text: // 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;
  
  	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;
  		}
  	}
  
  	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;
  
  	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;
  		}
  	}
  
  	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;
  
  	mutex_lock(&xt[af].mutex);
  	if (target == 1)
  		have_rev = target_revfn(af, name, revision, &best);
  	else
  		have_rev = match_revfn(af, name, revision, &best);
  	mutex_unlock(&xt[af].mutex);
  
  	/* 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 pad, 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));
  	pad = XT_ALIGN(match->matchsize) - match->matchsize;
  	if (pad > 0)
  		memset(m->data + match->matchsize, 0, pad);
  
  	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 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 kvmalloc_array(size, sizeof(unsigned int), GFP_KERNEL | __GFP_ZERO);
  
  }
  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_from_user - copy counters and metadata from userspace
   *
   * @user: src pointer to userspace memory
   * @len: alleged size of userspace memory
   * @info: where to store the xt_counters_info metadata
   * @compat: true if we setsockopt call is done by 32bit task on 64bit kernel
   *
   * 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 @compat is true, @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_from_user(const void __user *user, unsigned int len,
  				 struct xt_counters_info *info, bool compat)
  {
  	void *mem;
  	u64 size;
  
  #ifdef CONFIG_COMPAT
  	if (compat) {
  		/* 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_user(&compat_tmp, user, 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;
  		user += sizeof(compat_tmp);
  	} else
  #endif
  	{
  		if (len <= sizeof(*info))
  			return ERR_PTR(-EINVAL);
  
  		len -= sizeof(*info);
  		if (copy_from_user(info, user, sizeof(*info)) != 0)
  			return ERR_PTR(-EFAULT);
  
  		user += 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_user(mem, user, len) == 0)
  		return mem;
  
  	vfree(mem);
  	return ERR_PTR(-EFAULT);
  }
  EXPORT_SYMBOL_GPL(xt_copy_counters_from_user);
  
  #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 pad, 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));
  	pad = XT_ALIGN(target->targetsize) - target->targetsize;
  	if (pad > 0)
  		memset(t->data + target->targetsize, 0, pad);
  
  	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_wmb();
  
  	/*
  	 * 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));
  		}
  	}
  
  #ifdef CONFIG_AUDIT
  	if (audit_enabled) {
  		audit_log(audit_context(), GFP_KERNEL,
  			  AUDIT_NETFILTER_CFG,
  			  "table=%s family=%u entries=%u",
  			  table->name, table->af, private->number);
  	}
  #endif
  
  	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);
  	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;
  		/* fall through */
  	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);
  
  