// SPDX-License-Identifier: GPL-2.0
/*
 * NETLINK      Generic Netlink Family
 *
 *              Authors:        Jamal Hadi Salim
 *                              Thomas Graf <tgraf@suug.ch>
 *                              Johannes Berg <johannes@sipsolutions.net>
 */

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/errno.h>
#include <linux/types.h>
#include <linux/socket.h>
#include <linux/string.h>
#include <linux/skbuff.h>
#include <linux/mutex.h>
#include <linux/bitmap.h>
#include <linux/rwsem.h>
#include <linux/idr.h>
#include <net/sock.h>
#include <net/genetlink.h>

static DEFINE_MUTEX(genl_mutex); /* serialization of message processing */
static DECLARE_RWSEM(cb_lock);

atomic_t genl_sk_destructing_cnt = ATOMIC_INIT(0);
DECLARE_WAIT_QUEUE_HEAD(genl_sk_destructing_waitq);

void genl_lock(void)
{
        mutex_lock(&genl_mutex);
}
EXPORT_SYMBOL(genl_lock);

void genl_unlock(void)
{
        mutex_unlock(&genl_mutex);
}
EXPORT_SYMBOL(genl_unlock);

#ifdef CONFIG_LOCKDEP
bool lockdep_genl_is_held(void)
{
        return lockdep_is_held(&genl_mutex);
}
EXPORT_SYMBOL(lockdep_genl_is_held);
#endif

static void genl_lock_all(void)
{
        down_write(&cb_lock);
        genl_lock();
}

static void genl_unlock_all(void)
{
        genl_unlock();
        up_write(&cb_lock);
}

static DEFINE_IDR(genl_fam_idr);

/*
 * Bitmap of multicast groups that are currently in use.
 *
 * To avoid an allocation at boot of just one unsigned long,
 * declare it global instead.
 * Bit 0 is marked as already used since group 0 is invalid.
 * Bit 1 is marked as already used since the drop-monitor code
 * abuses the API and thinks it can statically use group 1.
 * That group will typically conflict with other groups that
 * any proper users use.
 * Bit 16 is marked as used since it's used for generic netlink
 * and the code no longer marks pre-reserved IDs as used.
 * Bit 17 is marked as already used since the VFS quota code
 * also abused this API and relied on family == group ID, we
 * cater to that by giving it a static family and group ID.
 * Bit 18 is marked as already used since the PMCRAID driver
 * did the same thing as the VFS quota code (maybe copied?)
 */
static unsigned long mc_group_start = 0x3 | BIT(GENL_ID_CTRL) |
                                      BIT(GENL_ID_VFS_DQUOT) |
                                      BIT(GENL_ID_PMCRAID);
static unsigned long *mc_groups = &mc_group_start;
static unsigned long mc_groups_longs = 1;

static int genl_ctrl_event(int event, const struct genl_family *family,
                           const struct genl_multicast_group *grp,
                           int grp_id);

static const struct genl_family *genl_family_find_byid(unsigned int id)
{
        return idr_find(&genl_fam_idr, id);
}

static const struct genl_family *genl_family_find_byname(char *name)
{
        const struct genl_family *family;
        unsigned int id;

        idr_for_each_entry(&genl_fam_idr, family, id)
                if (strcmp(family->name, name) == 0)
                        return family;

        return NULL;
}

static const struct genl_ops *genl_get_cmd(u8 cmd,
                                           const struct genl_family *family)
{
        int i;

        for (i = 0; i < family->n_ops; i++)
                if (family->ops[i].cmd == cmd)
                        return &family->ops[i];

        return NULL;
}

static int genl_allocate_reserve_groups(int n_groups, int *first_id)
{
        unsigned long *new_groups;
        int start = 0;
        int i;
        int id;
        bool fits;

        do {
                if (start == 0)
                        id = find_first_zero_bit(mc_groups,
                                                 mc_groups_longs *
                                                 BITS_PER_LONG);
                else
                        id = find_next_zero_bit(mc_groups,
                                                mc_groups_longs * BITS_PER_LONG,
                                                start);

                fits = true;
                for (i = id;
                     i < min_t(int, id + n_groups,
                               mc_groups_longs * BITS_PER_LONG);
                     i++) {
                        if (test_bit(i, mc_groups)) {
                                start = i;
                                fits = false;
                                break;
                        }
                }

                if (id + n_groups > mc_groups_longs * BITS_PER_LONG) {
                        unsigned long new_longs = mc_groups_longs +
                                                  BITS_TO_LONGS(n_groups);
                        size_t nlen = new_longs * sizeof(unsigned long);

                        if (mc_groups == &mc_group_start) {
                                new_groups = kzalloc(nlen, GFP_KERNEL);
                                if (!new_groups)
                                        return -ENOMEM;
                                mc_groups = new_groups;
                                *mc_groups = mc_group_start;
                        } else {
                                new_groups = krealloc(mc_groups, nlen,
                                                      GFP_KERNEL);
                                if (!new_groups)
                                        return -ENOMEM;
                                mc_groups = new_groups;
                                for (i = 0; i < BITS_TO_LONGS(n_groups); i++)
                                        mc_groups[mc_groups_longs + i] = 0;
                        }
                        mc_groups_longs = new_longs;
                }
        } while (!fits);

        for (i = id; i < id + n_groups; i++)
                set_bit(i, mc_groups);
        *first_id = id;
        return 0;
}

static struct genl_family genl_ctrl;

static int genl_validate_assign_mc_groups(struct genl_family *family)
{
        int first_id;
        int n_groups = family->n_mcgrps;
        int err = 0, i;
        bool groups_allocated = false;

        if (!n_groups)
                return 0;

        for (i = 0; i < n_groups; i++) {
                const struct genl_multicast_group *grp = &family->mcgrps[i];

                if (WARN_ON(grp->name[0] == '\0'))
                        return -EINVAL;
                if (WARN_ON(memchr(grp->name, '\0', GENL_NAMSIZ) == NULL))
                        return -EINVAL;
        }

        /* special-case our own group and hacks */
        if (family == &genl_ctrl) {
                first_id = GENL_ID_CTRL;
                BUG_ON(n_groups != 1);
        } else if (strcmp(family->name, "NET_DM") == 0) {
                first_id = 1;
                BUG_ON(n_groups != 1);
        } else if (family->id == GENL_ID_VFS_DQUOT) {
                first_id = GENL_ID_VFS_DQUOT;
                BUG_ON(n_groups != 1);
        } else if (family->id == GENL_ID_PMCRAID) {
                first_id = GENL_ID_PMCRAID;
                BUG_ON(n_groups != 1);
        } else {
                groups_allocated = true;
                err = genl_allocate_reserve_groups(n_groups, &first_id);
                if (err)
                        return err;
        }

        family->mcgrp_offset = first_id;

        /* if still initializing, can't and don't need to to realloc bitmaps */
        if (!init_net.genl_sock)
                return 0;

        if (family->netnsok) {
                struct net *net;

                netlink_table_grab();
                rcu_read_lock();
                for_each_net_rcu(net) {
                        err = __netlink_change_ngroups(net->genl_sock,
                                        mc_groups_longs * BITS_PER_LONG);
                        if (err) {
                                /*
                                 * No need to roll back, can only fail if
                                 * memory allocation fails and then the
                                 * number of _possible_ groups has been
                                 * increased on some sockets which is ok.
                                 */
                                break;
                        }
                }
                rcu_read_unlock();
                netlink_table_ungrab();
        } else {
                err = netlink_change_ngroups(init_net.genl_sock,
                                             mc_groups_longs * BITS_PER_LONG);
        }

        if (groups_allocated && err) {
                for (i = 0; i < family->n_mcgrps; i++)
                        clear_bit(family->mcgrp_offset + i, mc_groups);
        }

        return err;
}

static void genl_unregister_mc_groups(const struct genl_family *family)
{
        struct net *net;
        int i;

        netlink_table_grab();
        rcu_read_lock();
        for_each_net_rcu(net) {
                for (i = 0; i < family->n_mcgrps; i++)
                        __netlink_clear_multicast_users(
                                net->genl_sock, family->mcgrp_offset + i);
        }
        rcu_read_unlock();
        netlink_table_ungrab();

        for (i = 0; i < family->n_mcgrps; i++) {
                int grp_id = family->mcgrp_offset + i;

                if (grp_id != 1)
                        clear_bit(grp_id, mc_groups);
                genl_ctrl_event(CTRL_CMD_DELMCAST_GRP, family,
                                &family->mcgrps[i], grp_id);
        }
}

static int genl_validate_ops(const struct genl_family *family)
{
        const struct genl_ops *ops = family->ops;
        unsigned int n_ops = family->n_ops;
        int i, j;

        if (WARN_ON(n_ops && !ops))
                return -EINVAL;

        if (!n_ops)
                return 0;

        for (i = 0; i < n_ops; i++) {
                if (ops[i].dumpit == NULL && ops[i].doit == NULL)
                        return -EINVAL;
                for (j = i + 1; j < n_ops; j++)
                        if (ops[i].cmd == ops[j].cmd)
                                return -EINVAL;
        }

        return 0;
}

/**
 * genl_register_family - register a generic netlink family
 * @family: generic netlink family
 *
 * Registers the specified family after validating it first. Only one
 * family may be registered with the same family name or identifier.
 *
 * The family's ops, multicast groups and module pointer must already
 * be assigned.
 *
 * Return 0 on success or a negative error code.
 */
int genl_register_family(struct genl_family *family)
{
        int err, i;
        int start = GENL_START_ALLOC, end = GENL_MAX_ID;

        err = genl_validate_ops(family);
        if (err)
                return err;

        genl_lock_all();

        if (genl_family_find_byname(family->name)) {
                err = -EEXIST;
                goto errout_locked;
        }

        /*
         * Sadly, a few cases need to be special-cased
         * due to them having previously abused the API
         * and having used their family ID also as their
         * multicast group ID, so we use reserved IDs
         * for both to be sure we can do that mapping.
         */
        if (family == &genl_ctrl) {
                /* and this needs to be special for initial family lookups */
                start = end = GENL_ID_CTRL;
        } else if (strcmp(family->name, "pmcraid") == 0) {
                start = end = GENL_ID_PMCRAID;
        } else if (strcmp(family->name, "VFS_DQUOT") == 0) {
                start = end = GENL_ID_VFS_DQUOT;
        }

        if (family->maxattr && !family->parallel_ops) {
                family->attrbuf = kmalloc_array(family->maxattr + 1,
                                                sizeof(struct nlattr *),
                                                GFP_KERNEL);
                if (family->attrbuf == NULL) {
                        err = -ENOMEM;
                        goto errout_locked;
                }
        } else
                family->attrbuf = NULL;

        family->id = idr_alloc_cyclic(&genl_fam_idr, family,
                                      start, end + 1, GFP_KERNEL);
        if (family->id < 0) {
                err = family->id;
                goto errout_free;
        }

        err = genl_validate_assign_mc_groups(family);
        if (err)
                goto errout_remove;

        genl_unlock_all();

        /* send all events */
        genl_ctrl_event(CTRL_CMD_NEWFAMILY, family, NULL, 0);
        for (i = 0; i < family->n_mcgrps; i++)
                genl_ctrl_event(CTRL_CMD_NEWMCAST_GRP, family,
                                &family->mcgrps[i], family->mcgrp_offset + i);

        return 0;

errout_remove:
        idr_remove(&genl_fam_idr, family->id);
errout_free:
        kfree(family->attrbuf);
errout_locked:
        genl_unlock_all();
        return err;
}
EXPORT_SYMBOL(genl_register_family);

/**
 * genl_unregister_family - unregister generic netlink family
 * @family: generic netlink family
 *
 * Unregisters the specified family.
 *
 * Returns 0 on success or a negative error code.
 */
int genl_unregister_family(const struct genl_family *family)
{
        genl_lock_all();

        if (!genl_family_find_byid(family->id)) {
                genl_unlock_all();
                return -ENOENT;
        }

        genl_unregister_mc_groups(family);

        idr_remove(&genl_fam_idr, family->id);

        up_write(&cb_lock);
        wait_event(genl_sk_destructing_waitq,
                   atomic_read(&genl_sk_destructing_cnt) == 0);
        genl_unlock();

        kfree(family->attrbuf);

        genl_ctrl_event(CTRL_CMD_DELFAMILY, family, NULL, 0);

        return 0;
}
EXPORT_SYMBOL(genl_unregister_family);

/**
 * genlmsg_put - Add generic netlink header to netlink message
 * @skb: socket buffer holding the message
 * @portid: netlink portid the message is addressed to
 * @seq: sequence number (usually the one of the sender)
 * @family: generic netlink family
 * @flags: netlink message flags
 * @cmd: generic netlink command
 *
 * Returns pointer to user specific header
 */
void *genlmsg_put(struct sk_buff *skb, u32 portid, u32 seq,
                  const struct genl_family *family, int flags, u8 cmd)
{
        struct nlmsghdr *nlh;
        struct genlmsghdr *hdr;

        nlh = nlmsg_put(skb, portid, seq, family->id, GENL_HDRLEN +
                        family->hdrsize, flags);
        if (nlh == NULL)
                return NULL;

        hdr = nlmsg_data(nlh);
        hdr->cmd = cmd;
        hdr->version = family->version;
        hdr->reserved = 0;

        return (char *) hdr + GENL_HDRLEN;
}
EXPORT_SYMBOL(genlmsg_put);

static int genl_lock_start(struct netlink_callback *cb)
{
        /* our ops are always const - netlink API doesn't propagate that */
        const struct genl_ops *ops = cb->data;
        int rc = 0;

        if (ops->start) {
                genl_lock();
                rc = ops->start(cb);
                genl_unlock();
        }
        return rc;
}

static int genl_lock_dumpit(struct sk_buff *skb, struct netlink_callback *cb)
{
        /* our ops are always const - netlink API doesn't propagate that */
        const struct genl_ops *ops = cb->data;
        int rc;

        genl_lock();
        rc = ops->dumpit(skb, cb);
        genl_unlock();
        return rc;
}

static int genl_lock_done(struct netlink_callback *cb)
{
        /* our ops are always const - netlink API doesn't propagate that */
        const struct genl_ops *ops = cb->data;
        int rc = 0;

        if (ops->done) {
                genl_lock();
                rc = ops->done(cb);
                genl_unlock();
        }
        return rc;
}

static int genl_family_rcv_msg(const struct genl_family *family,
                               struct sk_buff *skb,
                               struct nlmsghdr *nlh,
                               struct netlink_ext_ack *extack)
{
        const struct genl_ops *ops;
        struct net *net = sock_net(skb->sk);
        struct genl_info info;
        struct genlmsghdr *hdr = nlmsg_data(nlh);
        struct nlattr **attrbuf;
        int hdrlen, err;

        /* this family doesn't exist in this netns */
        if (!family->netnsok && !net_eq(net, &init_net))
                return -ENOENT;

        hdrlen = GENL_HDRLEN + family->hdrsize;
        if (nlh->nlmsg_len < nlmsg_msg_size(hdrlen))
                return -EINVAL;

        ops = genl_get_cmd(hdr->cmd, family);
        if (ops == NULL)
                return -EOPNOTSUPP;

        if ((ops->flags & GENL_ADMIN_PERM) &&
            !netlink_capable(skb, CAP_NET_ADMIN))
                return -EPERM;

        if ((ops->flags & GENL_UNS_ADMIN_PERM) &&
            !netlink_ns_capable(skb, net->user_ns, CAP_NET_ADMIN))
                return -EPERM;

        if ((nlh->nlmsg_flags & NLM_F_DUMP) == NLM_F_DUMP) {
                int rc;

                if (ops->dumpit == NULL)
                        return -EOPNOTSUPP;

                if (!(ops->validate & GENL_DONT_VALIDATE_DUMP)) {
                        int hdrlen = GENL_HDRLEN + family->hdrsize;

                        if (nlh->nlmsg_len < nlmsg_msg_size(hdrlen))
                                return -EINVAL;

                        if (family->maxattr) {
                                unsigned int validate = NL_VALIDATE_STRICT;

                                if (ops->validate &
                                    GENL_DONT_VALIDATE_DUMP_STRICT)
                                        validate = NL_VALIDATE_LIBERAL;
                                rc = __nla_validate(nlmsg_attrdata(nlh, hdrlen),
                                                    nlmsg_attrlen(nlh, hdrlen),
                                                    family->maxattr,
                                                    family->policy,
                                                    validate, extack);
                                if (rc)
                                        return rc;
                        }
                }

                if (!family->parallel_ops) {
                        struct netlink_dump_control c = {
                                .module = family->module,
                                /* we have const, but the netlink API doesn't */
                                .data = (void *)ops,
                                .start = genl_lock_start,
                                .dump = genl_lock_dumpit,
                                .done = genl_lock_done,
                        };

                        genl_unlock();
                        rc = __netlink_dump_start(net->genl_sock, skb, nlh, &c);
                        genl_lock();

                } else {
                        struct netlink_dump_control c = {
                                .module = family->module,
                                .start = ops->start,
                                .dump = ops->dumpit,
                                .done = ops->done,
                        };

                        rc = __netlink_dump_start(net->genl_sock, skb, nlh, &c);
                }

                return rc;
        }

        if (ops->doit == NULL)
                return -EOPNOTSUPP;

        if (family->maxattr && family->parallel_ops) {
                attrbuf = kmalloc_array(family->maxattr + 1,
                                        sizeof(struct nlattr *),
                                        GFP_KERNEL);
                if (attrbuf == NULL)
                        return -ENOMEM;
        } else
                attrbuf = family->attrbuf;

        if (attrbuf) {
                enum netlink_validation validate = NL_VALIDATE_STRICT;

                if (ops->validate & GENL_DONT_VALIDATE_STRICT)
                        validate = NL_VALIDATE_LIBERAL;

                err = __nlmsg_parse(nlh, hdrlen, attrbuf, family->maxattr,
                                    family->policy, validate, extack);
                if (err < 0)
                        goto out;
        }

        info.snd_seq = nlh->nlmsg_seq;
        info.snd_portid = NETLINK_CB(skb).portid;
        info.nlhdr = nlh;
        info.genlhdr = nlmsg_data(nlh);
        info.userhdr = nlmsg_data(nlh) + GENL_HDRLEN;
        info.attrs = attrbuf;
        info.extack = extack;
        genl_info_net_set(&info, net);
        memset(&info.user_ptr, 0, sizeof(info.user_ptr));

        if (family->pre_doit) {
                err = family->pre_doit(ops, skb, &info);
                if (err)
                        goto out;
        }

        err = ops->doit(skb, &info);

        if (family->post_doit)
                family->post_doit(ops, skb, &info);

out:
        if (family->parallel_ops)
                kfree(attrbuf);

        return err;
}

static int genl_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh,
                        struct netlink_ext_ack *extack)
{
        const struct genl_family *family;
        int err;

        family = genl_family_find_byid(nlh->nlmsg_type);
        if (family == NULL)
                return -ENOENT;

        if (!family->parallel_ops)
                genl_lock();

        err = genl_family_rcv_msg(family, skb, nlh, extack);

        if (!family->parallel_ops)
                genl_unlock();

        return err;
}

static void genl_rcv(struct sk_buff *skb)
{
        down_read(&cb_lock);
        netlink_rcv_skb(skb, &genl_rcv_msg);
        up_read(&cb_lock);
}

/**************************************************************************
 * Controller
 **************************************************************************/

static struct genl_family genl_ctrl;

static int ctrl_fill_info(const struct genl_family *family, u32 portid, u32 seq,
                          u32 flags, struct sk_buff *skb, u8 cmd)
{
        void *hdr;

        hdr = genlmsg_put(skb, portid, seq, &genl_ctrl, flags, cmd);
        if (hdr == NULL)
                return -1;

        if (nla_put_string(skb, CTRL_ATTR_FAMILY_NAME, family->name) ||
            nla_put_u16(skb, CTRL_ATTR_FAMILY_ID, family->id) ||
            nla_put_u32(skb, CTRL_ATTR_VERSION, family->version) ||
            nla_put_u32(skb, CTRL_ATTR_HDRSIZE, family->hdrsize) ||
            nla_put_u32(skb, CTRL_ATTR_MAXATTR, family->maxattr))
                goto nla_put_failure;

        if (family->n_ops) {
                struct nlattr *nla_ops;
                int i;

                nla_ops = nla_nest_start_noflag(skb, CTRL_ATTR_OPS);
                if (nla_ops == NULL)
                        goto nla_put_failure;

                for (i = 0; i < family->n_ops; i++) {
                        struct nlattr *nest;
                        const struct genl_ops *ops = &family->ops[i];
                        u32 op_flags = ops->flags;

                        if (ops->dumpit)
                                op_flags |= GENL_CMD_CAP_DUMP;
                        if (ops->doit)
                                op_flags |= GENL_CMD_CAP_DO;
                        if (family->policy)
                                op_flags |= GENL_CMD_CAP_HASPOL;

                        nest = nla_nest_start_noflag(skb, i + 1);
                        if (nest == NULL)
                                goto nla_put_failure;

                        if (nla_put_u32(skb, CTRL_ATTR_OP_ID, ops->cmd) ||
                            nla_put_u32(skb, CTRL_ATTR_OP_FLAGS, op_flags))
                                goto nla_put_failure;

                        nla_nest_end(skb, nest);
                }

                nla_nest_end(skb, nla_ops);
        }

        if (family->n_mcgrps) {
                struct nlattr *nla_grps;
                int i;

                nla_grps = nla_nest_start_noflag(skb, CTRL_ATTR_MCAST_GROUPS);
                if (nla_grps == NULL)
                        goto nla_put_failure;

                for (i = 0; i < family->n_mcgrps; i++) {
                        struct nlattr *nest;
                        const struct genl_multicast_group *grp;

                        grp = &family->mcgrps[i];

                        nest = nla_nest_start_noflag(skb, i + 1);
                        if (nest == NULL)
                                goto nla_put_failure;

                        if (nla_put_u32(skb, CTRL_ATTR_MCAST_GRP_ID,
                                        family->mcgrp_offset + i) ||
                            nla_put_string(skb, CTRL_ATTR_MCAST_GRP_NAME,
                                           grp->name))
                                goto nla_put_failure;

                        nla_nest_end(skb, nest);
                }
                nla_nest_end(skb, nla_grps);
        }

        genlmsg_end(skb, hdr);
        return 0;

nla_put_failure:
        genlmsg_cancel(skb, hdr);
        return -EMSGSIZE;
}

static int ctrl_fill_mcgrp_info(const struct genl_family *family,
                                const struct genl_multicast_group *grp,
                                int grp_id, u32 portid, u32 seq, u32 flags,
                                struct sk_buff *skb, u8 cmd)
{
        void *hdr;
        struct nlattr *nla_grps;
        struct nlattr *nest;

        hdr = genlmsg_put(skb, portid, seq, &genl_ctrl, flags, cmd);
        if (hdr == NULL)
                return -1;

        if (nla_put_string(skb, CTRL_ATTR_FAMILY_NAME, family->name) ||
            nla_put_u16(skb, CTRL_ATTR_FAMILY_ID, family->id))
                goto nla_put_failure;

        nla_grps = nla_nest_start_noflag(skb, CTRL_ATTR_MCAST_GROUPS);
        if (nla_grps == NULL)
                goto nla_put_failure;

        nest = nla_nest_start_noflag(skb, 1);
        if (nest == NULL)
                goto nla_put_failure;

        if (nla_put_u32(skb, CTRL_ATTR_MCAST_GRP_ID, grp_id) ||
            nla_put_string(skb, CTRL_ATTR_MCAST_GRP_NAME,
                           grp->name))
                goto nla_put_failure;

        nla_nest_end(skb, nest);
        nla_nest_end(skb, nla_grps);

        genlmsg_end(skb, hdr);
        return 0;

nla_put_failure:
        genlmsg_cancel(skb, hdr);
        return -EMSGSIZE;
}

static int ctrl_dumpfamily(struct sk_buff *skb, struct netlink_callback *cb)
{
        int n = 0;
        struct genl_family *rt;
        struct net *net = sock_net(skb->sk);
        int fams_to_skip = cb->args[0];
        unsigned int id;

        idr_for_each_entry(&genl_fam_idr, rt, id) {
                if (!rt->netnsok && !net_eq(net, &init_net))
                        continue;

                if (n++ < fams_to_skip)
                        continue;

                if (ctrl_fill_info(rt, NETLINK_CB(cb->skb).portid,
                                   cb->nlh->nlmsg_seq, NLM_F_MULTI,
                                   skb, CTRL_CMD_NEWFAMILY) < 0) {
                        n--;
                        break;
                }
        }

        cb->args[0] = n;
        return skb->len;
}

static struct sk_buff *ctrl_build_family_msg(const struct genl_family *family,
                                             u32 portid, int seq, u8 cmd)
{
        struct sk_buff *skb;
        int err;

        skb = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
        if (skb == NULL)
                return ERR_PTR(-ENOBUFS);

        err = ctrl_fill_info(family, portid, seq, 0, skb, cmd);
        if (err < 0) {
                nlmsg_free(skb);
                return ERR_PTR(err);
        }

        return skb;
}

static struct sk_buff *
ctrl_build_mcgrp_msg(const struct genl_family *family,
                     const struct genl_multicast_group *grp,
                     int grp_id, u32 portid, int seq, u8 cmd)
{
        struct sk_buff *skb;
        int err;

        skb = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
        if (skb == NULL)
                return ERR_PTR(-ENOBUFS);

        err = ctrl_fill_mcgrp_info(family, grp, grp_id, portid,
                                   seq, 0, skb, cmd);
        if (err < 0) {
                nlmsg_free(skb);
                return ERR_PTR(err);
        }

        return skb;
}

static const struct nla_policy ctrl_policy[CTRL_ATTR_MAX+1] = {
        [CTRL_ATTR_FAMILY_ID]   = { .type = NLA_U16 },
        [CTRL_ATTR_FAMILY_NAME] = { .type = NLA_NUL_STRING,
                                    .len = GENL_NAMSIZ - 1 },
};

static int ctrl_getfamily(struct sk_buff *skb, struct genl_info *info)
{
        struct sk_buff *msg;
        const struct genl_family *res = NULL;
        int err = -EINVAL;

        if (info->attrs[CTRL_ATTR_FAMILY_ID]) {
                u16 id = nla_get_u16(info->attrs[CTRL_ATTR_FAMILY_ID]);
                res = genl_family_find_byid(id);
                err = -ENOENT;
        }

        if (info->attrs[CTRL_ATTR_FAMILY_NAME]) {
                char *name;

                name = nla_data(info->attrs[CTRL_ATTR_FAMILY_NAME]);
                res = genl_family_find_byname(name);
#ifdef CONFIG_MODULES
                if (res == NULL) {
                        genl_unlock();
                        up_read(&cb_lock);
                        request_module("net-pf-%d-proto-%d-family-%s",
                                       PF_NETLINK, NETLINK_GENERIC, name);
                        down_read(&cb_lock);
                        genl_lock();
                        res = genl_family_find_byname(name);
                }
#endif
                err = -ENOENT;
        }

        if (res == NULL)
                return err;

        if (!res->netnsok && !net_eq(genl_info_net(info), &init_net)) {
                /* family doesn't exist here */
                return -ENOENT;
        }

        msg = ctrl_build_family_msg(res, info->snd_portid, info->snd_seq,
                                    CTRL_CMD_NEWFAMILY);
        if (IS_ERR(msg))
                return PTR_ERR(msg);

        return genlmsg_reply(msg, info);
}

static int genl_ctrl_event(int event, const struct genl_family *family,
                           const struct genl_multicast_group *grp,
                           int grp_id)
{
        struct sk_buff *msg;

        /* genl is still initialising */
        if (!init_net.genl_sock)
                return 0;

        switch (event) {
        case CTRL_CMD_NEWFAMILY:
        case CTRL_CMD_DELFAMILY:
                WARN_ON(grp);
                msg = ctrl_build_family_msg(family, 0, 0, event);
                break;
        case CTRL_CMD_NEWMCAST_GRP:
        case CTRL_CMD_DELMCAST_GRP:
                BUG_ON(!grp);
                msg = ctrl_build_mcgrp_msg(family, grp, grp_id, 0, 0, event);
                break;
        default:
                return -EINVAL;
        }

        if (IS_ERR(msg))
                return PTR_ERR(msg);

        if (!family->netnsok) {
                genlmsg_multicast_netns(&genl_ctrl, &init_net, msg, 0,
                                        0, GFP_KERNEL);
        } else {
                rcu_read_lock();
                genlmsg_multicast_allns(&genl_ctrl, msg, 0,
                                        0, GFP_ATOMIC);
                rcu_read_unlock();
        }

        return 0;
}

static const struct genl_ops genl_ctrl_ops[] = {
        {
                .cmd            = CTRL_CMD_GETFAMILY,
                .validate = GENL_DONT_VALIDATE_STRICT | GENL_DONT_VALIDATE_DUMP,
                .doit           = ctrl_getfamily,
                .dumpit         = ctrl_dumpfamily,
        },
};

static const struct genl_multicast_group genl_ctrl_groups[] = {
        { .name = "notify", },
};

static struct genl_family genl_ctrl __ro_after_init = {
        .module = THIS_MODULE,
        .ops = genl_ctrl_ops,
        .n_ops = ARRAY_SIZE(genl_ctrl_ops),
        .mcgrps = genl_ctrl_groups,
        .n_mcgrps = ARRAY_SIZE(genl_ctrl_groups),
        .id = GENL_ID_CTRL,
        .name = "nlctrl",
        .version = 0x2,
        .maxattr = CTRL_ATTR_MAX,
        .policy = ctrl_policy,
        .netnsok = true,
};

static int genl_bind(struct net *net, int group)
{
        struct genl_family *f;
        int err = -ENOENT;
        unsigned int id;

        down_read(&cb_lock);

        idr_for_each_entry(&genl_fam_idr, f, id) {

                if (group >= f->mcgrp_offset &&
                    group < f->mcgrp_offset + f->n_mcgrps) {
                        int fam_grp = group - f->mcgrp_offset;

                        if (!f->netnsok && net != &init_net)
                                err = -ENOENT;
                        else if (f->mcast_bind)
                                err = f->mcast_bind(net, fam_grp);
                        else
                                err = 0;
                        break;
                }
        }
        up_read(&cb_lock);

        return err;
}

static void genl_unbind(struct net *net, int group)
{
        struct genl_family *f;
        unsigned int id;

        down_read(&cb_lock);

        idr_for_each_entry(&genl_fam_idr, f, id) {
                if (group >= f->mcgrp_offset &&
                    group < f->mcgrp_offset + f->n_mcgrps) {
                        int fam_grp = group - f->mcgrp_offset;

                        if (f->mcast_unbind)
                                f->mcast_unbind(net, fam_grp);
                        break;
                }
        }
        up_read(&cb_lock);
}

static int __net_init genl_pernet_init(struct net *net)
{
        struct netlink_kernel_cfg cfg = {
                .input          = genl_rcv,
                .flags          = NL_CFG_F_NONROOT_RECV,
                .bind           = genl_bind,
                .unbind         = genl_unbind,
        };

        /* we'll bump the group number right afterwards */
        net->genl_sock = netlink_kernel_create(net, NETLINK_GENERIC, &cfg);

        if (!net->genl_sock && net_eq(net, &init_net))
                panic("GENL: Cannot initialize generic netlink\n");

        if (!net->genl_sock)
                return -ENOMEM;

        return 0;
}

static void __net_exit genl_pernet_exit(struct net *net)
{
        netlink_kernel_release(net->genl_sock);
        net->genl_sock = NULL;
}

static struct pernet_operations genl_pernet_ops = {
        .init = genl_pernet_init,
        .exit = genl_pernet_exit,
};

static int __init genl_init(void)
{
        int err;

        err = genl_register_family(&genl_ctrl);
        if (err < 0)
                goto problem;

        err = register_pernet_subsys(&genl_pernet_ops);
        if (err)
                goto problem;

        return 0;

problem:
        panic("GENL: Cannot register controller: %d\n", err);
}

subsys_initcall(genl_init);

/**
 * genl_family_attrbuf - return family's attrbuf
 * @family: the family
 *
 * Return the family's attrbuf, while validating that it's
 * actually valid to access it.
 *
 * You cannot use this function with a family that has parallel_ops
 * and you can only use it within (pre/post) doit/dumpit callbacks.
 */
struct nlattr **genl_family_attrbuf(const struct genl_family *family)
{
        if (!WARN_ON(family->parallel_ops))
                lockdep_assert_held(&genl_mutex);

        return family->attrbuf;
}
EXPORT_SYMBOL(genl_family_attrbuf);

static int genlmsg_mcast(struct sk_buff *skb, u32 portid, unsigned long group,
                         gfp_t flags)
{
        struct sk_buff *tmp;
        struct net *net, *prev = NULL;
        bool delivered = false;
        int err;

        for_each_net_rcu(net) {
                if (prev) {
                        tmp = skb_clone(skb, flags);
                        if (!tmp) {
                                err = -ENOMEM;
                                goto error;
                        }
                        err = nlmsg_multicast(prev->genl_sock, tmp,
                                              portid, group, flags);
                        if (!err)
                                delivered = true;
                        else if (err != -ESRCH)
                                goto error;
                }

                prev = net;
        }

        err = nlmsg_multicast(prev->genl_sock, skb, portid, group, flags);
        if (!err)
                delivered = true;
        else if (err != -ESRCH)
                return err;
        return delivered ? 0 : -ESRCH;
 error:
        kfree_skb(skb);
        return err;
}

int genlmsg_multicast_allns(const struct genl_family *family,
                            struct sk_buff *skb, u32 portid,
                            unsigned int group, gfp_t flags)
{
        if (WARN_ON_ONCE(group >= family->n_mcgrps))
                return -EINVAL;
        group = family->mcgrp_offset + group;
        return genlmsg_mcast(skb, portid, group, flags);
}
EXPORT_SYMBOL(genlmsg_multicast_allns);

void genl_notify(const struct genl_family *family, struct sk_buff *skb,
                 struct genl_info *info, u32 group, gfp_t flags)
{
        struct net *net = genl_info_net(info);
        struct sock *sk = net->genl_sock;
        int report = 0;

        if (info->nlhdr)
                report = nlmsg_report(info->nlhdr);

        if (WARN_ON_ONCE(group >= family->n_mcgrps))
                return;
        group = family->mcgrp_offset + group;
        nlmsg_notify(sk, skb, info->snd_portid, group, report, flags);
}
EXPORT_SYMBOL(genl_notify);