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// 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>
u64 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);
#endif
/* This lock protects uevent_seqnum and uevent_sock_list */
static DEFINE_MUTEX(uevent_sock_mutex);
/* 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(sizeof(*env), GFP_KERNEL);
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 void *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 = strlcpy(&env->buf[env->buflen], subsystem, buffer_size);
if (len >= buffer_size) {
pr_warn("init_uevent_argv: buffer size of %d too small, needed %d\n",
buffer_size, len);
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 */
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;
}
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 net *net = 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)
net = kobj->ktype->namespace(kobj);
if (!net)
ret = uevent_net_broadcast_untagged(env, action_string,
devpath);
else
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) {
memmove(env->envp[i], env->envp[i + 1],
env->buflen - len);
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(kset, 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(kset, 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(sizeof(struct kobj_uevent_env), GFP_KERNEL);
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(kset, 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;
}
mutex_lock(&uevent_sock_mutex);
/* we will send an event, so request a new sequence number */
retval = add_uevent_var(env, "SEQNUM=%llu", ++uevent_seqnum);
if (retval) {
mutex_unlock(&uevent_sock_mutex);
goto exit;
}
retval = kobject_uevent_net_broadcast(kobj, env, action_string,
devpath);
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;
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", ++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;
}
mutex_lock(&uevent_sock_mutex);
ret = uevent_net_broadcast(net->uevent_sock->sk, skb, extack);
mutex_unlock(&uevent_sock_mutex);
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(sizeof(*ue_sk), GFP_KERNEL);
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