// SPDX-License-Identifier: GPL-2.0-only
/*
 * x_tables core - Backend for {ip,ip6,arp}_tables
 *
 * Copyright (C) 2006-2006 Harald Welte <laforge@netfilter.org>
 * Copyright (C) 2006-2012 Patrick McHardy <kaber@trash.net>
 *
 * Based on existing ip_tables code which is
 *   Copyright (C) 1999 Paul `Rusty' Russell & Michael J. Neuling
 *   Copyright (C) 2000-2005 Netfilter Core Team <coreteam@netfilter.org>
 */
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/socket.h>
#include <linux/net.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#include <linux/string.h>
#include <linux/vmalloc.h>
#include <linux/mutex.h>
#include <linux/mm.h>
#include <linux/slab.h>
#include <linux/audit.h>
#include <linux/user_namespace.h>
#include <net/net_namespace.h>

#include <linux/netfilter/x_tables.h>
#include <linux/netfilter_arp.h>
#include <linux/netfilter_ipv4/ip_tables.h>
#include <linux/netfilter_ipv6/ip6_tables.h>
#include <linux/netfilter_arp/arp_tables.h>

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>");
MODULE_DESCRIPTION("{ip,ip6,arp,eb}_tables backend module");

#define XT_PCPU_BLOCK_SIZE 4096
#define XT_MAX_TABLE_SIZE       (512 * 1024 * 1024)

struct compat_delta {
        unsigned int offset; /* offset in kernel */
        int delta; /* delta in 32bit user land */
};

struct xt_af {
        struct mutex mutex;
        struct list_head match;
        struct list_head target;
#ifdef CONFIG_COMPAT
        struct mutex compat_mutex;
        struct compat_delta *compat_tab;
        unsigned int number; /* number of slots in compat_tab[] */
        unsigned int cur; /* number of used slots in compat_tab[] */
#endif
};

static struct xt_af *xt;

static const char *const xt_prefix[NFPROTO_NUMPROTO] = {
        [NFPROTO_UNSPEC] = "x",
        [NFPROTO_IPV4]   = "ip",
        [NFPROTO_ARP]    = "arp",
        [NFPROTO_BRIDGE] = "eb",
        [NFPROTO_IPV6]   = "ip6",
};

/* Registration hooks for targets. */
int xt_register_target(struct xt_target *target)
{
        u_int8_t af = target->family;

        mutex_lock(&xt[af].mutex);
        list_add(&target->list, &xt[af].target);
        mutex_unlock(&xt[af].mutex);
        return 0;
}
EXPORT_SYMBOL(xt_register_target);

void
xt_unregister_target(struct xt_target *target)
{
        u_int8_t af = target->family;

        mutex_lock(&xt[af].mutex);
        list_del(&target->list);
        mutex_unlock(&xt[af].mutex);
}
EXPORT_SYMBOL(xt_unregister_target);

int
xt_register_targets(struct xt_target *target, unsigned int n)
{
        unsigned int i;
        int err = 0;

        for (i = 0; i < n; i++) {
                err = xt_register_target(&target[i]);
                if (err)
                        goto err;
        }
        return err;

err:
        if (i > 0)
                xt_unregister_targets(target, i);
        return err;
}
EXPORT_SYMBOL(xt_register_targets);

void
xt_unregister_targets(struct xt_target *target, unsigned int n)
{
        while (n-- > 0)
                xt_unregister_target(&target[n]);
}
EXPORT_SYMBOL(xt_unregister_targets);

int xt_register_match(struct xt_match *match)
{
        u_int8_t af = match->family;

        mutex_lock(&xt[af].mutex);
        list_add(&match->list, &xt[af].match);
        mutex_unlock(&xt[af].mutex);
        return 0;
}
EXPORT_SYMBOL(xt_register_match);

void
xt_unregister_match(struct xt_match *match)
{
        u_int8_t af = match->family;

        mutex_lock(&xt[af].mutex);
        list_del(&match->list);
        mutex_unlock(&xt[af].mutex);
}
EXPORT_SYMBOL(xt_unregister_match);

int
xt_register_matches(struct xt_match *match, unsigned int n)
{
        unsigned int i;
        int err = 0;

        for (i = 0; i < n; i++) {
                err = xt_register_match(&match[i]);
                if (err)
                        goto err;
        }
        return err;

err:
        if (i > 0)
                xt_unregister_matches(match, i);
        return err;
}
EXPORT_SYMBOL(xt_register_matches);

void
xt_unregister_matches(struct xt_match *match, unsigned int n)
{
        while (n-- > 0)
                xt_unregister_match(&match[n]);
}
EXPORT_SYMBOL(xt_unregister_matches);


/*
 * These are weird, but module loading must not be done with mutex
 * held (since they will register), and we have to have a single
 * function to use.
 */

/* Find match, grabs ref.  Returns ERR_PTR() on error. */
struct xt_match *xt_find_match(u8 af, const char *name, u8 revision)
{
        struct xt_match *m;
        int err = -ENOENT;

        if (strnlen(name, XT_EXTENSION_MAXNAMELEN) == XT_EXTENSION_MAXNAMELEN)
                return ERR_PTR(-EINVAL);

        mutex_lock(&xt[af].mutex);
        list_for_each_entry(m, &xt[af].match, list) {
                if (strcmp(m->name, name) == 0) {
                        if (m->revision == revision) {
                                if (try_module_get(m->me)) {
                                        mutex_unlock(&xt[af].mutex);
                                        return m;
                                }
                        } else
                                err = -EPROTOTYPE; /* Found something. */
                }
        }
        mutex_unlock(&xt[af].mutex);

        if (af != NFPROTO_UNSPEC)
                /* Try searching again in the family-independent list */
                return xt_find_match(NFPROTO_UNSPEC, name, revision);

        return ERR_PTR(err);
}
EXPORT_SYMBOL(xt_find_match);

struct xt_match *
xt_request_find_match(uint8_t nfproto, const char *name, uint8_t revision)
{
        struct xt_match *match;

        if (strnlen(name, XT_EXTENSION_MAXNAMELEN) == XT_EXTENSION_MAXNAMELEN)
                return ERR_PTR(-EINVAL);

        match = xt_find_match(nfproto, name, revision);
        if (IS_ERR(match)) {
                request_module("%st_%s", xt_prefix[nfproto], name);
                match = xt_find_match(nfproto, name, revision);
        }

        return match;
}
EXPORT_SYMBOL_GPL(xt_request_find_match);

/* Find target, grabs ref.  Returns ERR_PTR() on error. */
static struct xt_target *xt_find_target(u8 af, const char *name, u8 revision)
{
        struct xt_target *t;
        int err = -ENOENT;

        if (strnlen(name, XT_EXTENSION_MAXNAMELEN) == XT_EXTENSION_MAXNAMELEN)
                return ERR_PTR(-EINVAL);

        mutex_lock(&xt[af].mutex);
        list_for_each_entry(t, &xt[af].target, list) {
                if (strcmp(t->name, name) == 0) {
                        if (t->revision == revision) {
                                if (try_module_get(t->me)) {
                                        mutex_unlock(&xt[af].mutex);
                                        return t;
                                }
                        } else
                                err = -EPROTOTYPE; /* Found something. */
                }
        }
        mutex_unlock(&xt[af].mutex);

        if (af != NFPROTO_UNSPEC)
                /* Try searching again in the family-independent list */
                return xt_find_target(NFPROTO_UNSPEC, name, revision);

        return ERR_PTR(err);
}

struct xt_target *xt_request_find_target(u8 af, const char *name, u8 revision)
{
        struct xt_target *target;

        if (strnlen(name, XT_EXTENSION_MAXNAMELEN) == XT_EXTENSION_MAXNAMELEN)
                return ERR_PTR(-EINVAL);

        target = xt_find_target(af, name, revision);
        if (IS_ERR(target)) {
                request_module("%st_%s", xt_prefix[af], name);
                target = xt_find_target(af, name, revision);
        }

        return target;
}
EXPORT_SYMBOL_GPL(xt_request_find_target);


static int xt_obj_to_user(u16 __user *psize, u16 size,
                          void __user *pname, const char *name,
                          u8 __user *prev, u8 rev)
{
        if (put_user(size, psize))
                return -EFAULT;
        if (copy_to_user(pname, name, strlen(name) + 1))
                return -EFAULT;
        if (put_user(rev, prev))
                return -EFAULT;

        return 0;
}

#define XT_OBJ_TO_USER(U, K, TYPE, C_SIZE)                              \
        xt_obj_to_user(&U->u.TYPE##_size, C_SIZE ? : K->u.TYPE##_size,  \
                       U->u.user.name, K->u.kernel.TYPE->name,          \
                       &U->u.user.revision, K->u.kernel.TYPE->revision)

int xt_data_to_user(void __user *dst, const void *src,
                    int usersize, int size, int aligned_size)
{
        usersize = usersize ? : size;
        if (copy_to_user(dst, src, usersize))
                return -EFAULT;
        if (usersize != aligned_size &&
            clear_user(dst + usersize, aligned_size - usersize))
                return -EFAULT;

        return 0;
}
EXPORT_SYMBOL_GPL(xt_data_to_user);

#define XT_DATA_TO_USER(U, K, TYPE)                                     \
        xt_data_to_user(U->data, K->data,                               \
                        K->u.kernel.TYPE->usersize,                     \
                        K->u.kernel.TYPE->TYPE##size,                   \
                        XT_ALIGN(K->u.kernel.TYPE->TYPE##size))

int xt_match_to_user(const struct xt_entry_match *m,
                     struct xt_entry_match __user *u)
{
        return XT_OBJ_TO_USER(u, m, match, 0) ||
               XT_DATA_TO_USER(u, m, match);
}
EXPORT_SYMBOL_GPL(xt_match_to_user);

int xt_target_to_user(const struct xt_entry_target *t,
                      struct xt_entry_target __user *u)
{
        return XT_OBJ_TO_USER(u, t, target, 0) ||
               XT_DATA_TO_USER(u, t, target);
}
EXPORT_SYMBOL_GPL(xt_target_to_user);

static int match_revfn(u8 af, const char *name, u8 revision, int *bestp)
{
        const struct xt_match *m;
        int have_rev = 0;

        mutex_lock(&xt[af].mutex);
        list_for_each_entry(m, &xt[af].match, list) {
                if (strcmp(m->name, name) == 0) {
                        if (m->revision > *bestp)
                                *bestp = m->revision;
                        if (m->revision == revision)
                                have_rev = 1;
                }
        }
        mutex_unlock(&xt[af].mutex);

        if (af != NFPROTO_UNSPEC && !have_rev)
                return match_revfn(NFPROTO_UNSPEC, name, revision, bestp);

        return have_rev;
}

static int target_revfn(u8 af, const char *name, u8 revision, int *bestp)
{
        const struct xt_target *t;
        int have_rev = 0;

        mutex_lock(&xt[af].mutex);
        list_for_each_entry(t, &xt[af].target, list) {
                if (strcmp(t->name, name) == 0) {
                        if (t->revision > *bestp)
                                *bestp = t->revision;
                        if (t->revision == revision)
                                have_rev = 1;
                }
        }
        mutex_unlock(&xt[af].mutex);

        if (af != NFPROTO_UNSPEC && !have_rev)
                return target_revfn(NFPROTO_UNSPEC, name, revision, bestp);

        return have_rev;
}

/* Returns true or false (if no such extension at all) */
int xt_find_revision(u8 af, const char *name, u8 revision, int target,
                     int *err)
{
        int have_rev, best = -1;

        if (target == 1)
                have_rev = target_revfn(af, name, revision, &best);
        else
                have_rev = match_revfn(af, name, revision, &best);

        /* Nothing at all?  Return 0 to try loading module. */
        if (best == -1) {
                *err = -ENOENT;
                return 0;
        }

        *err = best;
        if (!have_rev)
                *err = -EPROTONOSUPPORT;
        return 1;
}
EXPORT_SYMBOL_GPL(xt_find_revision);

static char *
textify_hooks(char *buf, size_t size, unsigned int mask, uint8_t nfproto)
{
        static const char *const inetbr_names[] = {
                "PREROUTING", "INPUT", "FORWARD",
                "OUTPUT", "POSTROUTING", "BROUTING",
        };
        static const char *const arp_names[] = {
                "INPUT", "FORWARD", "OUTPUT",
        };
        const char *const *names;
        unsigned int i, max;
        char *p = buf;
        bool np = false;
        int res;

        names = (nfproto == NFPROTO_ARP) ? arp_names : inetbr_names;
        max   = (nfproto == NFPROTO_ARP) ? ARRAY_SIZE(arp_names) :
                                           ARRAY_SIZE(inetbr_names);
        *p = '\0';
        for (i = 0; i < max; ++i) {
                if (!(mask & (1 << i)))
                        continue;
                res = snprintf(p, size, "%s%s", np ? "/" : "", names[i]);
                if (res > 0) {
                        size -= res;
                        p += res;
                }
                np = true;
        }

        return buf;
}

/**
 * xt_check_proc_name - check that name is suitable for /proc file creation
 *
 * @name: file name candidate
 * @size: length of buffer
 *
 * some x_tables modules wish to create a file in /proc.
 * This function makes sure that the name is suitable for this
 * purpose, it checks that name is NUL terminated and isn't a 'special'
 * name, like "..".
 *
 * returns negative number on error or 0 if name is useable.
 */
int xt_check_proc_name(const char *name, unsigned int size)
{
        if (name[0] == '\0')
                return -EINVAL;

        if (strnlen(name, size) == size)
                return -ENAMETOOLONG;

        if (strcmp(name, ".") == 0 ||
            strcmp(name, "..") == 0 ||
            strchr(name, '/'))
                return -EINVAL;

        return 0;
}
EXPORT_SYMBOL(xt_check_proc_name);

int xt_check_match(struct xt_mtchk_param *par,
                   unsigned int size, u16 proto, bool inv_proto)
{
        int ret;

        if (XT_ALIGN(par->match->matchsize) != size &&
            par->match->matchsize != -1) {
                /*
                 * ebt_among is exempt from centralized matchsize checking
                 * because it uses a dynamic-size data set.
                 */
                pr_err_ratelimited("%s_tables: %s.%u match: invalid size %u (kernel) != (user) %u\n",
                                   xt_prefix[par->family], par->match->name,
                                   par->match->revision,
                                   XT_ALIGN(par->match->matchsize), size);
                return -EINVAL;
        }
        if (par->match->table != NULL &&
            strcmp(par->match->table, par->table) != 0) {
                pr_info_ratelimited("%s_tables: %s match: only valid in %s table, not %s\n",
                                    xt_prefix[par->family], par->match->name,
                                    par->match->table, par->table);
                return -EINVAL;
        }
        if (par->match->hooks && (par->hook_mask & ~par->match->hooks) != 0) {
                char used[64], allow[64];

                pr_info_ratelimited("%s_tables: %s match: used from hooks %s, but only valid from %s\n",
                                    xt_prefix[par->family], par->match->name,
                                    textify_hooks(used, sizeof(used),
                                                  par->hook_mask, par->family),
                                    textify_hooks(allow, sizeof(allow),
                                                  par->match->hooks,
                                                  par->family));
                return -EINVAL;
        }
        if (par->match->proto && (par->match->proto != proto || inv_proto)) {
                pr_info_ratelimited("%s_tables: %s match: only valid for protocol %u\n",
                                    xt_prefix[par->family], par->match->name,
                                    par->match->proto);
                return -EINVAL;
        }
        if (par->match->checkentry != NULL) {
                ret = par->match->checkentry(par);
                if (ret < 0)
                        return ret;
                else if (ret > 0)
                        /* Flag up potential errors. */
                        return -EIO;
        }
        return 0;
}
EXPORT_SYMBOL_GPL(xt_check_match);

/** xt_check_entry_match - check that matches end before start of target
 *
 * @match: beginning of xt_entry_match
 * @target: beginning of this rules target (alleged end of matches)
 * @alignment: alignment requirement of match structures
 *
 * Validates that all matches add up to the beginning of the target,
 * and that each match covers at least the base structure size.
 *
 * Return: 0 on success, negative errno on failure.
 */
static int xt_check_entry_match(const char *match, const char *target,
                                const size_t alignment)
{
        const struct xt_entry_match *pos;
        int length = target - match;

        if (length == 0) /* no matches */
                return 0;

        pos = (struct xt_entry_match *)match;
        do {
                if ((unsigned long)pos % alignment)
                        return -EINVAL;

                if (length < (int)sizeof(struct xt_entry_match))
                        return -EINVAL;

                if (pos->u.match_size < sizeof(struct xt_entry_match))
                        return -EINVAL;

                if (pos->u.match_size > length)
                        return -EINVAL;

                length -= pos->u.match_size;
                pos = ((void *)((char *)(pos) + (pos)->u.match_size));
        } while (length > 0);

        return 0;
}

/** xt_check_table_hooks - check hook entry points are sane
 *
 * @info xt_table_info to check
 * @valid_hooks - hook entry points that we can enter from
 *
 * Validates that the hook entry and underflows points are set up.
 *
 * Return: 0 on success, negative errno on failure.
 */
int xt_check_table_hooks(const struct xt_table_info *info, unsigned int valid_hooks)
{
        const char *err = "unsorted underflow";
        unsigned int i, max_uflow, max_entry;
        bool check_hooks = false;

        BUILD_BUG_ON(ARRAY_SIZE(info->hook_entry) != ARRAY_SIZE(info->underflow));

        max_entry = 0;
        max_uflow = 0;

        for (i = 0; i < ARRAY_SIZE(info->hook_entry); i++) {
                if (!(valid_hooks & (1 << i)))
                        continue;

                if (info->hook_entry[i] == 0xFFFFFFFF)
                        return -EINVAL;
                if (info->underflow[i] == 0xFFFFFFFF)
                        return -EINVAL;

                if (check_hooks) {
                        if (max_uflow > info->underflow[i])
                                goto error;

                        if (max_uflow == info->underflow[i]) {
                                err = "duplicate underflow";
                                goto error;
                        }
                        if (max_entry > info->hook_entry[i]) {
                                err = "unsorted entry";
                                goto error;
                        }
                        if (max_entry == info->hook_entry[i]) {
                                err = "duplicate entry";
                                goto error;
                        }
                }
                max_entry = info->hook_entry[i];
                max_uflow = info->underflow[i];
                check_hooks = true;
        }

        return 0;
error:
        pr_err_ratelimited("%s at hook %d\n", err, i);
        return -EINVAL;
}
EXPORT_SYMBOL(xt_check_table_hooks);

static bool verdict_ok(int verdict)
{
        if (verdict > 0)
                return true;

        if (verdict < 0) {
                int v = -verdict - 1;

                if (verdict == XT_RETURN)
                        return true;

                switch (v) {
                case NF_ACCEPT: return true;
                case NF_DROP: return true;
                case NF_QUEUE: return true;
                default:
                        break;
                }

                return false;
        }

        return false;
}

static bool error_tg_ok(unsigned int usersize, unsigned int kernsize,
                        const char *msg, unsigned int msglen)
{
        return usersize == kernsize && strnlen(msg, msglen) < msglen;
}

#ifdef CONFIG_COMPAT
int xt_compat_add_offset(u_int8_t af, unsigned int offset, int delta)
{
        struct xt_af *xp = &xt[af];

        WARN_ON(!mutex_is_locked(&xt[af].compat_mutex));

        if (WARN_ON(!xp->compat_tab))
                return -ENOMEM;

        if (xp->cur >= xp->number)
                return -EINVAL;

        if (xp->cur)
                delta += xp->compat_tab[xp->cur - 1].delta;
        xp->compat_tab[xp->cur].offset = offset;
        xp->compat_tab[xp->cur].delta = delta;
        xp->cur++;
        return 0;
}
EXPORT_SYMBOL_GPL(xt_compat_add_offset);

void xt_compat_flush_offsets(u_int8_t af)
{
        WARN_ON(!mutex_is_locked(&xt[af].compat_mutex));

        if (xt[af].compat_tab) {
                vfree(xt[af].compat_tab);
                xt[af].compat_tab = NULL;
                xt[af].number = 0;
                xt[af].cur = 0;
        }
}
EXPORT_SYMBOL_GPL(xt_compat_flush_offsets);

int xt_compat_calc_jump(u_int8_t af, unsigned int offset)
{
        struct compat_delta *tmp = xt[af].compat_tab;
        int mid, left = 0, right = xt[af].cur - 1;

        while (left <= right) {
                mid = (left + right) >> 1;
                if (offset > tmp[mid].offset)
                        left = mid + 1;
                else if (offset < tmp[mid].offset)
                        right = mid - 1;
                else
                        return mid ? tmp[mid - 1].delta : 0;
        }
        return left ? tmp[left - 1].delta : 0;
}
EXPORT_SYMBOL_GPL(xt_compat_calc_jump);

int xt_compat_init_offsets(u8 af, unsigned int number)
{
        size_t mem;

        WARN_ON(!mutex_is_locked(&xt[af].compat_mutex));

        if (!number || number > (INT_MAX / sizeof(struct compat_delta)))
                return -EINVAL;

        if (WARN_ON(xt[af].compat_tab))
                return -EINVAL;

        mem = sizeof(struct compat_delta) * number;
        if (mem > XT_MAX_TABLE_SIZE)
                return -ENOMEM;

        xt[af].compat_tab = vmalloc(mem);
        if (!xt[af].compat_tab)
                return -ENOMEM;

        xt[af].number = number;
        xt[af].cur = 0;

        return 0;
}
EXPORT_SYMBOL(xt_compat_init_offsets);

int xt_compat_match_offset(const struct xt_match *match)
{
        u_int16_t csize = match->compatsize ? : match->matchsize;
        return XT_ALIGN(match->matchsize) - COMPAT_XT_ALIGN(csize);
}
EXPORT_SYMBOL_GPL(xt_compat_match_offset);

void xt_compat_match_from_user(struct xt_entry_match *m, void **dstptr,
                               unsigned int *size)
{
        const struct xt_match *match = m->u.kernel.match;
        struct compat_xt_entry_match *cm = (struct compat_xt_entry_match *)m;
        int off = xt_compat_match_offset(match);
        u_int16_t msize = cm->u.user.match_size;
        char name[sizeof(m->u.user.name)];

        m = *dstptr;
        memcpy(m, cm, sizeof(*cm));
        if (match->compat_from_user)
                match->compat_from_user(m->data, cm->data);
        else
                memcpy(m->data, cm->data, msize - sizeof(*cm));

        msize += off;
        m->u.user.match_size = msize;
        strlcpy(name, match->name, sizeof(name));
        module_put(match->me);
        strncpy(m->u.user.name, name, sizeof(m->u.user.name));

        *size += off;
        *dstptr += msize;
}
EXPORT_SYMBOL_GPL(xt_compat_match_from_user);

#define COMPAT_XT_DATA_TO_USER(U, K, TYPE, C_SIZE)                      \
        xt_data_to_user(U->data, K->data,                               \
                        K->u.kernel.TYPE->usersize,                     \
                        C_SIZE,                                         \
                        COMPAT_XT_ALIGN(C_SIZE))

int xt_compat_match_to_user(const struct xt_entry_match *m,
                            void __user **dstptr, unsigned int *size)
{
        const struct xt_match *match = m->u.kernel.match;
        struct compat_xt_entry_match __user *cm = *dstptr;
        int off = xt_compat_match_offset(match);
        u_int16_t msize = m->u.user.match_size - off;

        if (XT_OBJ_TO_USER(cm, m, match, msize))
                return -EFAULT;

        if (match->compat_to_user) {
                if (match->compat_to_user((void __user *)cm->data, m->data))
                        return -EFAULT;
        } else {
                if (COMPAT_XT_DATA_TO_USER(cm, m, match, msize - sizeof(*cm)))
                        return -EFAULT;
        }

        *size -= off;
        *dstptr += msize;
        return 0;
}
EXPORT_SYMBOL_GPL(xt_compat_match_to_user);

/* non-compat version may have padding after verdict */
struct compat_xt_standard_target {
        struct compat_xt_entry_target t;
        compat_uint_t verdict;
};

struct compat_xt_error_target {
        struct compat_xt_entry_target t;
        char errorname[XT_FUNCTION_MAXNAMELEN];
};

int xt_compat_check_entry_offsets(const void *base, const char *elems,
                                  unsigned int target_offset,
                                  unsigned int next_offset)
{
        long size_of_base_struct = elems - (const char *)base;
        const struct compat_xt_entry_target *t;
        const char *e = base;

        if (target_offset < size_of_base_struct)
                return -EINVAL;

        if (target_offset + sizeof(*t) > next_offset)
                return -EINVAL;

        t = (void *)(e + target_offset);
        if (t->u.target_size < sizeof(*t))
                return -EINVAL;

        if (target_offset + t->u.target_size > next_offset)
                return -EINVAL;

        if (strcmp(t->u.user.name, XT_STANDARD_TARGET) == 0) {
                const struct compat_xt_standard_target *st = (const void *)t;

                if (COMPAT_XT_ALIGN(target_offset + sizeof(*st)) != next_offset)
                        return -EINVAL;

                if (!verdict_ok(st->verdict))
                        return -EINVAL;
        } else if (strcmp(t->u.user.name, XT_ERROR_TARGET) == 0) {
                const struct compat_xt_error_target *et = (const void *)t;

                if (!error_tg_ok(t->u.target_size, sizeof(*et),
                                 et->errorname, sizeof(et->errorname)))
                        return -EINVAL;
        }

        /* compat_xt_entry match has less strict alignment requirements,
         * otherwise they are identical.  In case of padding differences
         * we need to add compat version of xt_check_entry_match.
         */
        BUILD_BUG_ON(sizeof(struct compat_xt_entry_match) != sizeof(struct xt_entry_match));

        return xt_check_entry_match(elems, base + target_offset,
                                    __alignof__(struct compat_xt_entry_match));
}
EXPORT_SYMBOL(xt_compat_check_entry_offsets);
#endif /* CONFIG_COMPAT */

/**
 * xt_check_entry_offsets - validate arp/ip/ip6t_entry
 *
 * @base: pointer to arp/ip/ip6t_entry
 * @elems: pointer to first xt_entry_match, i.e. ip(6)t_entry->elems
 * @target_offset: the arp/ip/ip6_t->target_offset
 * @next_offset: the arp/ip/ip6_t->next_offset
 *
 * validates that target_offset and next_offset are sane and that all
 * match sizes (if any) align with the target offset.
 *
 * This function does not validate the targets or matches themselves, it
 * only tests that all the offsets and sizes are correct, that all
 * match structures are aligned, and that the last structure ends where
 * the target structure begins.
 *
 * Also see xt_compat_check_entry_offsets for CONFIG_COMPAT version.
 *
 * The arp/ip/ip6t_entry structure @base must have passed following tests:
 * - it must point to a valid memory location
 * - base to base + next_offset must be accessible, i.e. not exceed allocated
 *   length.
 *
 * A well-formed entry looks like this:
 *
 * ip(6)t_entry   match [mtdata]  match [mtdata] target [tgdata] ip(6)t_entry
 * e->elems[]-----'                              |               |
 *                matchsize                      |               |
 *                                matchsize      |               |
 *                                               |               |
 * target_offset---------------------------------'               |
 * next_offset---------------------------------------------------'
 *
 * elems[]: flexible array member at end of ip(6)/arpt_entry struct.
 *          This is where matches (if any) and the target reside.
 * target_offset: beginning of target.
 * next_offset: start of the next rule; also: size of this rule.
 * Since targets have a minimum size, target_offset + minlen <= next_offset.
 *
 * Every match stores its size, sum of sizes must not exceed target_offset.
 *
 * Return: 0 on success, negative errno on failure.
 */
int xt_check_entry_offsets(const void *base,
                           const char *elems,
                           unsigned int target_offset,
                           unsigned int next_offset)
{
        long size_of_base_struct = elems - (const char *)base;
        const struct xt_entry_target *t;
        const char *e = base;

        /* target start is within the ip/ip6/arpt_entry struct */
        if (target_offset < size_of_base_struct)
                return -EINVAL;

        if (target_offset + sizeof(*t) > next_offset)
                return -EINVAL;

        t = (void *)(e + target_offset);
        if (t->u.target_size < sizeof(*t))
                return -EINVAL;

        if (target_offset + t->u.target_size > next_offset)
                return -EINVAL;

        if (strcmp(t->u.user.name, XT_STANDARD_TARGET) == 0) {
                const struct xt_standard_target *st = (const void *)t;

                if (XT_ALIGN(target_offset + sizeof(*st)) != next_offset)
                        return -EINVAL;

                if (!verdict_ok(st->verdict))
                        return -EINVAL;
        } else if (strcmp(t->u.user.name, XT_ERROR_TARGET) == 0) {
                const struct xt_error_target *et = (const void *)t;

                if (!error_tg_ok(t->u.target_size, sizeof(*et),
                                 et->errorname, sizeof(et->errorname)))
                        return -EINVAL;
        }

        return xt_check_entry_match(elems, base + target_offset,
                                    __alignof__(struct xt_entry_match));
}
EXPORT_SYMBOL(xt_check_entry_offsets);

/**
 * xt_alloc_entry_offsets - allocate array to store rule head offsets
 *
 * @size: number of entries
 *
 * Return: NULL or zeroed kmalloc'd or vmalloc'd array
 */
unsigned int *xt_alloc_entry_offsets(unsigned int size)
{
        if (size > XT_MAX_TABLE_SIZE / sizeof(unsigned int))
                return NULL;

        return kvcalloc(size, sizeof(unsigned int), GFP_KERNEL);

}
EXPORT_SYMBOL(xt_alloc_entry_offsets);

/**
 * xt_find_jump_offset - check if target is a valid jump offset
 *
 * @offsets: array containing all valid rule start offsets of a rule blob
 * @target: the jump target to search for
 * @size: entries in @offset
 */
bool xt_find_jump_offset(const unsigned int *offsets,
                         unsigned int target, unsigned int size)
{
        int m, low = 0, hi = size;

        while (hi > low) {
                m = (low + hi) / 2u;

                if (offsets[m] > target)
                        hi = m;
                else if (offsets[m] < target)
                        low = m + 1;
                else
                        return true;
        }

        return false;
}
EXPORT_SYMBOL(xt_find_jump_offset);

int xt_check_target(struct xt_tgchk_param *par,
                    unsigned int size, u16 proto, bool inv_proto)
{
        int ret;

        if (XT_ALIGN(par->target->targetsize) != size) {
                pr_err_ratelimited("%s_tables: %s.%u target: invalid size %u (kernel) != (user) %u\n",
                                   xt_prefix[par->family], par->target->name,
                                   par->target->revision,
                                   XT_ALIGN(par->target->targetsize), size);
                return -EINVAL;
        }
        if (par->target->table != NULL &&
            strcmp(par->target->table, par->table) != 0) {
                pr_info_ratelimited("%s_tables: %s target: only valid in %s table, not %s\n",
                                    xt_prefix[par->family], par->target->name,
                                    par->target->table, par->table);
                return -EINVAL;
        }
        if (par->target->hooks && (par->hook_mask & ~par->target->hooks) != 0) {
                char used[64], allow[64];

                pr_info_ratelimited("%s_tables: %s target: used from hooks %s, but only usable from %s\n",
                                    xt_prefix[par->family], par->target->name,
                                    textify_hooks(used, sizeof(used),
                                                  par->hook_mask, par->family),
                                    textify_hooks(allow, sizeof(allow),
                                                  par->target->hooks,
                                                  par->family));
                return -EINVAL;
        }
        if (par->target->proto && (par->target->proto != proto || inv_proto)) {
                pr_info_ratelimited("%s_tables: %s target: only valid for protocol %u\n",
                                    xt_prefix[par->family], par->target->name,
                                    par->target->proto);
                return -EINVAL;
        }
        if (par->target->checkentry != NULL) {
                ret = par->target->checkentry(par);
                if (ret < 0)
                        return ret;
                else if (ret > 0)
                        /* Flag up potential errors. */
                        return -EIO;
        }
        return 0;
}
EXPORT_SYMBOL_GPL(xt_check_target);

/**
 * xt_copy_counters - copy counters and metadata from a sockptr_t
 *
 * @arg: src sockptr
 * @len: alleged size of userspace memory
 * @info: where to store the xt_counters_info metadata
 *
 * Copies counter meta data from @user and stores it in @info.
 *
 * vmallocs memory to hold the counters, then copies the counter data
 * from @user to the new memory and returns a pointer to it.
 *
 * If called from a compat syscall, @info gets converted automatically to the
 * 64bit representation.
 *
 * The metadata associated with the counters is stored in @info.
 *
 * Return: returns pointer that caller has to test via IS_ERR().
 * If IS_ERR is false, caller has to vfree the pointer.
 */
void *xt_copy_counters(sockptr_t arg, unsigned int len,
                       struct xt_counters_info *info)
{
        size_t offset;
        void *mem;
        u64 size;

#ifdef CONFIG_COMPAT
        if (in_compat_syscall()) {
                /* structures only differ in size due to alignment */
                struct compat_xt_counters_info compat_tmp;

                if (len <= sizeof(compat_tmp))
                        return ERR_PTR(-EINVAL);

                len -= sizeof(compat_tmp);
                if (copy_from_sockptr(&compat_tmp, arg, sizeof(compat_tmp)) != 0)
                        return ERR_PTR(-EFAULT);

                memcpy(info->name, compat_tmp.name, sizeof(info->name) - 1);
                info->num_counters = compat_tmp.num_counters;
                offset = sizeof(compat_tmp);
        } else
#endif
        {
                if (len <= sizeof(*info))
                        return ERR_PTR(-EINVAL);

                len -= sizeof(*info);
                if (copy_from_sockptr(info, arg, sizeof(*info)) != 0)
                        return ERR_PTR(-EFAULT);

                offset = sizeof(*info);
        }
        info->name[sizeof(info->name) - 1] = '\0';

        size = sizeof(struct xt_counters);
        size *= info->num_counters;

        if (size != (u64)len)
                return ERR_PTR(-EINVAL);

        mem = vmalloc(len);
        if (!mem)
                return ERR_PTR(-ENOMEM);

        if (copy_from_sockptr_offset(mem, arg, offset, len) == 0)
                return mem;

        vfree(mem);
        return ERR_PTR(-EFAULT);
}
EXPORT_SYMBOL_GPL(xt_copy_counters);

#ifdef CONFIG_COMPAT
int xt_compat_target_offset(const struct xt_target *target)
{
        u_int16_t csize = target->compatsize ? : target->targetsize;
        return XT_ALIGN(target->targetsize) - COMPAT_XT_ALIGN(csize);
}
EXPORT_SYMBOL_GPL(xt_compat_target_offset);

void xt_compat_target_from_user(struct xt_entry_target *t, void **dstptr,
                                unsigned int *size)
{
        const struct xt_target *target = t->u.kernel.target;
        struct compat_xt_entry_target *ct = (struct compat_xt_entry_target *)t;
        int off = xt_compat_target_offset(target);
        u_int16_t tsize = ct->u.user.target_size;
        char name[sizeof(t->u.user.name)];

        t = *dstptr;
        memcpy(t, ct, sizeof(*ct));
        if (target->compat_from_user)
                target->compat_from_user(t->data, ct->data);
        else
                memcpy(t->data, ct->data, tsize - sizeof(*ct));

        tsize += off;
        t->u.user.target_size = tsize;
        strlcpy(name, target->name, sizeof(name));
        module_put(target->me);
        strncpy(t->u.user.name, name, sizeof(t->u.user.name));

        *size += off;
        *dstptr += tsize;
}
EXPORT_SYMBOL_GPL(xt_compat_target_from_user);

int xt_compat_target_to_user(const struct xt_entry_target *t,
                             void __user **dstptr, unsigned int *size)
{
        const struct xt_target *target = t->u.kernel.target;
        struct compat_xt_entry_target __user *ct = *dstptr;
        int off = xt_compat_target_offset(target);
        u_int16_t tsize = t->u.user.target_size - off;

        if (XT_OBJ_TO_USER(ct, t, target, tsize))
                return -EFAULT;

        if (target->compat_to_user) {
                if (target->compat_to_user((void __user *)ct->data, t->data))
                        return -EFAULT;
        } else {
                if (COMPAT_XT_DATA_TO_USER(ct, t, target, tsize - sizeof(*ct)))
                        return -EFAULT;
        }

        *size -= off;
        *dstptr += tsize;
        return 0;
}
EXPORT_SYMBOL_GPL(xt_compat_target_to_user);
#endif

struct xt_table_info *xt_alloc_table_info(unsigned int size)
{
        struct xt_table_info *info = NULL;
        size_t sz = sizeof(*info) + size;

        if (sz < sizeof(*info) || sz >= XT_MAX_TABLE_SIZE)
                return NULL;

        info = kvmalloc(sz, GFP_KERNEL_ACCOUNT);
        if (!info)
                return NULL;

        memset(info, 0, sizeof(*info));
        info->size = size;
        return info;
}
EXPORT_SYMBOL(xt_alloc_table_info);

void xt_free_table_info(struct xt_table_info *info)
{
        int cpu;

        if (info->jumpstack != NULL) {
                for_each_possible_cpu(cpu)
                        kvfree(info->jumpstack[cpu]);
                kvfree(info->jumpstack);
        }

        kvfree(info);
}
EXPORT_SYMBOL(xt_free_table_info);

/* Find table by name, grabs mutex & ref.  Returns ERR_PTR on error. */
struct xt_table *xt_find_table_lock(struct net *net, u_int8_t af,
                                    const char *name)
{
        struct xt_table *t, *found = NULL;

        mutex_lock(&xt[af].mutex);
        list_for_each_entry(t, &net->xt.tables[af], list)
                if (strcmp(t->name, name) == 0 && try_module_get(t->me))
                        return t;

        if (net == &init_net)
                goto out;

        /* Table doesn't exist in this netns, re-try init */
        list_for_each_entry(t, &init_net.xt.tables[af], list) {
                int err;

                if (strcmp(t->name, name))
                        continue;
                if (!try_module_get(t->me))
                        goto out;
                mutex_unlock(&xt[af].mutex);
                err = t->table_init(net);
                if (err < 0) {
                        module_put(t->me);
                        return ERR_PTR(err);
                }

                found = t;

                mutex_lock(&xt[af].mutex);
                break;
        }

        if (!found)
                goto out;

        /* and once again: */
        list_for_each_entry(t, &net->xt.tables[af], list)
                if (strcmp(t->name, name) == 0)
                        return t;

        module_put(found->me);
 out:
        mutex_unlock(&xt[af].mutex);
        return ERR_PTR(-ENOENT);
}
EXPORT_SYMBOL_GPL(xt_find_table_lock);

struct xt_table *xt_request_find_table_lock(struct net *net, u_int8_t af,
                                            const char *name)
{
        struct xt_table *t = xt_find_table_lock(net, af, name);

#ifdef CONFIG_MODULES
        if (IS_ERR(t)) {
                int err = request_module("%stable_%s", xt_prefix[af], name);
                if (err < 0)
                        return ERR_PTR(err);
                t = xt_find_table_lock(net, af, name);
        }
#endif

        return t;
}
EXPORT_SYMBOL_GPL(xt_request_find_table_lock);

void xt_table_unlock(struct xt_table *table)
{
        mutex_unlock(&xt[table->af].mutex);
}
EXPORT_SYMBOL_GPL(xt_table_unlock);

#ifdef CONFIG_COMPAT
void xt_compat_lock(u_int8_t af)
{
        mutex_lock(&xt[af].compat_mutex);
}
EXPORT_SYMBOL_GPL(xt_compat_lock);

void xt_compat_unlock(u_int8_t af)
{
        mutex_unlock(&xt[af].compat_mutex);
}
EXPORT_SYMBOL_GPL(xt_compat_unlock);
#endif

DEFINE_PER_CPU(seqcount_t, xt_recseq);
EXPORT_PER_CPU_SYMBOL_GPL(xt_recseq);

struct static_key xt_tee_enabled __read_mostly;
EXPORT_SYMBOL_GPL(xt_tee_enabled);

static int xt_jumpstack_alloc(struct xt_table_info *i)
{
        unsigned int size;
        int cpu;

        size = sizeof(void **) * nr_cpu_ids;
        if (size > PAGE_SIZE)
                i->jumpstack = kvzalloc(size, GFP_KERNEL);
        else
                i->jumpstack = kzalloc(size, GFP_KERNEL);
        if (i->jumpstack == NULL)
                return -ENOMEM;

        /* ruleset without jumps -- no stack needed */
        if (i->stacksize == 0)
                return 0;

        /* Jumpstack needs to be able to record two full callchains, one
         * from the first rule set traversal, plus one table reentrancy
         * via -j TEE without clobbering the callchain that brought us to
         * TEE target.
         *
         * This is done by allocating two jumpstacks per cpu, on reentry
         * the upper half of the stack is used.
         *
         * see the jumpstack setup in ipt_do_table() for more details.
         */
        size = sizeof(void *) * i->stacksize * 2u;
        for_each_possible_cpu(cpu) {
                i->jumpstack[cpu] = kvmalloc_node(size, GFP_KERNEL,
                        cpu_to_node(cpu));
                if (i->jumpstack[cpu] == NULL)
                        /*
                         * Freeing will be done later on by the callers. The
                         * chain is: xt_replace_table -> __do_replace ->
                         * do_replace -> xt_free_table_info.
                         */
                        return -ENOMEM;
        }

        return 0;
}

struct xt_counters *xt_counters_alloc(unsigned int counters)
{
        struct xt_counters *mem;

        if (counters == 0 || counters > INT_MAX / sizeof(*mem))
                return NULL;

        counters *= sizeof(*mem);
        if (counters > XT_MAX_TABLE_SIZE)
                return NULL;

        return vzalloc(counters);
}
EXPORT_SYMBOL(xt_counters_alloc);

struct xt_table_info *
xt_replace_table(struct xt_table *table,
              unsigned int num_counters,
              struct xt_table_info *newinfo,
              int *error)
{
        struct xt_table_info *private;
        unsigned int cpu;
        int ret;

        ret = xt_jumpstack_alloc(newinfo);
        if (ret < 0) {
                *error = ret;
                return NULL;
        }

        /* Do the substitution. */
        local_bh_disable();
        private = table->private;

        /* Check inside lock: is the old number correct? */
        if (num_counters != private->number) {
                pr_debug("num_counters != table->private->number (%u/%u)\n",
                         num_counters, private->number);
                local_bh_enable();
                *error = -EAGAIN;
                return NULL;
        }

        newinfo->initial_entries = private->initial_entries;
        /*
         * Ensure contents of newinfo are visible before assigning to
         * private.
         */
        smp_wmb();
        table->private = newinfo;

        /* make sure all cpus see new ->private value */
        smp_mb();

        /*
         * Even though table entries have now been swapped, other CPU's
         * may still be using the old entries...
         */
        local_bh_enable();

        /* ... so wait for even xt_recseq on all cpus */
        for_each_possible_cpu(cpu) {
                seqcount_t *s = &per_cpu(xt_recseq, cpu);
                u32 seq = raw_read_seqcount(s);

                if (seq & 1) {
                        do {
                                cond_resched();
                                cpu_relax();
                        } while (seq == raw_read_seqcount(s));
                }
        }

        audit_log_nfcfg(table->name, table->af, private->number,
                        !private->number ? AUDIT_XT_OP_REGISTER :
                                           AUDIT_XT_OP_REPLACE,
                        GFP_KERNEL);
        return private;
}
EXPORT_SYMBOL_GPL(xt_replace_table);

struct xt_table *xt_register_table(struct net *net,
                                   const struct xt_table *input_table,
                                   struct xt_table_info *bootstrap,
                                   struct xt_table_info *newinfo)
{
        int ret;
        struct xt_table_info *private;
        struct xt_table *t, *table;

        /* Don't add one object to multiple lists. */
        table = kmemdup(input_table, sizeof(struct xt_table), GFP_KERNEL);
        if (!table) {
                ret = -ENOMEM;
                goto out;
        }

        mutex_lock(&xt[table->af].mutex);
        /* Don't autoload: we'd eat our tail... */
        list_for_each_entry(t, &net->xt.tables[table->af], list) {
                if (strcmp(t->name, table->name) == 0) {
                        ret = -EEXIST;
                        goto unlock;
                }
        }

        /* Simplifies replace_table code. */
        table->private = bootstrap;

        if (!xt_replace_table(table, 0, newinfo, &ret))
                goto unlock;

        private = table->private;
        pr_debug("table->private->number = %u\n", private->number);

        /* save number of initial entries */
        private->initial_entries = private->number;

        list_add(&table->list, &net->xt.tables[table->af]);
        mutex_unlock(&xt[table->af].mutex);
        return table;

unlock:
        mutex_unlock(&xt[table->af].mutex);
        kfree(table);
out:
        return ERR_PTR(ret);
}
EXPORT_SYMBOL_GPL(xt_register_table);

void *xt_unregister_table(struct xt_table *table)
{
        struct xt_table_info *private;

        mutex_lock(&xt[table->af].mutex);
        private = table->private;
        list_del(&table->list);
        mutex_unlock(&xt[table->af].mutex);
        audit_log_nfcfg(table->name, table->af, private->number,
                        AUDIT_XT_OP_UNREGISTER, GFP_KERNEL);
        kfree(table);

        return private;
}
EXPORT_SYMBOL_GPL(xt_unregister_table);

#ifdef CONFIG_PROC_FS
static void *xt_table_seq_start(struct seq_file *seq, loff_t *pos)
{
        struct net *net = seq_file_net(seq);
        u_int8_t af = (unsigned long)PDE_DATA(file_inode(seq->file));

        mutex_lock(&xt[af].mutex);
        return seq_list_start(&net->xt.tables[af], *pos);
}

static void *xt_table_seq_next(struct seq_file *seq, void *v, loff_t *pos)
{
        struct net *net = seq_file_net(seq);
        u_int8_t af = (unsigned long)PDE_DATA(file_inode(seq->file));

        return seq_list_next(v, &net->xt.tables[af], pos);
}

static void xt_table_seq_stop(struct seq_file *seq, void *v)
{
        u_int8_t af = (unsigned long)PDE_DATA(file_inode(seq->file));

        mutex_unlock(&xt[af].mutex);
}

static int xt_table_seq_show(struct seq_file *seq, void *v)
{
        struct xt_table *table = list_entry(v, struct xt_table, list);

        if (*table->name)
                seq_printf(seq, "%s\n", table->name);
        return 0;
}

static const struct seq_operations xt_table_seq_ops = {
        .start  = xt_table_seq_start,
        .next   = xt_table_seq_next,
        .stop   = xt_table_seq_stop,
        .show   = xt_table_seq_show,
};

/*
 * Traverse state for ip{,6}_{tables,matches} for helping crossing
 * the multi-AF mutexes.
 */
struct nf_mttg_trav {
        struct list_head *head, *curr;
        uint8_t class;
};

enum {
        MTTG_TRAV_INIT,
        MTTG_TRAV_NFP_UNSPEC,
        MTTG_TRAV_NFP_SPEC,
        MTTG_TRAV_DONE,
};

static void *xt_mttg_seq_next(struct seq_file *seq, void *v, loff_t *ppos,
    bool is_target)
{
        static const uint8_t next_class[] = {
                [MTTG_TRAV_NFP_UNSPEC] = MTTG_TRAV_NFP_SPEC,
                [MTTG_TRAV_NFP_SPEC]   = MTTG_TRAV_DONE,
        };
        uint8_t nfproto = (unsigned long)PDE_DATA(file_inode(seq->file));
        struct nf_mttg_trav *trav = seq->private;

        if (ppos != NULL)
                ++(*ppos);

        switch (trav->class) {
        case MTTG_TRAV_INIT:
                trav->class = MTTG_TRAV_NFP_UNSPEC;
                mutex_lock(&xt[NFPROTO_UNSPEC].mutex);
                trav->head = trav->curr = is_target ?
                        &xt[NFPROTO_UNSPEC].target : &xt[NFPROTO_UNSPEC].match;
                break;
        case MTTG_TRAV_NFP_UNSPEC:
                trav->curr = trav->curr->next;
                if (trav->curr != trav->head)
                        break;
                mutex_unlock(&xt[NFPROTO_UNSPEC].mutex);
                mutex_lock(&xt[nfproto].mutex);
                trav->head = trav->curr = is_target ?
                        &xt[nfproto].target : &xt[nfproto].match;
                trav->class = next_class[trav->class];
                break;
        case MTTG_TRAV_NFP_SPEC:
                trav->curr = trav->curr->next;
                if (trav->curr != trav->head)
                        break;
                fallthrough;
        default:
                return NULL;
        }
        return trav;
}

static void *xt_mttg_seq_start(struct seq_file *seq, loff_t *pos,
    bool is_target)
{
        struct nf_mttg_trav *trav = seq->private;
        unsigned int j;

        trav->class = MTTG_TRAV_INIT;
        for (j = 0; j < *pos; ++j)
                if (xt_mttg_seq_next(seq, NULL, NULL, is_target) == NULL)
                        return NULL;
        return trav;
}

static void xt_mttg_seq_stop(struct seq_file *seq, void *v)
{
        uint8_t nfproto = (unsigned long)PDE_DATA(file_inode(seq->file));
        struct nf_mttg_trav *trav = seq->private;

        switch (trav->class) {
        case MTTG_TRAV_NFP_UNSPEC:
                mutex_unlock(&xt[NFPROTO_UNSPEC].mutex);
                break;
        case MTTG_TRAV_NFP_SPEC:
                mutex_unlock(&xt[nfproto].mutex);
                break;
        }
}

static void *xt_match_seq_start(struct seq_file *seq, loff_t *pos)
{
        return xt_mttg_seq_start(seq, pos, false);
}

static void *xt_match_seq_next(struct seq_file *seq, void *v, loff_t *ppos)
{
        return xt_mttg_seq_next(seq, v, ppos, false);
}

static int xt_match_seq_show(struct seq_file *seq, void *v)
{
        const struct nf_mttg_trav *trav = seq->private;
        const struct xt_match *match;

        switch (trav->class) {
        case MTTG_TRAV_NFP_UNSPEC:
        case MTTG_TRAV_NFP_SPEC:
                if (trav->curr == trav->head)
                        return 0;
                match = list_entry(trav->curr, struct xt_match, list);
                if (*match->name)
                        seq_printf(seq, "%s\n", match->name);
        }
        return 0;
}

static const struct seq_operations xt_match_seq_ops = {
        .start  = xt_match_seq_start,
        .next   = xt_match_seq_next,
        .stop   = xt_mttg_seq_stop,
        .show   = xt_match_seq_show,
};

static void *xt_target_seq_start(struct seq_file *seq, loff_t *pos)
{
        return xt_mttg_seq_start(seq, pos, true);
}

static void *xt_target_seq_next(struct seq_file *seq, void *v, loff_t *ppos)
{
        return xt_mttg_seq_next(seq, v, ppos, true);
}

static int xt_target_seq_show(struct seq_file *seq, void *v)
{
        const struct nf_mttg_trav *trav = seq->private;
        const struct xt_target *target;

        switch (trav->class) {
        case MTTG_TRAV_NFP_UNSPEC:
        case MTTG_TRAV_NFP_SPEC:
                if (trav->curr == trav->head)
                        return 0;
                target = list_entry(trav->curr, struct xt_target, list);
                if (*target->name)
                        seq_printf(seq, "%s\n", target->name);
        }
        return 0;
}

static const struct seq_operations xt_target_seq_ops = {
        .start  = xt_target_seq_start,
        .next   = xt_target_seq_next,
        .stop   = xt_mttg_seq_stop,
        .show   = xt_target_seq_show,
};

#define FORMAT_TABLES   "_tables_names"
#define FORMAT_MATCHES  "_tables_matches"
#define FORMAT_TARGETS  "_tables_targets"

#endif /* CONFIG_PROC_FS */

/**
 * xt_hook_ops_alloc - set up hooks for a new table
 * @table:      table with metadata needed to set up hooks
 * @fn:         Hook function
 *
 * This function will create the nf_hook_ops that the x_table needs
 * to hand to xt_hook_link_net().
 */
struct nf_hook_ops *
xt_hook_ops_alloc(const struct xt_table *table, nf_hookfn *fn)
{
        unsigned int hook_mask = table->valid_hooks;
        uint8_t i, num_hooks = hweight32(hook_mask);
        uint8_t hooknum;
        struct nf_hook_ops *ops;

        if (!num_hooks)
                return ERR_PTR(-EINVAL);

        ops = kcalloc(num_hooks, sizeof(*ops), GFP_KERNEL);
        if (ops == NULL)
                return ERR_PTR(-ENOMEM);

        for (i = 0, hooknum = 0; i < num_hooks && hook_mask != 0;
             hook_mask >>= 1, ++hooknum) {
                if (!(hook_mask & 1))
                        continue;
                ops[i].hook     = fn;
                ops[i].pf       = table->af;
                ops[i].hooknum  = hooknum;
                ops[i].priority = table->priority;
                ++i;
        }

        return ops;
}
EXPORT_SYMBOL_GPL(xt_hook_ops_alloc);

int xt_proto_init(struct net *net, u_int8_t af)
{
#ifdef CONFIG_PROC_FS
        char buf[XT_FUNCTION_MAXNAMELEN];
        struct proc_dir_entry *proc;
        kuid_t root_uid;
        kgid_t root_gid;
#endif

        if (af >= ARRAY_SIZE(xt_prefix))
                return -EINVAL;


#ifdef CONFIG_PROC_FS
        root_uid = make_kuid(net->user_ns, 0);
        root_gid = make_kgid(net->user_ns, 0);

        strlcpy(buf, xt_prefix[af], sizeof(buf));
        strlcat(buf, FORMAT_TABLES, sizeof(buf));
        proc = proc_create_net_data(buf, 0440, net->proc_net, &xt_table_seq_ops,
                        sizeof(struct seq_net_private),
                        (void *)(unsigned long)af);
        if (!proc)
                goto out;
        if (uid_valid(root_uid) && gid_valid(root_gid))
                proc_set_user(proc, root_uid, root_gid);

        strlcpy(buf, xt_prefix[af], sizeof(buf));
        strlcat(buf, FORMAT_MATCHES, sizeof(buf));
        proc = proc_create_seq_private(buf, 0440, net->proc_net,
                        &xt_match_seq_ops, sizeof(struct nf_mttg_trav),
                        (void *)(unsigned long)af);
        if (!proc)
                goto out_remove_tables;
        if (uid_valid(root_uid) && gid_valid(root_gid))
                proc_set_user(proc, root_uid, root_gid);

        strlcpy(buf, xt_prefix[af], sizeof(buf));
        strlcat(buf, FORMAT_TARGETS, sizeof(buf));
        proc = proc_create_seq_private(buf, 0440, net->proc_net,
                         &xt_target_seq_ops, sizeof(struct nf_mttg_trav),
                         (void *)(unsigned long)af);
        if (!proc)
                goto out_remove_matches;
        if (uid_valid(root_uid) && gid_valid(root_gid))
                proc_set_user(proc, root_uid, root_gid);
#endif

        return 0;

#ifdef CONFIG_PROC_FS
out_remove_matches:
        strlcpy(buf, xt_prefix[af], sizeof(buf));
        strlcat(buf, FORMAT_MATCHES, sizeof(buf));
        remove_proc_entry(buf, net->proc_net);

out_remove_tables:
        strlcpy(buf, xt_prefix[af], sizeof(buf));
        strlcat(buf, FORMAT_TABLES, sizeof(buf));
        remove_proc_entry(buf, net->proc_net);
out:
        return -1;
#endif
}
EXPORT_SYMBOL_GPL(xt_proto_init);

void xt_proto_fini(struct net *net, u_int8_t af)
{
#ifdef CONFIG_PROC_FS
        char buf[XT_FUNCTION_MAXNAMELEN];

        strlcpy(buf, xt_prefix[af], sizeof(buf));
        strlcat(buf, FORMAT_TABLES, sizeof(buf));
        remove_proc_entry(buf, net->proc_net);

        strlcpy(buf, xt_prefix[af], sizeof(buf));
        strlcat(buf, FORMAT_TARGETS, sizeof(buf));
        remove_proc_entry(buf, net->proc_net);

        strlcpy(buf, xt_prefix[af], sizeof(buf));
        strlcat(buf, FORMAT_MATCHES, sizeof(buf));
        remove_proc_entry(buf, net->proc_net);
#endif /*CONFIG_PROC_FS*/
}
EXPORT_SYMBOL_GPL(xt_proto_fini);

/**
 * xt_percpu_counter_alloc - allocate x_tables rule counter
 *
 * @state: pointer to xt_percpu allocation state
 * @counter: pointer to counter struct inside the ip(6)/arpt_entry struct
 *
 * On SMP, the packet counter [ ip(6)t_entry->counters.pcnt ] will then
 * contain the address of the real (percpu) counter.
 *
 * Rule evaluation needs to use xt_get_this_cpu_counter() helper
 * to fetch the real percpu counter.
 *
 * To speed up allocation and improve data locality, a 4kb block is
 * allocated.  Freeing any counter may free an entire block, so all
 * counters allocated using the same state must be freed at the same
 * time.
 *
 * xt_percpu_counter_alloc_state contains the base address of the
 * allocated page and the current sub-offset.
 *
 * returns false on error.
 */
bool xt_percpu_counter_alloc(struct xt_percpu_counter_alloc_state *state,
                             struct xt_counters *counter)
{
        BUILD_BUG_ON(XT_PCPU_BLOCK_SIZE < (sizeof(*counter) * 2));

        if (nr_cpu_ids <= 1)
                return true;

        if (!state->mem) {
                state->mem = __alloc_percpu(XT_PCPU_BLOCK_SIZE,
                                            XT_PCPU_BLOCK_SIZE);
                if (!state->mem)
                        return false;
        }
        counter->pcnt = (__force unsigned long)(state->mem + state->off);
        state->off += sizeof(*counter);
        if (state->off > (XT_PCPU_BLOCK_SIZE - sizeof(*counter))) {
                state->mem = NULL;
                state->off = 0;
        }
        return true;
}
EXPORT_SYMBOL_GPL(xt_percpu_counter_alloc);

void xt_percpu_counter_free(struct xt_counters *counters)
{
        unsigned long pcnt = counters->pcnt;

        if (nr_cpu_ids > 1 && (pcnt & (XT_PCPU_BLOCK_SIZE - 1)) == 0)
                free_percpu((void __percpu *)pcnt);
}
EXPORT_SYMBOL_GPL(xt_percpu_counter_free);

static int __net_init xt_net_init(struct net *net)
{
        int i;

        for (i = 0; i < NFPROTO_NUMPROTO; i++)
                INIT_LIST_HEAD(&net->xt.tables[i]);
        return 0;
}

static void __net_exit xt_net_exit(struct net *net)
{
        int i;

        for (i = 0; i < NFPROTO_NUMPROTO; i++)
                WARN_ON_ONCE(!list_empty(&net->xt.tables[i]));
}

static struct pernet_operations xt_net_ops = {
        .init = xt_net_init,
        .exit = xt_net_exit,
};

static int __init xt_init(void)
{
        unsigned int i;
        int rv;

        for_each_possible_cpu(i) {
                seqcount_init(&per_cpu(xt_recseq, i));
        }

        xt = kcalloc(NFPROTO_NUMPROTO, sizeof(struct xt_af), GFP_KERNEL);
        if (!xt)
                return -ENOMEM;

        for (i = 0; i < NFPROTO_NUMPROTO; i++) {
                mutex_init(&xt[i].mutex);
#ifdef CONFIG_COMPAT
                mutex_init(&xt[i].compat_mutex);
                xt[i].compat_tab = NULL;
#endif
                INIT_LIST_HEAD(&xt[i].target);
                INIT_LIST_HEAD(&xt[i].match);
        }
        rv = register_pernet_subsys(&xt_net_ops);
        if (rv < 0)
                kfree(xt);
        return rv;
}

static void __exit xt_fini(void)
{
        unregister_pernet_subsys(&xt_net_ops);
        kfree(xt);
}

module_init(xt_init);
module_exit(xt_fini);