// SPDX-License-Identifier: GPL-2.0
/*
* NETLINK Policy advertisement to userspace
*
* Authors: Johannes Berg <[email protected]>
*
* 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[] __counted_by(n_alloc);
};
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 old_n_alloc, 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;
old_n_alloc = state->n_alloc;
state->n_alloc = n_alloc;
memset(&state->policies[old_n_alloc], 0,
flex_array_size(state, policies, n_alloc - old_n_alloc));
state->policies[old_n_alloc].policy = policy;
state->policies[old_n_alloc].maxtype = maxtype;
*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:
case NLA_SINT:
case NLA_UINT:
/* 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_UINT:
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 if (pt->type == NLA_U64)
type = NL_ATTR_TYPE_U64;
else
type = NL_ATTR_TYPE_UINT;
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:
case NLA_SINT: {
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 if (pt->type == NLA_S64)
type = NL_ATTR_TYPE_S64;
else
type = NL_ATTR_TYPE_SINT;
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);
}
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