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linux-next/lib/kobject_uevent.c
Christian Brauner a3498436b3 netns: restrict uevents 
commit 07e98962fa ("kobject: Send hotplug events in all network namespaces")

enabled sending hotplug events into all network namespaces back in 2010.
Over time the set of uevents that get sent into all network namespaces has
shrunk. We have now reached the point where hotplug events for all devices
that carry a namespace tag are filtered according to that namespace.
Specifically, they are filtered whenever the namespace tag of the kobject
does not match the namespace tag of the netlink socket.
Currently, only network devices carry namespace tags (i.e. network
namespace tags). Hence, uevents for network devices only show up in the
network namespace such devices are created in or moved to.

However, any uevent for a kobject that does not have a namespace tag
associated with it will not be filtered and we will broadcast it into all
network namespaces. This behavior stopped making sense when user namespaces
were introduced.

This patch simplifies and fixes couple of things:
- Split codepath for sending uevents by kobject namespace tags:
  1. Untagged kobjects - uevent_net_broadcast_untagged():
     Untagged kobjects will be broadcast into all uevent sockets recorded
     in uevent_sock_list, i.e. into all network namespacs owned by the
     intial user namespace.
  2. Tagged kobjects - uevent_net_broadcast_tagged():
     Tagged kobjects will only be broadcast into the network namespace they
     were tagged with.
  Handling of tagged kobjects in 2. does not cause any semantic changes.
  This is just splitting out the filtering logic that was handled by
  kobj_bcast_filter() before.
  Handling of untagged kobjects in 1. will cause a semantic change. The
  reasons why this is needed and ok have been discussed in [1]. Here is a
  short summary:
  - Userspace ignores uevents from network namespaces that are not owned by
    the intial user namespace:
    Uevents are filtered by userspace in a user namespace because the
    received uid != 0. Instead the uid associated with the event will be
    65534 == "nobody" because the global root uid is not mapped.
    This means we can safely and without introducing regressions modify the
    kernel to not send uevents into all network namespaces whose owning
    user namespace is not the initial user namespace because we know that
    userspace will ignore the message because of the uid anyway.
    I have a) verified that is is true for every udev implementation out
    there b) that this behavior has been present in all udev
    implementations from the very beginning.
  - Thundering herd:
    Broadcasting uevents into all network namespaces introduces significant
    overhead.
    All processes that listen to uevents running in non-initial user
    namespaces will end up responding to uevents that will be meaningless
    to them. Mainly, because non-initial user namespaces cannot easily
    manage devices unless they have a privileged host-process helping them
    out. This means that there will be a thundering herd of activity when
    there shouldn't be any.
  - Removing needless overhead/Increasing performance:
    Currently, the uevent socket for each network namespace is added to the
    global variable uevent_sock_list. The list itself needs to be protected
    by a mutex. So everytime a uevent is generated the mutex is taken on
    the list. The mutex is held *from the creation of the uevent (memory
    allocation, string creation etc. until all uevent sockets have been
    handled*. This is aggravated by the fact that for each uevent socket
    that has listeners the mc_list must be walked as well which means we're
    talking O(n^2) here. Given that a standard Linux workload usually has
    quite a lot of network namespaces and - in the face of containers - a
    lot of user namespaces this quickly becomes a performance problem (see
    "Thundering herd" above). By just recording uevent sockets of network
    namespaces that are owned by the initial user namespace we
    significantly increase performance in this codepath.
  - Injecting uevents:
    There's a valid argument that containers might be interested in
    receiving device events especially if they are delegated to them by a
    privileged userspace process. One prime example are SR-IOV enabled
    devices that are explicitly designed to be handed of to other users
    such as VMs or containers.
    This use-case can now be correctly handled since
    commit 692ec06d7c ("netns: send uevent messages"). This commit
    introduced the ability to send uevents from userspace. As such we can
    let a sufficiently privileged (CAP_SYS_ADMIN in the owning user
    namespace of the network namespace of the netlink socket) userspace
    process make a decision what uevents should be sent. This removes the
    need to blindly broadcast uevents into all user namespaces and provides
    a performant and safe solution to this problem.
  - Filtering logic:
    This patch filters by *owning user namespace of the network namespace a
    given task resides in* and not by user namespace of the task per se.
    This means if the user namespace of a given task is unshared but the
    network namespace is kept and is owned by the initial user namespace a
    listener that is opening the uevent socket in that network namespace
    can still listen to uevents.
- Fix permission for tagged kobjects:
  Network devices that are created or moved into a network namespace that
  is owned by a non-initial user namespace currently are send with
  INVALID_{G,U}ID in their credentials. This means that all current udev
  implementations in userspace will ignore the uevent they receive for
  them. This has lead to weird bugs whereby new devices showing up in such
  network namespaces were not recognized and did not get IPs assigned etc.
  This patch adjusts the permission to the appropriate {g,u}id in the
  respective user namespace. This way udevd is able to correctly handle
  such devices.
- Simplify filtering logic:
  do_one_broadcast() already ensures that only listeners in mc_list receive
  uevents that have the same network namespace as the uevent socket itself.
  So the filtering logic in kobj_bcast_filter is not needed (see [3]). This
  patch therefore removes kobj_bcast_filter() and replaces
  netlink_broadcast_filtered() with the simpler netlink_broadcast()
  everywhere.

[1]: https://lkml.org/lkml/2018/4/4/739
[2]: https://lkml.org/lkml/2018/4/26/767
[3]: https://lkml.org/lkml/2018/4/26/738
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2018-05-01 10:22:41 -04:00

811 lines
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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\n";
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\n";
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);
printk(KERN_WARNING "synth uevent: %s: %s",
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 len;
len = strlcpy(&env->buf[env->buflen], subsystem,
sizeof(env->buf) - env->buflen);
if (len >= (sizeof(env->buf) - env->buflen)) {
WARN(1, KERN_ERR "init_uevent_argv: buffer size too small\n");
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;
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_REMOVE:
kobj->state_remove_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", (unsigned long long)++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) {
printk(KERN_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
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