

   For non-CLONE_VM forks, copy_exec_state() allocates a new
   task_exec_state. If that allocation fails, ftrace_graph_exit_task()
   will free the tasks ret_stack pointer. Since that pointer is still
   using the parent's ret_stack, it mistakenly frees the parent's
   pointer too.

   Call ftrace_graph_init() on the task first which will NULL out the
   new tasks's ret_stack and if the copy fails, it will not free
   anything.

 - Remove FGRAPH_MAX_INDEX

   The macro FGRAPH_MAX_INDEX was added but never used. Remove it.

 - Save ent_size in function graph printing of nested functions

   The function graph tracer needs to look at the next event to see if
   the next event is the return of the current function entry. If it is,
   it prints a single line:

	ktime_get();

   Otherwise it prints it like a nested function:

	tick_nohz_irq_exit() {
	    ktime_get();
	    kcpustat_irq_exit();
	}

   In order to look at the next event, it must save the current event so
   that it has the information to print from it. It saves the event in
   the iterator descriptor called "ent". What it doesn't save is the
   ent_size of the event which is now used to know if the function graph
   arguments are to be printed. The peek doesn't save the size so the
   size used happens to be that of the size of the last event that was
   seen.

   Save the entry event size in the iterator descriptor so that the
   correct size is used.

 - Fix several errors with freeing data in the histogram code

   The histogram code had a lot of leaked or or incorrect accounting
   when failures happen. Correct them.

 - Fix histogram regression of .percent and .graph modifiers

   Up until 6.3 histogram values could have "percent" or "graph"
   modifiers that changed how they were printed. But a change that added
   restricting histograms values from being strings, stack traces and
   other modifiers inadvertently prevented them from using the percent
   and graph modifiers, which were legal use cases for values.

   Put back the percent and graph modifiers.

 - Fix various typos in the comments

 - Set the trace_clock before initializing a histogram with clock
   argument

   The histogram API allows the user to specific which trace clock to
   use via a "clock=" string. The histogram is set up first before the
   clock is checked. If the passed in clock is not valid, it exits
   without fully fixing up the histogram leaving it on the list and a
   use-after-free can trigger.

   Update the clock argument first and if it fails then exit gracefully
   before the histogram trigger is placed on any lists.

 - Restore :mod: trailer after parsing in ftrace_set_clr_event

   The function ftrace_set_clr_event() modifies the parse string and
   needs to put it back to what was passed in. It searches for ":mod:"
   via a strsep() but fails to put back the first ':' in the string.

   Add back the ':' in the passed in string.

 - Take trace_array reference when opening a tracer options file

   The options files are dynamically created and some tracers add their
   own options. When a tracer adds their own list of options, the
   trace_array holding them has an array to hold the list of options for
   each tracer. This array increases in size via a krealloc(), and the
   new entry gets a newly allocated array to hold the options of the new
   tracer being added.

   The element in each entry of the tracer's option array holds a
   pointer back to the trace_array, a pointer to the tracer it is
   associated to, a pointer to the flags of the option.

   The issue is that these arrays are freed when the trace_array is
   freed when its instance it represents is removed from the instances
   directory. There's a race that an open of one of these options files
   can happen when the instance is being removed.

   Add a new helper function to be called by the open function of the
   options file to iterate all existing trace_arrays under a lock and
   find the one that has the given option element in one of it's tracer
   arrays. If found, then update the associated trace_array's reference
   counter to keep it from being freed. If not found, have the open call
   return -ENODEV.

 - Disable interrupts when acquiring the lock in rb_wake_up_waiters()

   The function rb_wake_up_waiters() assumes it will be called in
   interrupt context and does not disable irqs when taking
   cpu_buffer->reader_lock, which can be called in hard interrupt
   context. The issue is in PREEMPT_RT, this function is called in
   thread context leaving this lock open to a deadlock.

   Take the lock with interrupts disabled.

 - Use rcu_assign_pointer() for tmp_ops filter hash

   The tmp_ops used in update_ftrace_direct_mod() assigns its
   filter_hash field directly, but that field is annotated as __rcu and
   sparse complains. Assign it with rcu_assign_pointer()

 - Fix use-after-free in enable_trigger_private_data_free()

   The trace_event_call is accessed through the event_trigger_data's
   trace_event_file pointer to put the trace_event_call on freeing. The
   issue is that the trace_event_file data may have been freed already
   causing a use-after-free. Add a field to the event_trigger_data that
   points directly to the trace_event_call so that it can decrement its
   reference directly without needing to go through the
   trace_event_file.

 - Fix accounting of buffer data remote headers

   trace_buffer_desc_size() and trace_remote_alloc_buffer() undercount
   the number of pages is needed for the asked for size as it doesn't
   take into account the meta data on each page. Add a helper function
   to do the calculation properly and use that in these functions.

 - Catch nr_page_va overflow in ring_buffer_desc sizing

   The number of pages per remote ring buffer is capped by
   ring_buffer_desc::nr_page_va (32 bits). A buffer_size large enough to
   overflow that field would silently allocate a descriptor smaller than
   what was asked for.

 - Do not resize the subbuf order if any per_cpu buffer is disabled

   The mmapping of ring buffers disables resizing the subbuffers, but it
   is done per-cpu whereas the subbuf size change is done for all the
   per_cpu buffers under the buffer->mutex. It could change the size of
   some while the mapping is happening on others. Have the resize of the
   subbuf order check all the per_cpu buffers under the lock to see if
   any of them is disabled before starting and causing an inconsistency
   between buffers that are being mapped.

* tag 'trace-v7.3-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace: (25 commits)
  ring-buffer: Check resize_disabled before publishing the new subbuf order
  tracing/remotes: Catch nr_page_va overflow in ring_buffer_desc sizing
  tracing/remotes: Account for ring buffer page header in size calculation
  tracing: Don't dereference trace_event_file in deferred trigger free
  ftrace: Use rcu_assign_pointer() for tmp_ops filter hash
  ring-buffer: Acquire the lock with irqsave in rb_wake_up_waiters()
  tracing: Take trace_array reference when opening a tracer options file
  tracing: Fix ring_buffer_read_page_size() kernel-doc
  tracing: Restore :mod: trailer after parsing in ftrace_set_clr_event()
  tracing: Fix memory corruption from a "STACKTRACE" histogram key
  tracing: Fix memory corruption from the histogram stacktrace modifier
  tracing: Undo the registration when enabling the histogram trigger fails
  tracing: Take the reference before publishing the named histogram trigger
  tracing: Set the trace clock before registering the histogram trigger
  tracing: Fix typo "preceeded" in comment
  tracing: Fix typo "availabe" in comment
  tracing: Let histogram values keep the percent and graph modifiers
  tracing: Keep the entry count when the histogram stats allocation fails
  tracing: Free histogram the field rejected for a bad modifier
  tracing: Free histogram the var ref when its initialization fails
  ...

1 files changed, 851 insertions, 0 deletions

diff --git a/lib/kobject_uevent.c b/lib/kobject_uevent.c
new file mode 100644
index 000000000..ddbc4d748
--- /dev/null
+++ b/lib/kobject_uevent.c
@@ -0,0 +1,851 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * kernel userspace event delivery
+ *
+ * Copyright (C) 2004 Red Hat, Inc.  All rights reserved.
+ * Copyright (C) 2004 Novell, Inc.  All rights reserved.
+ * Copyright (C) 2004 IBM, Inc. All rights reserved.
+ *
+ * Authors:
+ *	Robert Love		<rml@novell.com>
+ *	Kay Sievers		<kay.sievers@vrfy.org>
+ *	Arjan van de Ven	<arjanv@redhat.com>
+ *	Greg Kroah-Hartman	<greg@kroah.com>
+ */
+
+#include <linux/spinlock.h>
+#include <linux/string.h>
+#include <linux/kobject.h>
+#include <linux/export.h>
+#include <linux/kmod.h>
+#include <linux/slab.h>
+#include <linux/socket.h>
+#include <linux/skbuff.h>
+#include <linux/netlink.h>
+#include <linux/uidgid.h>
+#include <linux/uuid.h>
+#include <linux/ctype.h>
+#include <net/sock.h>
+#include <net/netlink.h>
+#include <net/net_namespace.h>
+
+
+atomic64_t uevent_seqnum;
+#ifdef CONFIG_UEVENT_HELPER
+char uevent_helper[UEVENT_HELPER_PATH_LEN] = CONFIG_UEVENT_HELPER_PATH;
+#endif
+
+struct uevent_sock {
+	struct list_head list;
+	struct sock *sk;
+};
+
+#ifdef CONFIG_NET
+static LIST_HEAD(uevent_sock_list);
+/* This lock protects uevent_sock_list */
+static DEFINE_MUTEX(uevent_sock_mutex);
+#endif
+
+/* the strings here must match the enum in include/linux/kobject.h */
+static const char *kobject_actions[] = {
+	[KOBJ_ADD] =		"add",
+	[KOBJ_REMOVE] =		"remove",
+	[KOBJ_CHANGE] =		"change",
+	[KOBJ_MOVE] =		"move",
+	[KOBJ_ONLINE] =		"online",
+	[KOBJ_OFFLINE] =	"offline",
+	[KOBJ_BIND] =		"bind",
+	[KOBJ_UNBIND] =		"unbind",
+};
+
+static int kobject_action_type(const char *buf, size_t count,
+			       enum kobject_action *type,
+			       const char **args)
+{
+	enum kobject_action action;
+	size_t count_first;
+	const char *args_start;
+	int ret = -EINVAL;
+
+	if (count && (buf[count-1] == '\n' || buf[count-1] == '\0'))
+		count--;
+
+	if (!count)
+		goto out;
+
+	args_start = strnchr(buf, count, ' ');
+	if (args_start) {
+		count_first = args_start - buf;
+		args_start = args_start + 1;
+	} else
+		count_first = count;
+
+	for (action = 0; action < ARRAY_SIZE(kobject_actions); action++) {
+		if (strncmp(kobject_actions[action], buf, count_first) != 0)
+			continue;
+		if (kobject_actions[action][count_first] != '\0')
+			continue;
+		if (args)
+			*args = args_start;
+		*type = action;
+		ret = 0;
+		break;
+	}
+out:
+	return ret;
+}
+
+static const char *action_arg_word_end(const char *buf, const char *buf_end,
+				       char delim)
+{
+	const char *next = buf;
+
+	while (next <= buf_end && *next != delim)
+		if (!isalnum(*next++))
+			return NULL;
+
+	if (next == buf)
+		return NULL;
+
+	return next;
+}
+
+static int kobject_action_args(const char *buf, size_t count,
+			       struct kobj_uevent_env **ret_env)
+{
+	struct kobj_uevent_env *env = NULL;
+	const char *next, *buf_end, *key;
+	int key_len;
+	int r = -EINVAL;
+
+	if (count && (buf[count - 1] == '\n' || buf[count - 1] == '\0'))
+		count--;
+
+	if (!count)
+		return -EINVAL;
+
+	env = kzalloc_obj(*env);
+	if (!env)
+		return -ENOMEM;
+
+	/* first arg is UUID */
+	if (count < UUID_STRING_LEN || !uuid_is_valid(buf) ||
+	    add_uevent_var(env, "SYNTH_UUID=%.*s", UUID_STRING_LEN, buf))
+		goto out;
+
+	/*
+	 * the rest are custom environment variables in KEY=VALUE
+	 * format with ' ' delimiter between each KEY=VALUE pair
+	 */
+	next = buf + UUID_STRING_LEN;
+	buf_end = buf + count - 1;
+
+	while (next <= buf_end) {
+		if (*next != ' ')
+			goto out;
+
+		/* skip the ' ', key must follow */
+		key = ++next;
+		if (key > buf_end)
+			goto out;
+
+		buf = next;
+		next = action_arg_word_end(buf, buf_end, '=');
+		if (!next || next > buf_end || *next != '=')
+			goto out;
+		key_len = next - buf;
+
+		/* skip the '=', value must follow */
+		if (++next > buf_end)
+			goto out;
+
+		buf = next;
+		next = action_arg_word_end(buf, buf_end, ' ');
+		if (!next)
+			goto out;
+
+		if (add_uevent_var(env, "SYNTH_ARG_%.*s=%.*s",
+				   key_len, key, (int) (next - buf), buf))
+			goto out;
+	}
+
+	r = 0;
+out:
+	if (r)
+		kfree(env);
+	else
+		*ret_env = env;
+	return r;
+}
+
+/**
+ * kobject_synth_uevent - send synthetic uevent with arguments
+ *
+ * @kobj: struct kobject for which synthetic uevent is to be generated
+ * @buf: buffer containing action type and action args, newline is ignored
+ * @count: length of buffer
+ *
+ * Returns 0 if kobject_synthetic_uevent() is completed with success or the
+ * corresponding error when it fails.
+ */
+int kobject_synth_uevent(struct kobject *kobj, const char *buf, size_t count)
+{
+	char *no_uuid_envp[] = { "SYNTH_UUID=0", NULL };
+	enum kobject_action action;
+	const char *action_args;
+	struct kobj_uevent_env *env;
+	const char *msg = NULL, *devpath;
+	int r;
+
+	r = kobject_action_type(buf, count, &action, &action_args);
+	if (r) {
+		msg = "unknown uevent action string";
+		goto out;
+	}
+
+	if (!action_args) {
+		r = kobject_uevent_env(kobj, action, no_uuid_envp);
+		goto out;
+	}
+
+	r = kobject_action_args(action_args,
+				count - (action_args - buf), &env);
+	if (r == -EINVAL) {
+		msg = "incorrect uevent action arguments";
+		goto out;
+	}
+
+	if (r)
+		goto out;
+
+	r = kobject_uevent_env(kobj, action, env->envp);
+	kfree(env);
+out:
+	if (r) {
+		devpath = kobject_get_path(kobj, GFP_KERNEL);
+		pr_warn("synth uevent: %s: %s\n",
+		       devpath ?: "unknown device",
+		       msg ?: "failed to send uevent");
+		kfree(devpath);
+	}
+	return r;
+}
+
+#ifdef CONFIG_UEVENT_HELPER
+static int kobj_usermode_filter(struct kobject *kobj)
+{
+	const struct kobj_ns_type_operations *ops;
+
+	ops = kobj_ns_ops(kobj);
+	if (ops) {
+		const struct ns_common *init_ns, *ns;
+
+		ns = kobj->ktype->namespace(kobj);
+		init_ns = ops->initial_ns();
+		return ns != init_ns;
+	}
+
+	return 0;
+}
+
+static int init_uevent_argv(struct kobj_uevent_env *env, const char *subsystem)
+{
+	int buffer_size = sizeof(env->buf) - env->buflen;
+	int len;
+
+	len = strscpy(&env->buf[env->buflen], subsystem, buffer_size);
+	if (len < 0) {
+		pr_warn("%s: insufficient buffer space (%u left) for %s\n",
+			__func__, buffer_size, subsystem);
+		return -ENOMEM;
+	}
+
+	env->argv[0] = uevent_helper;
+	env->argv[1] = &env->buf[env->buflen];
+	env->argv[2] = NULL;
+
+	env->buflen += len + 1;
+	return 0;
+}
+
+static void cleanup_uevent_env(struct subprocess_info *info)
+{
+	kfree(info->data);
+}
+#endif
+
+#ifdef CONFIG_NET
+static struct sk_buff *alloc_uevent_skb(struct kobj_uevent_env *env,
+					const char *action_string,
+					const char *devpath)
+{
+	struct netlink_skb_parms *parms;
+	struct sk_buff *skb = NULL;
+	char *scratch;
+	size_t len;
+
+	/* allocate message with maximum possible size */
+	len = strlen(action_string) + strlen(devpath) + 2;
+	skb = alloc_skb(len + env->buflen, GFP_KERNEL);
+	if (!skb)
+		return NULL;
+
+	/* add header */
+	scratch = skb_put(skb, len);
+	sprintf(scratch, "%s@%s", action_string, devpath);
+
+	skb_put_data(skb, env->buf, env->buflen);
+
+	parms = &NETLINK_CB(skb);
+	parms->creds.uid = GLOBAL_ROOT_UID;
+	parms->creds.gid = GLOBAL_ROOT_GID;
+	parms->dst_group = 1;
+	parms->portid = 0;
+
+	return skb;
+}
+
+static int uevent_net_broadcast_untagged(struct kobj_uevent_env *env,
+					 const char *action_string,
+					 const char *devpath)
+{
+	struct sk_buff *skb = NULL;
+	struct uevent_sock *ue_sk;
+	int retval = 0;
+
+	/* send netlink message */
+	mutex_lock(&uevent_sock_mutex);
+	list_for_each_entry(ue_sk, &uevent_sock_list, list) {
+		struct sock *uevent_sock = ue_sk->sk;
+
+		if (!netlink_has_listeners(uevent_sock, 1))
+			continue;
+
+		if (!skb) {
+			retval = -ENOMEM;
+			skb = alloc_uevent_skb(env, action_string, devpath);
+			if (!skb)
+				continue;
+		}
+
+		retval = netlink_broadcast(uevent_sock, skb_get(skb), 0, 1,
+					   GFP_KERNEL);
+		/* ENOBUFS should be handled in userspace */
+		if (retval == -ENOBUFS || retval == -ESRCH)
+			retval = 0;
+	}
+	mutex_unlock(&uevent_sock_mutex);
+	consume_skb(skb);
+
+	return retval;
+}
+
+static int uevent_net_broadcast_tagged(struct sock *usk,
+				       struct kobj_uevent_env *env,
+				       const char *action_string,
+				       const char *devpath)
+{
+	struct user_namespace *owning_user_ns = sock_net(usk)->user_ns;
+	struct sk_buff *skb = NULL;
+	int ret = 0;
+
+	skb = alloc_uevent_skb(env, action_string, devpath);
+	if (!skb)
+		return -ENOMEM;
+
+	/* fix credentials */
+	if (owning_user_ns != &init_user_ns) {
+		struct netlink_skb_parms *parms = &NETLINK_CB(skb);
+		kuid_t root_uid;
+		kgid_t root_gid;
+
+		/* fix uid */
+		root_uid = make_kuid(owning_user_ns, 0);
+		if (uid_valid(root_uid))
+			parms->creds.uid = root_uid;
+
+		/* fix gid */
+		root_gid = make_kgid(owning_user_ns, 0);
+		if (gid_valid(root_gid))
+			parms->creds.gid = root_gid;
+	}
+
+	ret = netlink_broadcast(usk, skb, 0, 1, GFP_KERNEL);
+	/* ENOBUFS should be handled in userspace */
+	if (ret == -ENOBUFS || ret == -ESRCH)
+		ret = 0;
+
+	return ret;
+}
+#endif
+
+static int kobject_uevent_net_broadcast(struct kobject *kobj,
+					struct kobj_uevent_env *env,
+					const char *action_string,
+					const char *devpath)
+{
+	int ret = 0;
+
+#ifdef CONFIG_NET
+	const struct kobj_ns_type_operations *ops;
+	const struct ns_common *ns = NULL;
+
+	ops = kobj_ns_ops(kobj);
+	if (!ops && kobj->kset) {
+		struct kobject *ksobj = &kobj->kset->kobj;
+
+		if (ksobj->parent != NULL)
+			ops = kobj_ns_ops(ksobj->parent);
+	}
+
+	/* kobjects currently only carry network namespace tags and they
+	 * are the only tag relevant here since we want to decide which
+	 * network namespaces to broadcast the uevent into.
+	 */
+	if (ops && ops->netlink_ns && kobj->ktype->namespace)
+		if (ops->type == KOBJ_NS_TYPE_NET)
+			ns = kobj->ktype->namespace(kobj);
+
+	if (!ns)
+		ret = uevent_net_broadcast_untagged(env, action_string,
+						    devpath);
+	else {
+		const struct net *net = container_of(ns, struct net, ns);
+
+		ret = uevent_net_broadcast_tagged(net->uevent_sock->sk, env,
+						  action_string, devpath);
+	}
+#endif
+
+	return ret;
+}
+
+static void zap_modalias_env(struct kobj_uevent_env *env)
+{
+	static const char modalias_prefix[] = "MODALIAS=";
+	size_t len;
+	int i, j;
+
+	for (i = 0; i < env->envp_idx;) {
+		if (strncmp(env->envp[i], modalias_prefix,
+			    sizeof(modalias_prefix) - 1)) {
+			i++;
+			continue;
+		}
+
+		len = strlen(env->envp[i]) + 1;
+
+		if (i != env->envp_idx - 1) {
+			/* @env->envp[] contains pointers to @env->buf[]
+			 * with @env->buflen chars, and we are removing
+			 * variable MODALIAS here pointed by @env->envp[i]
+			 * with length @len as shown below:
+			 *
+			 * 0               @env->buf[]      @env->buflen
+			 * ---------------------------------------------
+			 * ^             ^              ^              ^
+			 * |             |->   @len   <-| target block |
+			 * @env->envp[0] @env->envp[i]  @env->envp[i + 1]
+			 *
+			 * so the "target block" indicated above is moved
+			 * backward by @len, and its right size is
+			 * @env->buflen - (@env->envp[i + 1] - @env->envp[0]).
+			 */
+			memmove(env->envp[i], env->envp[i + 1],
+				env->buflen - (env->envp[i + 1] - env->envp[0]));
+
+			for (j = i; j < env->envp_idx - 1; j++)
+				env->envp[j] = env->envp[j + 1] - len;
+		}
+
+		env->envp_idx--;
+		env->buflen -= len;
+	}
+}
+
+/**
+ * kobject_uevent_env - send an uevent with environmental data
+ *
+ * @kobj: struct kobject that the action is happening to
+ * @action: action that is happening
+ * @envp_ext: pointer to environmental data
+ *
+ * Returns 0 if kobject_uevent_env() is completed with success or the
+ * corresponding error when it fails.
+ */
+int kobject_uevent_env(struct kobject *kobj, enum kobject_action action,
+		       char *envp_ext[])
+{
+	struct kobj_uevent_env *env;
+	const char *action_string = kobject_actions[action];
+	const char *devpath = NULL;
+	const char *subsystem;
+	struct kobject *top_kobj;
+	struct kset *kset;
+	const struct kset_uevent_ops *uevent_ops;
+	int i = 0;
+	int retval = 0;
+
+	/*
+	 * Mark "remove" event done regardless of result, for some subsystems
+	 * do not want to re-trigger "remove" event via automatic cleanup.
+	 */
+	if (action == KOBJ_REMOVE)
+		kobj->state_remove_uevent_sent = 1;
+
+	pr_debug("kobject: '%s' (%p): %s\n",
+		 kobject_name(kobj), kobj, __func__);
+
+	/* search the kset we belong to */
+	top_kobj = kobj;
+	while (!top_kobj->kset && top_kobj->parent)
+		top_kobj = top_kobj->parent;
+
+	if (!top_kobj->kset) {
+		pr_debug("kobject: '%s' (%p): %s: attempted to send uevent "
+			 "without kset!\n", kobject_name(kobj), kobj,
+			 __func__);
+		return -EINVAL;
+	}
+
+	kset = top_kobj->kset;
+	uevent_ops = kset->uevent_ops;
+
+	/* skip the event, if uevent_suppress is set*/
+	if (kobj->uevent_suppress) {
+		pr_debug("kobject: '%s' (%p): %s: uevent_suppress "
+				 "caused the event to drop!\n",
+				 kobject_name(kobj), kobj, __func__);
+		return 0;
+	}
+	/* skip the event, if the filter returns zero. */
+	if (uevent_ops && uevent_ops->filter)
+		if (!uevent_ops->filter(kobj)) {
+			pr_debug("kobject: '%s' (%p): %s: filter function "
+				 "caused the event to drop!\n",
+				 kobject_name(kobj), kobj, __func__);
+			return 0;
+		}
+
+	/* originating subsystem */
+	if (uevent_ops && uevent_ops->name)
+		subsystem = uevent_ops->name(kobj);
+	else
+		subsystem = kobject_name(&kset->kobj);
+	if (!subsystem) {
+		pr_debug("kobject: '%s' (%p): %s: unset subsystem caused the "
+			 "event to drop!\n", kobject_name(kobj), kobj,
+			 __func__);
+		return 0;
+	}
+
+	/* environment buffer */
+	env = kzalloc_obj(struct kobj_uevent_env);
+	if (!env)
+		return -ENOMEM;
+
+	/* complete object path */
+	devpath = kobject_get_path(kobj, GFP_KERNEL);
+	if (!devpath) {
+		retval = -ENOENT;
+		goto exit;
+	}
+
+	/* default keys */
+	retval = add_uevent_var(env, "ACTION=%s", action_string);
+	if (retval)
+		goto exit;
+	retval = add_uevent_var(env, "DEVPATH=%s", devpath);
+	if (retval)
+		goto exit;
+	retval = add_uevent_var(env, "SUBSYSTEM=%s", subsystem);
+	if (retval)
+		goto exit;
+
+	/* keys passed in from the caller */
+	if (envp_ext) {
+		for (i = 0; envp_ext[i]; i++) {
+			retval = add_uevent_var(env, "%s", envp_ext[i]);
+			if (retval)
+				goto exit;
+		}
+	}
+
+	/* let the kset specific function add its stuff */
+	if (uevent_ops && uevent_ops->uevent) {
+		retval = uevent_ops->uevent(kobj, env);
+		if (retval) {
+			pr_debug("kobject: '%s' (%p): %s: uevent() returned "
+				 "%d\n", kobject_name(kobj), kobj,
+				 __func__, retval);
+			goto exit;
+		}
+	}
+
+	switch (action) {
+	case KOBJ_ADD:
+		/*
+		 * Mark "add" event so we can make sure we deliver "remove"
+		 * event to userspace during automatic cleanup. If
+		 * the object did send an "add" event, "remove" will
+		 * automatically generated by the core, if not already done
+		 * by the caller.
+		 */
+		kobj->state_add_uevent_sent = 1;
+		break;
+
+	case KOBJ_UNBIND:
+		zap_modalias_env(env);
+		break;
+
+	default:
+		break;
+	}
+
+	/* we will send an event, so request a new sequence number */
+	retval = add_uevent_var(env, "SEQNUM=%llu",
+				atomic64_inc_return(&uevent_seqnum));
+	if (retval)
+		goto exit;
+
+	retval = kobject_uevent_net_broadcast(kobj, env, action_string,
+					      devpath);
+
+#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;
+
+		retval = add_uevent_var(env, "HOME=/");
+		if (retval)
+			goto exit;
+		retval = add_uevent_var(env,
+					"PATH=/sbin:/bin:/usr/sbin:/usr/bin");
+		if (retval)
+			goto exit;
+		retval = init_uevent_argv(env, subsystem);
+		if (retval)
+			goto exit;
+
+		retval = -ENOMEM;
+		info = call_usermodehelper_setup(env->argv[0], env->argv,
+						 env->envp, GFP_KERNEL,
+						 NULL, cleanup_uevent_env, env);
+		if (info) {
+			retval = call_usermodehelper_exec(info, UMH_NO_WAIT);
+			env = NULL;	/* freed by cleanup_uevent_env */
+		}
+	}
+#endif
+
+exit:
+	kfree(devpath);
+	kfree(env);
+	return retval;
+}
+EXPORT_SYMBOL_GPL(kobject_uevent_env);
+
+/**
+ * kobject_uevent - notify userspace by sending an uevent
+ *
+ * @kobj: struct kobject that the action is happening to
+ * @action: action that is happening
+ *
+ * Returns 0 if kobject_uevent() is completed with success or the
+ * corresponding error when it fails.
+ */
+int kobject_uevent(struct kobject *kobj, enum kobject_action action)
+{
+	return kobject_uevent_env(kobj, action, NULL);
+}
+EXPORT_SYMBOL_GPL(kobject_uevent);
+
+/**
+ * add_uevent_var - add key value string to the environment buffer
+ * @env: environment buffer structure
+ * @format: printf format for the key=value pair
+ *
+ * Returns 0 if environment variable was added successfully or -ENOMEM
+ * if no space was available.
+ */
+int add_uevent_var(struct kobj_uevent_env *env, const char *format, ...)
+{
+	va_list args;
+	int len;
+
+	if (env->envp_idx >= ARRAY_SIZE(env->envp)) {
+		WARN(1, KERN_ERR "add_uevent_var: too many keys\n");
+		return -ENOMEM;
+	}
+
+	va_start(args, format);
+	len = vsnprintf(&env->buf[env->buflen],
+			sizeof(env->buf) - env->buflen,
+			format, args);
+	va_end(args);
+
+	if (len >= (sizeof(env->buf) - env->buflen)) {
+		WARN(1, KERN_ERR "add_uevent_var: buffer size too small\n");
+		return -ENOMEM;
+	}
+
+	env->envp[env->envp_idx++] = &env->buf[env->buflen];
+	env->buflen += len + 1;
+	return 0;
+}
+EXPORT_SYMBOL_GPL(add_uevent_var);
+
+#if defined(CONFIG_NET)
+static int uevent_net_broadcast(struct sock *usk, struct sk_buff *skb,
+				struct netlink_ext_ack *extack)
+{
+	/* u64 to chars: 2^64 - 1 = 21 chars */
+	char buf[sizeof("SEQNUM=") + 21];
+	struct sk_buff *skbc;
+	int ret;
+
+	/* bump and prepare sequence number */
+	ret = snprintf(buf, sizeof(buf), "SEQNUM=%llu",
+		       atomic64_inc_return(&uevent_seqnum));
+	if (ret < 0 || (size_t)ret >= sizeof(buf))
+		return -ENOMEM;
+	ret++;
+
+	/* verify message does not overflow */
+	if ((skb->len + ret) > UEVENT_BUFFER_SIZE) {
+		NL_SET_ERR_MSG(extack, "uevent message too big");
+		return -EINVAL;
+	}
+
+	/* copy skb and extend to accommodate sequence number */
+	skbc = skb_copy_expand(skb, 0, ret, GFP_KERNEL);
+	if (!skbc)
+		return -ENOMEM;
+
+	/* append sequence number */
+	skb_put_data(skbc, buf, ret);
+
+	/* remove msg header */
+	skb_pull(skbc, NLMSG_HDRLEN);
+
+	/* set portid 0 to inform userspace message comes from kernel */
+	NETLINK_CB(skbc).portid = 0;
+	NETLINK_CB(skbc).dst_group = 1;
+
+	ret = netlink_broadcast(usk, skbc, 0, 1, GFP_KERNEL);
+	/* ENOBUFS should be handled in userspace */
+	if (ret == -ENOBUFS || ret == -ESRCH)
+		ret = 0;
+
+	return ret;
+}
+
+static int uevent_net_rcv_skb(struct sk_buff *skb, struct nlmsghdr *nlh,
+			      struct netlink_ext_ack *extack)
+{
+	struct net *net;
+	int ret;
+
+	if (!nlmsg_data(nlh))
+		return -EINVAL;
+
+	/*
+	 * Verify that we are allowed to send messages to the target
+	 * network namespace. The caller must have CAP_SYS_ADMIN in the
+	 * owning user namespace of the target network namespace.
+	 */
+	net = sock_net(NETLINK_CB(skb).sk);
+	if (!netlink_ns_capable(skb, net->user_ns, CAP_SYS_ADMIN)) {
+		NL_SET_ERR_MSG(extack, "missing CAP_SYS_ADMIN capability");
+		return -EPERM;
+	}
+
+	ret = uevent_net_broadcast(net->uevent_sock->sk, skb, extack);
+
+	return ret;
+}
+
+static void uevent_net_rcv(struct sk_buff *skb)
+{
+	netlink_rcv_skb(skb, &uevent_net_rcv_skb);
+}
+
+static int uevent_net_init(struct net *net)
+{
+	struct uevent_sock *ue_sk;
+	struct netlink_kernel_cfg cfg = {
+		.groups	= 1,
+		.input = uevent_net_rcv,
+		.flags	= NL_CFG_F_NONROOT_RECV
+	};
+
+	ue_sk = kzalloc_obj(*ue_sk);
+	if (!ue_sk)
+		return -ENOMEM;
+
+	ue_sk->sk = netlink_kernel_create(net, NETLINK_KOBJECT_UEVENT, &cfg);
+	if (!ue_sk->sk) {
+		pr_err("kobject_uevent: unable to create netlink socket!\n");
+		kfree(ue_sk);
+		return -ENODEV;
+	}
+
+	net->uevent_sock = ue_sk;
+
+	/* Restrict uevents to initial user namespace. */
+	if (sock_net(ue_sk->sk)->user_ns == &init_user_ns) {
+		mutex_lock(&uevent_sock_mutex);
+		list_add_tail(&ue_sk->list, &uevent_sock_list);
+		mutex_unlock(&uevent_sock_mutex);
+	}
+
+	return 0;
+}
+
+static void uevent_net_exit(struct net *net)
+{
+	struct uevent_sock *ue_sk = net->uevent_sock;
+
+	if (sock_net(ue_sk->sk)->user_ns == &init_user_ns) {
+		mutex_lock(&uevent_sock_mutex);
+		list_del(&ue_sk->list);
+		mutex_unlock(&uevent_sock_mutex);
+	}
+
+	netlink_kernel_release(ue_sk->sk);
+	kfree(ue_sk);
+}
+
+static struct pernet_operations uevent_net_ops = {
+	.init	= uevent_net_init,
+	.exit	= uevent_net_exit,
+};
+
+static int __init kobject_uevent_init(void)
+{
+	return register_pernet_subsys(&uevent_net_ops);
+}
+
+
+postcore_initcall(kobject_uevent_init);
+#endif
+
+#ifdef CONFIG_UEVENT_HELPER
+static const struct ctl_table uevent_helper_sysctl_table[] = {
+	{
+		.procname	= "hotplug",
+		.data		= &uevent_helper,
+		.maxlen		= UEVENT_HELPER_PATH_LEN,
+		.mode		= 0644,
+		.proc_handler	= proc_dostring,
+	},
+};
+
+static int __init init_uevent_helper_sysctl(void)
+{
+	register_sysctl_init("kernel", uevent_helper_sysctl_table);
+	return 0;
+}
+
+postcore_initcall(init_uevent_helper_sysctl);
+#endif