net/netlink/policy.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0
 /*
  * NETLINK      Policy advertisement to userspace
  *
  * 		Authors:	Johannes Berg <johannes@sipsolutions.net>
  *
  * Copyright 2019 Intel Corporation
  */

 #include <linux/kernel.h>
 #include <linux/errno.h>
 #include <linux/types.h>
 #include <net/netlink.h>

 #define INITIAL_POLICIES_ALLOC	10

 struct netlink_policy_dump_state {
 	unsigned int policy_idx;
 	unsigned int attr_idx;
 	unsigned int n_alloc;
 	struct {
 		const struct nla_policy *policy;
 		unsigned int maxtype;
 	} policies[];
 };

 static int add_policy(struct netlink_policy_dump_state **statep,
 		      const struct nla_policy *policy,
 		      unsigned int maxtype)
 {
 	struct netlink_policy_dump_state *state = *statep;
 	unsigned int n_alloc, i;

 	if (!policy || !maxtype)
 		return 0;

 	for (i = 0; i < state->n_alloc; i++) {
 		if (state->policies[i].policy == policy &&
 		    state->policies[i].maxtype == maxtype)
 			return 0;

 		if (!state->policies[i].policy) {
 			state->policies[i].policy = policy;
 			state->policies[i].maxtype = maxtype;
 			return 0;
 		}
 	}

 	n_alloc = state->n_alloc + INITIAL_POLICIES_ALLOC;
 	state = krealloc(state, struct_size(state, policies, n_alloc),
 			 GFP_KERNEL);
 	if (!state)
 		return -ENOMEM;

 	memset(&state->policies[state->n_alloc], 0,
 	       flex_array_size(state, policies, n_alloc - state->n_alloc));

 	state->policies[state->n_alloc].policy = policy;
 	state->policies[state->n_alloc].maxtype = maxtype;
 	state->n_alloc = n_alloc;
 	*statep = state;

 	return 0;
 }

 /**
  * netlink_policy_dump_get_policy_idx - retrieve policy index
  * @state: the policy dump state
  * @policy: the policy to find
  * @maxtype: the policy's maxattr
  *
  * Returns: the index of the given policy in the dump state
  *
  * Call this to find a policy index when you've added multiple and e.g.
  * need to tell userspace which command has which policy (by index).
  *
  * Note: this will WARN and return 0 if the policy isn't found, which
  *	 means it wasn't added in the first place, which would be an
  *	 internal consistency bug.
  */
 int netlink_policy_dump_get_policy_idx(struct netlink_policy_dump_state *state,
 				       const struct nla_policy *policy,
 				       unsigned int maxtype)
 {
 	unsigned int i;

 	if (WARN_ON(!policy || !maxtype))
                 return 0;

 	for (i = 0; i < state->n_alloc; i++) {
 		if (state->policies[i].policy == policy &&
 		    state->policies[i].maxtype == maxtype)
 			return i;
 	}

 	WARN_ON(1);
 	return 0;
 }

 static struct netlink_policy_dump_state *alloc_state(void)
 {
 	struct netlink_policy_dump_state *state;

 	state = kzalloc(struct_size(state, policies, INITIAL_POLICIES_ALLOC),
 			GFP_KERNEL);
 	if (!state)
 		return ERR_PTR(-ENOMEM);
 	state->n_alloc = INITIAL_POLICIES_ALLOC;

 	return state;
 }

 /**
  * netlink_policy_dump_add_policy - add a policy to the dump
  * @pstate: state to add to, may be reallocated, must be %NULL the first time
  * @policy: the new policy to add to the dump
  * @maxtype: the new policy's max attr type
  *
  * Returns: 0 on success, a negative error code otherwise.
  *
  * Call this to allocate a policy dump state, and to add policies to it. This
  * should be called from the dump start() callback.
  *
  * Note: on failures, any previously allocated state is freed.
  */
 int netlink_policy_dump_add_policy(struct netlink_policy_dump_state **pstate,
 				   const struct nla_policy *policy,
 				   unsigned int maxtype)
 {
 	struct netlink_policy_dump_state *state = *pstate;
 	unsigned int policy_idx;
 	int err;

 	if (!state) {
 		state = alloc_state();
 		if (IS_ERR(state))
 			return PTR_ERR(state);
 	}

 	/*
 	 * walk the policies and nested ones first, and build
 	 * a linear list of them.
 	 */

 	err = add_policy(&state, policy, maxtype);
 	if (err)
 		goto err_try_undo;

 	for (policy_idx = 0;
 	     policy_idx < state->n_alloc && state->policies[policy_idx].policy;
 	     policy_idx++) {
 		const struct nla_policy *policy;
 		unsigned int type;

 		policy = state->policies[policy_idx].policy;

 		for (type = 0;
 		     type <= state->policies[policy_idx].maxtype;
 		     type++) {
 			switch (policy[type].type) {
 			case NLA_NESTED:
 			case NLA_NESTED_ARRAY:
 				err = add_policy(&state,
 						 policy[type].nested_policy,
 						 policy[type].len);
 				if (err)
 					goto err_try_undo;
 				break;
 			default:
 				break;
 			}
 		}
 	}

 	*pstate = state;
 	return 0;

 err_try_undo:
 	/* Try to preserve reasonable unwind semantics - if we're starting from
 	 * scratch clean up fully, otherwise record what we got and caller will.
 	 */
 	if (!*pstate)
 		netlink_policy_dump_free(state);
 	else
 		*pstate = state;
 	return err;
 }

 static bool
 netlink_policy_dump_finished(struct netlink_policy_dump_state *state)
 {
 	return state->policy_idx >= state->n_alloc ||
 	       !state->policies[state->policy_idx].policy;
 }

 /**
  * netlink_policy_dump_loop - dumping loop indicator
  * @state: the policy dump state
  *
  * Returns: %true if the dump continues, %false otherwise
  *
  * Note: this frees the dump state when finishing
  */
 bool netlink_policy_dump_loop(struct netlink_policy_dump_state *state)
 {
 	return !netlink_policy_dump_finished(state);
 }

 int netlink_policy_dump_attr_size_estimate(const struct nla_policy *pt)
 {
 	/* nested + type */
 	int common = 2 * nla_attr_size(sizeof(u32));

 	switch (pt->type) {
 	case NLA_UNSPEC:
 	case NLA_REJECT:
 		/* these actually don't need any space */
 		return 0;
 	case NLA_NESTED:
 	case NLA_NESTED_ARRAY:
 		/* common, policy idx, policy maxattr */
 		return common + 2 * nla_attr_size(sizeof(u32));
 	case NLA_U8:
 	case NLA_U16:
 	case NLA_U32:
 	case NLA_U64:
 	case NLA_MSECS:
 	case NLA_S8:
 	case NLA_S16:
 	case NLA_S32:
 	case NLA_S64:
 		/* maximum is common, u64 min/max with padding */
 		return common +
 		       2 * (nla_attr_size(0) + nla_attr_size(sizeof(u64)));
 	case NLA_BITFIELD32:
 		return common + nla_attr_size(sizeof(u32));
 	case NLA_STRING:
 	case NLA_NUL_STRING:
 	case NLA_BINARY:
 		/* maximum is common, u32 min-length/max-length */
 		return common + 2 * nla_attr_size(sizeof(u32));
 	case NLA_FLAG:
 		return common;
 	}

 	/* this should then cause a warning later */
 	return 0;
 }

 static int
 __netlink_policy_dump_write_attr(struct netlink_policy_dump_state *state,
 				 struct sk_buff *skb,
 				 const struct nla_policy *pt,
 				 int nestattr)
 {
 	int estimate = netlink_policy_dump_attr_size_estimate(pt);
 	enum netlink_attribute_type type;
 	struct nlattr *attr;

 	attr = nla_nest_start(skb, nestattr);
 	if (!attr)
 		return -ENOBUFS;

 	switch (pt->type) {
 	default:
 	case NLA_UNSPEC:
 	case NLA_REJECT:
 		/* skip - use NLA_MIN_LEN to advertise such */
 		nla_nest_cancel(skb, attr);
 		return -ENODATA;
 	case NLA_NESTED:
 		type = NL_ATTR_TYPE_NESTED;
 		fallthrough;
 	case NLA_NESTED_ARRAY:
 		if (pt->type == NLA_NESTED_ARRAY)
 			type = NL_ATTR_TYPE_NESTED_ARRAY;
 		if (state && pt->nested_policy && pt->len &&
 		    (nla_put_u32(skb, NL_POLICY_TYPE_ATTR_POLICY_IDX,
 				 netlink_policy_dump_get_policy_idx(state,
 								    pt->nested_policy,
 								    pt->len)) ||
 		     nla_put_u32(skb, NL_POLICY_TYPE_ATTR_POLICY_MAXTYPE,
 				 pt->len)))
 			goto nla_put_failure;
 		break;
 	case NLA_U8:
 	case NLA_U16:
 	case NLA_U32:
 	case NLA_U64:
 	case NLA_MSECS: {
 		struct netlink_range_validation range;

 		if (pt->type == NLA_U8)
 			type = NL_ATTR_TYPE_U8;
 		else if (pt->type == NLA_U16)
 			type = NL_ATTR_TYPE_U16;
 		else if (pt->type == NLA_U32)
 			type = NL_ATTR_TYPE_U32;
 		else
 			type = NL_ATTR_TYPE_U64;

 		if (pt->validation_type == NLA_VALIDATE_MASK) {
 			if (nla_put_u64_64bit(skb, NL_POLICY_TYPE_ATTR_MASK,
 					      pt->mask,
 					      NL_POLICY_TYPE_ATTR_PAD))
 				goto nla_put_failure;
 			break;
 		}

 		nla_get_range_unsigned(pt, &range);

 		if (nla_put_u64_64bit(skb, NL_POLICY_TYPE_ATTR_MIN_VALUE_U,
 				      range.min, NL_POLICY_TYPE_ATTR_PAD) ||
 		    nla_put_u64_64bit(skb, NL_POLICY_TYPE_ATTR_MAX_VALUE_U,
 				      range.max, NL_POLICY_TYPE_ATTR_PAD))
 			goto nla_put_failure;
 		break;
 	}
 	case NLA_S8:
 	case NLA_S16:
 	case NLA_S32:
 	case NLA_S64: {
 		struct netlink_range_validation_signed range;

 		if (pt->type == NLA_S8)
 			type = NL_ATTR_TYPE_S8;
 		else if (pt->type == NLA_S16)
 			type = NL_ATTR_TYPE_S16;
 		else if (pt->type == NLA_S32)
 			type = NL_ATTR_TYPE_S32;
 		else
 			type = NL_ATTR_TYPE_S64;

 		nla_get_range_signed(pt, &range);

 		if (nla_put_s64(skb, NL_POLICY_TYPE_ATTR_MIN_VALUE_S,
 				range.min, NL_POLICY_TYPE_ATTR_PAD) ||
 		    nla_put_s64(skb, NL_POLICY_TYPE_ATTR_MAX_VALUE_S,
 				range.max, NL_POLICY_TYPE_ATTR_PAD))
 			goto nla_put_failure;
 		break;
 	}
 	case NLA_BITFIELD32:
 		type = NL_ATTR_TYPE_BITFIELD32;
 		if (nla_put_u32(skb, NL_POLICY_TYPE_ATTR_BITFIELD32_MASK,
 				pt->bitfield32_valid))
 			goto nla_put_failure;
 		break;
 	case NLA_STRING:
 	case NLA_NUL_STRING:
 	case NLA_BINARY:
 		if (pt->type == NLA_STRING)
 			type = NL_ATTR_TYPE_STRING;
 		else if (pt->type == NLA_NUL_STRING)
 			type = NL_ATTR_TYPE_NUL_STRING;
 		else
 			type = NL_ATTR_TYPE_BINARY;

 		if (pt->validation_type == NLA_VALIDATE_RANGE ||
 		    pt->validation_type == NLA_VALIDATE_RANGE_WARN_TOO_LONG) {
 			struct netlink_range_validation range;

 			nla_get_range_unsigned(pt, &range);

 			if (range.min &&
 			    nla_put_u32(skb, NL_POLICY_TYPE_ATTR_MIN_LENGTH,
 					range.min))
 				goto nla_put_failure;

 			if (range.max < U16_MAX &&
 			    nla_put_u32(skb, NL_POLICY_TYPE_ATTR_MAX_LENGTH,
 					range.max))
 				goto nla_put_failure;
 		} else if (pt->len &&
 			   nla_put_u32(skb, NL_POLICY_TYPE_ATTR_MAX_LENGTH,
 				       pt->len)) {
 			goto nla_put_failure;
 		}
 		break;
 	case NLA_FLAG:
 		type = NL_ATTR_TYPE_FLAG;
 		break;
 	}

 	if (nla_put_u32(skb, NL_POLICY_TYPE_ATTR_TYPE, type))
 		goto nla_put_failure;

 	nla_nest_end(skb, attr);
 	WARN_ON(attr->nla_len > estimate);

 	return 0;
 nla_put_failure:
 	nla_nest_cancel(skb, attr);
 	return -ENOBUFS;
 }

 /**
  * netlink_policy_dump_write_attr - write a given attribute policy
  * @skb: the message skb to write to
  * @pt: the attribute's policy
  * @nestattr: the nested attribute ID to use
  *
  * Returns: 0 on success, an error code otherwise; -%ENODATA is
  *	    special, indicating that there's no policy data and
  *	    the attribute is generally rejected.
  */
 int netlink_policy_dump_write_attr(struct sk_buff *skb,
 				   const struct nla_policy *pt,
 				   int nestattr)
 {
 	return __netlink_policy_dump_write_attr(NULL, skb, pt, nestattr);
 }

 /**
  * netlink_policy_dump_write - write current policy dump attributes
  * @skb: the message skb to write to
  * @state: the policy dump state
  *
  * Returns: 0 on success, an error code otherwise
  */
 int netlink_policy_dump_write(struct sk_buff *skb,
 			      struct netlink_policy_dump_state *state)
 {
 	const struct nla_policy *pt;
 	struct nlattr *policy;
 	bool again;
 	int err;

 send_attribute:
 	again = false;

 	pt = &state->policies[state->policy_idx].policy[state->attr_idx];

 	policy = nla_nest_start(skb, state->policy_idx);
 	if (!policy)
 		return -ENOBUFS;

 	err = __netlink_policy_dump_write_attr(state, skb, pt, state->attr_idx);
 	if (err == -ENODATA) {
 		nla_nest_cancel(skb, policy);
 		again = true;
 		goto next;
 	} else if (err) {
 		goto nla_put_failure;
 	}

 	/* finish and move state to next attribute */
 	nla_nest_end(skb, policy);

 next:
 	state->attr_idx += 1;
 	if (state->attr_idx > state->policies[state->policy_idx].maxtype) {
 		state->attr_idx = 0;
 		state->policy_idx++;
 	}

 	if (again) {
 		if (netlink_policy_dump_finished(state))
 			return -ENODATA;
 		goto send_attribute;
 	}

 	return 0;

 nla_put_failure:
 	nla_nest_cancel(skb, policy);
 	return -ENOBUFS;
 }

 /**
  * netlink_policy_dump_free - free policy dump state
  * @state: the policy dump state to free
  *
  * Call this from the done() method to ensure dump state is freed.
  */
 void netlink_policy_dump_free(struct netlink_policy_dump_state *state)
 {
 	kfree(state);
 }
	// SPDX-License-Identifier: GPL-2.0
	/*
	* NETLINK Policy advertisement to userspace
	*
	* Authors: Johannes Berg <johannes@sipsolutions.net>
	*
	* Copyright 2019 Intel Corporation
	*/

	#include <linux/kernel.h>
	#include <linux/errno.h>
	#include <linux/types.h>
	#include <net/netlink.h>

	#define INITIAL_POLICIES_ALLOC 10

	struct netlink_policy_dump_state {
	unsigned int policy_idx;
	unsigned int attr_idx;
	unsigned int n_alloc;
	struct {
	const struct nla_policy *policy;
	unsigned int maxtype;
	} policies[];
	};

	static int add_policy(struct netlink_policy_dump_state **statep,
	const struct nla_policy *policy,
	unsigned int maxtype)
	{
	struct netlink_policy_dump_state state = statep;
	unsigned int n_alloc, i;

	if (!policy \|\| !maxtype)
	return 0;

	for (i = 0; i < state->n_alloc; i++) {
	if (state->policies[i].policy == policy &&
	state->policies[i].maxtype == maxtype)
	return 0;

	if (!state->policies[i].policy) {
	state->policies[i].policy = policy;
	state->policies[i].maxtype = maxtype;
	return 0;
	}
	}

	n_alloc = state->n_alloc + INITIAL_POLICIES_ALLOC;
	state = krealloc(state, struct_size(state, policies, n_alloc),
	GFP_KERNEL);
	if (!state)
	return -ENOMEM;

	memset(&state->policies[state->n_alloc], 0,
	flex_array_size(state, policies, n_alloc - state->n_alloc));

	state->policies[state->n_alloc].policy = policy;
	state->policies[state->n_alloc].maxtype = maxtype;
	state->n_alloc = n_alloc;
	*statep = state;

	return 0;
	}

	/**
	* netlink_policy_dump_get_policy_idx - retrieve policy index
	* @state: the policy dump state
	* @policy: the policy to find
	* @maxtype: the policy's maxattr
	*
	* Returns: the index of the given policy in the dump state
	*
	* Call this to find a policy index when you've added multiple and e.g.
	* need to tell userspace which command has which policy (by index).
	*
	* Note: this will WARN and return 0 if the policy isn't found, which
	* means it wasn't added in the first place, which would be an
	* internal consistency bug.
	*/
	int netlink_policy_dump_get_policy_idx(struct netlink_policy_dump_state *state,
	const struct nla_policy *policy,
	unsigned int maxtype)
	{
	unsigned int i;

	if (WARN_ON(!policy \|\| !maxtype))
	return 0;

	for (i = 0; i < state->n_alloc; i++) {
	if (state->policies[i].policy == policy &&
	state->policies[i].maxtype == maxtype)
	return i;
	}

	WARN_ON(1);
	return 0;
	}

	static struct netlink_policy_dump_state *alloc_state(void)
	{
	struct netlink_policy_dump_state *state;

	state = kzalloc(struct_size(state, policies, INITIAL_POLICIES_ALLOC),
	GFP_KERNEL);
	if (!state)
	return ERR_PTR(-ENOMEM);
	state->n_alloc = INITIAL_POLICIES_ALLOC;

	return state;
	}

	/**
	* netlink_policy_dump_add_policy - add a policy to the dump
	* @pstate: state to add to, may be reallocated, must be %NULL the first time
	* @policy: the new policy to add to the dump
	* @maxtype: the new policy's max attr type
	*
	* Returns: 0 on success, a negative error code otherwise.
	*
	* Call this to allocate a policy dump state, and to add policies to it. This
	* should be called from the dump start() callback.
	*
	* Note: on failures, any previously allocated state is freed.
	*/
	int netlink_policy_dump_add_policy(struct netlink_policy_dump_state **pstate,
	const struct nla_policy *policy,
	unsigned int maxtype)
	{
	struct netlink_policy_dump_state state = pstate;
	unsigned int policy_idx;
	int err;

	if (!state) {
	state = alloc_state();
	if (IS_ERR(state))
	return PTR_ERR(state);
	}

	/*
	* walk the policies and nested ones first, and build
	* a linear list of them.
	*/

	err = add_policy(&state, policy, maxtype);
	if (err)
	goto err_try_undo;

	for (policy_idx = 0;
	policy_idx < state->n_alloc && state->policies[policy_idx].policy;
	policy_idx++) {
	const struct nla_policy *policy;
	unsigned int type;

	policy = state->policies[policy_idx].policy;

	for (type = 0;
	type <= state->policies[policy_idx].maxtype;
	type++) {
	switch (policy[type].type) {
	case NLA_NESTED:
	case NLA_NESTED_ARRAY:
	err = add_policy(&state,
	policy[type].nested_policy,
	policy[type].len);
	if (err)
	goto err_try_undo;
	break;
	default:
	break;
	}
	}
	}

	*pstate = state;
	return 0;

	err_try_undo:
	/* Try to preserve reasonable unwind semantics - if we're starting from
	* scratch clean up fully, otherwise record what we got and caller will.
	*/
	if (!*pstate)
	netlink_policy_dump_free(state);
	else
	*pstate = state;
	return err;
	}

	static bool
	netlink_policy_dump_finished(struct netlink_policy_dump_state *state)
	{
	return state->policy_idx >= state->n_alloc \|\|
	!state->policies[state->policy_idx].policy;
	}

	/**
	* netlink_policy_dump_loop - dumping loop indicator
	* @state: the policy dump state
	*
	* Returns: %true if the dump continues, %false otherwise
	*
	* Note: this frees the dump state when finishing
	*/
	bool netlink_policy_dump_loop(struct netlink_policy_dump_state *state)
	{
	return !netlink_policy_dump_finished(state);
	}

	int netlink_policy_dump_attr_size_estimate(const struct nla_policy *pt)
	{
	/* nested + type */
	int common = 2 * nla_attr_size(sizeof(u32));

	switch (pt->type) {
	case NLA_UNSPEC:
	case NLA_REJECT:
	/* these actually don't need any space */
	return 0;
	case NLA_NESTED:
	case NLA_NESTED_ARRAY:
	/* common, policy idx, policy maxattr */
	return common + 2 * nla_attr_size(sizeof(u32));
	case NLA_U8:
	case NLA_U16:
	case NLA_U32:
	case NLA_U64:
	case NLA_MSECS:
	case NLA_S8:
	case NLA_S16:
	case NLA_S32:
	case NLA_S64:
	/* maximum is common, u64 min/max with padding */
	return common +
	2 * (nla_attr_size(0) + nla_attr_size(sizeof(u64)));
	case NLA_BITFIELD32:
	return common + nla_attr_size(sizeof(u32));
	case NLA_STRING:
	case NLA_NUL_STRING:
	case NLA_BINARY:
	/* maximum is common, u32 min-length/max-length */
	return common + 2 * nla_attr_size(sizeof(u32));
	case NLA_FLAG:
	return common;
	}

	/* this should then cause a warning later */
	return 0;
	}

	static int
	__netlink_policy_dump_write_attr(struct netlink_policy_dump_state *state,
	struct sk_buff *skb,
	const struct nla_policy *pt,
	int nestattr)
	{
	int estimate = netlink_policy_dump_attr_size_estimate(pt);
	enum netlink_attribute_type type;
	struct nlattr *attr;

	attr = nla_nest_start(skb, nestattr);
	if (!attr)
	return -ENOBUFS;

	switch (pt->type) {
	default:
	case NLA_UNSPEC:
	case NLA_REJECT:
	/* skip - use NLA_MIN_LEN to advertise such */
	nla_nest_cancel(skb, attr);
	return -ENODATA;
	case NLA_NESTED:
	type = NL_ATTR_TYPE_NESTED;
	fallthrough;
	case NLA_NESTED_ARRAY:
	if (pt->type == NLA_NESTED_ARRAY)
	type = NL_ATTR_TYPE_NESTED_ARRAY;
	if (state && pt->nested_policy && pt->len &&
	(nla_put_u32(skb, NL_POLICY_TYPE_ATTR_POLICY_IDX,
	netlink_policy_dump_get_policy_idx(state,
	pt->nested_policy,
	pt->len)) \|\|
	nla_put_u32(skb, NL_POLICY_TYPE_ATTR_POLICY_MAXTYPE,
	pt->len)))
	goto nla_put_failure;
	break;
	case NLA_U8:
	case NLA_U16:
	case NLA_U32:
	case NLA_U64:
	case NLA_MSECS: {
	struct netlink_range_validation range;

	if (pt->type == NLA_U8)
	type = NL_ATTR_TYPE_U8;
	else if (pt->type == NLA_U16)
	type = NL_ATTR_TYPE_U16;
	else if (pt->type == NLA_U32)
	type = NL_ATTR_TYPE_U32;
	else
	type = NL_ATTR_TYPE_U64;

	if (pt->validation_type == NLA_VALIDATE_MASK) {
	if (nla_put_u64_64bit(skb, NL_POLICY_TYPE_ATTR_MASK,
	pt->mask,
	NL_POLICY_TYPE_ATTR_PAD))
	goto nla_put_failure;
	break;
	}

	nla_get_range_unsigned(pt, &range);

	if (nla_put_u64_64bit(skb, NL_POLICY_TYPE_ATTR_MIN_VALUE_U,
	range.min, NL_POLICY_TYPE_ATTR_PAD) \|\|
	nla_put_u64_64bit(skb, NL_POLICY_TYPE_ATTR_MAX_VALUE_U,
	range.max, NL_POLICY_TYPE_ATTR_PAD))
	goto nla_put_failure;
	break;
	}
	case NLA_S8:
	case NLA_S16:
	case NLA_S32:
	case NLA_S64: {
	struct netlink_range_validation_signed range;

	if (pt->type == NLA_S8)
	type = NL_ATTR_TYPE_S8;
	else if (pt->type == NLA_S16)
	type = NL_ATTR_TYPE_S16;
	else if (pt->type == NLA_S32)
	type = NL_ATTR_TYPE_S32;
	else
	type = NL_ATTR_TYPE_S64;

	nla_get_range_signed(pt, &range);

	if (nla_put_s64(skb, NL_POLICY_TYPE_ATTR_MIN_VALUE_S,
	range.min, NL_POLICY_TYPE_ATTR_PAD) \|\|
	nla_put_s64(skb, NL_POLICY_TYPE_ATTR_MAX_VALUE_S,
	range.max, NL_POLICY_TYPE_ATTR_PAD))
	goto nla_put_failure;
	break;
	}
	case NLA_BITFIELD32:
	type = NL_ATTR_TYPE_BITFIELD32;
	if (nla_put_u32(skb, NL_POLICY_TYPE_ATTR_BITFIELD32_MASK,
	pt->bitfield32_valid))
	goto nla_put_failure;
	break;
	case NLA_STRING:
	case NLA_NUL_STRING:
	case NLA_BINARY:
	if (pt->type == NLA_STRING)
	type = NL_ATTR_TYPE_STRING;
	else if (pt->type == NLA_NUL_STRING)
	type = NL_ATTR_TYPE_NUL_STRING;
	else
	type = NL_ATTR_TYPE_BINARY;

	if (pt->validation_type == NLA_VALIDATE_RANGE \|\|
	pt->validation_type == NLA_VALIDATE_RANGE_WARN_TOO_LONG) {
	struct netlink_range_validation range;

	nla_get_range_unsigned(pt, &range);

	if (range.min &&
	nla_put_u32(skb, NL_POLICY_TYPE_ATTR_MIN_LENGTH,
	range.min))
	goto nla_put_failure;

	if (range.max < U16_MAX &&
	nla_put_u32(skb, NL_POLICY_TYPE_ATTR_MAX_LENGTH,
	range.max))
	goto nla_put_failure;
	} else if (pt->len &&
	nla_put_u32(skb, NL_POLICY_TYPE_ATTR_MAX_LENGTH,
	pt->len)) {
	goto nla_put_failure;
	}
	break;
	case NLA_FLAG:
	type = NL_ATTR_TYPE_FLAG;
	break;
	}

	if (nla_put_u32(skb, NL_POLICY_TYPE_ATTR_TYPE, type))
	goto nla_put_failure;

	nla_nest_end(skb, attr);
	WARN_ON(attr->nla_len > estimate);

	return 0;
	nla_put_failure:
	nla_nest_cancel(skb, attr);
	return -ENOBUFS;
	}

	/**
	* netlink_policy_dump_write_attr - write a given attribute policy
	* @skb: the message skb to write to
	* @pt: the attribute's policy
	* @nestattr: the nested attribute ID to use
	*
	* Returns: 0 on success, an error code otherwise; -%ENODATA is
	* special, indicating that there's no policy data and
	* the attribute is generally rejected.
	*/
	int netlink_policy_dump_write_attr(struct sk_buff *skb,
	const struct nla_policy *pt,
	int nestattr)
	{
	return __netlink_policy_dump_write_attr(NULL, skb, pt, nestattr);
	}

	/**
	* netlink_policy_dump_write - write current policy dump attributes
	* @skb: the message skb to write to
	* @state: the policy dump state
	*
	* Returns: 0 on success, an error code otherwise
	*/
	int netlink_policy_dump_write(struct sk_buff *skb,
	struct netlink_policy_dump_state *state)
	{
	const struct nla_policy *pt;
	struct nlattr *policy;
	bool again;
	int err;

	send_attribute:
	again = false;

	pt = &state->policies[state->policy_idx].policy[state->attr_idx];

	policy = nla_nest_start(skb, state->policy_idx);
	if (!policy)
	return -ENOBUFS;

	err = __netlink_policy_dump_write_attr(state, skb, pt, state->attr_idx);
	if (err == -ENODATA) {
	nla_nest_cancel(skb, policy);
	again = true;
	goto next;
	} else if (err) {
	goto nla_put_failure;
	}

	/* finish and move state to next attribute */
	nla_nest_end(skb, policy);

	next:
	state->attr_idx += 1;
	if (state->attr_idx > state->policies[state->policy_idx].maxtype) {
	state->attr_idx = 0;
	state->policy_idx++;
	}

	if (again) {
	if (netlink_policy_dump_finished(state))
	return -ENODATA;
	goto send_attribute;
	}

	return 0;

	nla_put_failure:
	nla_nest_cancel(skb, policy);
	return -ENOBUFS;
	}

	/**
	* netlink_policy_dump_free - free policy dump state
	* @state: the policy dump state to free
	*
	* Call this from the done() method to ensure dump state is freed.
	*/
	void netlink_policy_dump_free(struct netlink_policy_dump_state *state)
	{
	kfree(state);
	}