// 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 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;

        /*
         * 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