1// SPDX-License-Identifier: GPL-2.0
2/*
3 * NETLINK Policy advertisement to userspace
4 *
5 * Authors: Johannes Berg <johannes@sipsolutions.net>
6 *
7 * Copyright 2019 Intel Corporation
8 */
9
10#include <linux/kernel.h>
11#include <linux/errno.h>
12#include <linux/types.h>
13#include <net/netlink.h>
14
15#define INITIAL_POLICIES_ALLOC 10
16
17struct netlink_policy_dump_state {
18 unsigned int policy_idx;
19 unsigned int attr_idx;
20 unsigned int n_alloc;
21 struct {
22 const struct nla_policy *policy;
23 unsigned int maxtype;
24 } policies[] __counted_by(n_alloc);
25};
26
27static int add_policy(struct netlink_policy_dump_state **statep,
28 const struct nla_policy *policy,
29 unsigned int maxtype)
30{
31 struct netlink_policy_dump_state *state = *statep;
32 unsigned int old_n_alloc, n_alloc, i;
33
34 if (!policy || !maxtype)
35 return 0;
36
37 for (i = 0; i < state->n_alloc; i++) {
38 if (state->policies[i].policy == policy &&
39 state->policies[i].maxtype == maxtype)
40 return 0;
41
42 if (!state->policies[i].policy) {
43 state->policies[i].policy = policy;
44 state->policies[i].maxtype = maxtype;
45 return 0;
46 }
47 }
48
49 n_alloc = state->n_alloc + INITIAL_POLICIES_ALLOC;
50 state = krealloc(state, struct_size(state, policies, n_alloc),
51 GFP_KERNEL);
52 if (!state)
53 return -ENOMEM;
54
55 old_n_alloc = state->n_alloc;
56 state->n_alloc = n_alloc;
57 memset(s: &state->policies[old_n_alloc], c: 0,
58 flex_array_size(state, policies, n_alloc - old_n_alloc));
59
60 state->policies[old_n_alloc].policy = policy;
61 state->policies[old_n_alloc].maxtype = maxtype;
62 *statep = state;
63
64 return 0;
65}
66
67/**
68 * netlink_policy_dump_get_policy_idx - retrieve policy index
69 * @state: the policy dump state
70 * @policy: the policy to find
71 * @maxtype: the policy's maxattr
72 *
73 * Returns: the index of the given policy in the dump state
74 *
75 * Call this to find a policy index when you've added multiple and e.g.
76 * need to tell userspace which command has which policy (by index).
77 *
78 * Note: this will WARN and return 0 if the policy isn't found, which
79 * means it wasn't added in the first place, which would be an
80 * internal consistency bug.
81 */
82int netlink_policy_dump_get_policy_idx(struct netlink_policy_dump_state *state,
83 const struct nla_policy *policy,
84 unsigned int maxtype)
85{
86 unsigned int i;
87
88 if (WARN_ON(!policy || !maxtype))
89 return 0;
90
91 for (i = 0; i < state->n_alloc; i++) {
92 if (state->policies[i].policy == policy &&
93 state->policies[i].maxtype == maxtype)
94 return i;
95 }
96
97 WARN_ON(1);
98 return 0;
99}
100
101static struct netlink_policy_dump_state *alloc_state(void)
102{
103 struct netlink_policy_dump_state *state;
104
105 state = kzalloc(struct_size(state, policies, INITIAL_POLICIES_ALLOC),
106 GFP_KERNEL);
107 if (!state)
108 return ERR_PTR(error: -ENOMEM);
109 state->n_alloc = INITIAL_POLICIES_ALLOC;
110
111 return state;
112}
113
114/**
115 * netlink_policy_dump_add_policy - add a policy to the dump
116 * @pstate: state to add to, may be reallocated, must be %NULL the first time
117 * @policy: the new policy to add to the dump
118 * @maxtype: the new policy's max attr type
119 *
120 * Returns: 0 on success, a negative error code otherwise.
121 *
122 * Call this to allocate a policy dump state, and to add policies to it. This
123 * should be called from the dump start() callback.
124 *
125 * Note: on failures, any previously allocated state is freed.
126 */
127int netlink_policy_dump_add_policy(struct netlink_policy_dump_state **pstate,
128 const struct nla_policy *policy,
129 unsigned int maxtype)
130{
131 struct netlink_policy_dump_state *state = *pstate;
132 unsigned int policy_idx;
133 int err;
134
135 if (!state) {
136 state = alloc_state();
137 if (IS_ERR(ptr: state))
138 return PTR_ERR(ptr: state);
139 }
140
141 /*
142 * walk the policies and nested ones first, and build
143 * a linear list of them.
144 */
145
146 err = add_policy(statep: &state, policy, maxtype);
147 if (err)
148 goto err_try_undo;
149
150 for (policy_idx = 0;
151 policy_idx < state->n_alloc && state->policies[policy_idx].policy;
152 policy_idx++) {
153 const struct nla_policy *policy;
154 unsigned int type;
155
156 policy = state->policies[policy_idx].policy;
157
158 for (type = 0;
159 type <= state->policies[policy_idx].maxtype;
160 type++) {
161 switch (policy[type].type) {
162 case NLA_NESTED:
163 case NLA_NESTED_ARRAY:
164 err = add_policy(statep: &state,
165 policy: policy[type].nested_policy,
166 maxtype: policy[type].len);
167 if (err)
168 goto err_try_undo;
169 break;
170 default:
171 break;
172 }
173 }
174 }
175
176 *pstate = state;
177 return 0;
178
179err_try_undo:
180 /* Try to preserve reasonable unwind semantics - if we're starting from
181 * scratch clean up fully, otherwise record what we got and caller will.
182 */
183 if (!*pstate)
184 netlink_policy_dump_free(state);
185 else
186 *pstate = state;
187 return err;
188}
189
190static bool
191netlink_policy_dump_finished(struct netlink_policy_dump_state *state)
192{
193 return state->policy_idx >= state->n_alloc ||
194 !state->policies[state->policy_idx].policy;
195}
196
197/**
198 * netlink_policy_dump_loop - dumping loop indicator
199 * @state: the policy dump state
200 *
201 * Returns: %true if the dump continues, %false otherwise
202 *
203 * Note: this frees the dump state when finishing
204 */
205bool netlink_policy_dump_loop(struct netlink_policy_dump_state *state)
206{
207 return !netlink_policy_dump_finished(state);
208}
209
210int netlink_policy_dump_attr_size_estimate(const struct nla_policy *pt)
211{
212 /* nested + type */
213 int common = 2 * nla_attr_size(payload: sizeof(u32));
214
215 switch (pt->type) {
216 case NLA_UNSPEC:
217 case NLA_REJECT:
218 /* these actually don't need any space */
219 return 0;
220 case NLA_NESTED:
221 case NLA_NESTED_ARRAY:
222 /* common, policy idx, policy maxattr */
223 return common + 2 * nla_attr_size(payload: sizeof(u32));
224 case NLA_U8:
225 case NLA_U16:
226 case NLA_U32:
227 case NLA_U64:
228 case NLA_MSECS:
229 case NLA_S8:
230 case NLA_S16:
231 case NLA_S32:
232 case NLA_S64:
233 case NLA_SINT:
234 case NLA_UINT:
235 /* maximum is common, u64 min/max with padding */
236 return common +
237 2 * (nla_attr_size(payload: 0) + nla_attr_size(payload: sizeof(u64)));
238 case NLA_BITFIELD32:
239 return common + nla_attr_size(payload: sizeof(u32));
240 case NLA_STRING:
241 case NLA_NUL_STRING:
242 case NLA_BINARY:
243 /* maximum is common, u32 min-length/max-length */
244 return common + 2 * nla_attr_size(payload: sizeof(u32));
245 case NLA_FLAG:
246 return common;
247 }
248
249 /* this should then cause a warning later */
250 return 0;
251}
252
253static int
254__netlink_policy_dump_write_attr(struct netlink_policy_dump_state *state,
255 struct sk_buff *skb,
256 const struct nla_policy *pt,
257 int nestattr)
258{
259 int estimate = netlink_policy_dump_attr_size_estimate(pt);
260 enum netlink_attribute_type type;
261 struct nlattr *attr;
262
263 attr = nla_nest_start(skb, attrtype: nestattr);
264 if (!attr)
265 return -ENOBUFS;
266
267 switch (pt->type) {
268 default:
269 case NLA_UNSPEC:
270 case NLA_REJECT:
271 /* skip - use NLA_MIN_LEN to advertise such */
272 nla_nest_cancel(skb, start: attr);
273 return -ENODATA;
274 case NLA_NESTED:
275 type = NL_ATTR_TYPE_NESTED;
276 fallthrough;
277 case NLA_NESTED_ARRAY:
278 if (pt->type == NLA_NESTED_ARRAY)
279 type = NL_ATTR_TYPE_NESTED_ARRAY;
280 if (state && pt->nested_policy && pt->len &&
281 (nla_put_u32(skb, attrtype: NL_POLICY_TYPE_ATTR_POLICY_IDX,
282 value: netlink_policy_dump_get_policy_idx(state,
283 policy: pt->nested_policy,
284 maxtype: pt->len)) ||
285 nla_put_u32(skb, attrtype: NL_POLICY_TYPE_ATTR_POLICY_MAXTYPE,
286 value: pt->len)))
287 goto nla_put_failure;
288 break;
289 case NLA_U8:
290 case NLA_U16:
291 case NLA_U32:
292 case NLA_U64:
293 case NLA_UINT:
294 case NLA_MSECS: {
295 struct netlink_range_validation range;
296
297 if (pt->type == NLA_U8)
298 type = NL_ATTR_TYPE_U8;
299 else if (pt->type == NLA_U16)
300 type = NL_ATTR_TYPE_U16;
301 else if (pt->type == NLA_U32)
302 type = NL_ATTR_TYPE_U32;
303 else if (pt->type == NLA_U64)
304 type = NL_ATTR_TYPE_U64;
305 else
306 type = NL_ATTR_TYPE_UINT;
307
308 if (pt->validation_type == NLA_VALIDATE_MASK) {
309 if (nla_put_u64_64bit(skb, attrtype: NL_POLICY_TYPE_ATTR_MASK,
310 value: pt->mask,
311 padattr: NL_POLICY_TYPE_ATTR_PAD))
312 goto nla_put_failure;
313 break;
314 } else if (pt->validation_type == NLA_VALIDATE_FUNCTION) {
315 break;
316 }
317
318 nla_get_range_unsigned(pt, range: &range);
319
320 if (nla_put_u64_64bit(skb, attrtype: NL_POLICY_TYPE_ATTR_MIN_VALUE_U,
321 value: range.min, padattr: NL_POLICY_TYPE_ATTR_PAD) ||
322 nla_put_u64_64bit(skb, attrtype: NL_POLICY_TYPE_ATTR_MAX_VALUE_U,
323 value: range.max, padattr: NL_POLICY_TYPE_ATTR_PAD))
324 goto nla_put_failure;
325 break;
326 }
327 case NLA_S8:
328 case NLA_S16:
329 case NLA_S32:
330 case NLA_S64:
331 case NLA_SINT: {
332 struct netlink_range_validation_signed range;
333
334 if (pt->type == NLA_S8)
335 type = NL_ATTR_TYPE_S8;
336 else if (pt->type == NLA_S16)
337 type = NL_ATTR_TYPE_S16;
338 else if (pt->type == NLA_S32)
339 type = NL_ATTR_TYPE_S32;
340 else if (pt->type == NLA_S64)
341 type = NL_ATTR_TYPE_S64;
342 else
343 type = NL_ATTR_TYPE_SINT;
344
345 if (pt->validation_type == NLA_VALIDATE_FUNCTION)
346 break;
347
348 nla_get_range_signed(pt, range: &range);
349
350 if (nla_put_s64(skb, attrtype: NL_POLICY_TYPE_ATTR_MIN_VALUE_S,
351 value: range.min, padattr: NL_POLICY_TYPE_ATTR_PAD) ||
352 nla_put_s64(skb, attrtype: NL_POLICY_TYPE_ATTR_MAX_VALUE_S,
353 value: range.max, padattr: NL_POLICY_TYPE_ATTR_PAD))
354 goto nla_put_failure;
355 break;
356 }
357 case NLA_BITFIELD32:
358 type = NL_ATTR_TYPE_BITFIELD32;
359 if (nla_put_u32(skb, attrtype: NL_POLICY_TYPE_ATTR_BITFIELD32_MASK,
360 value: pt->bitfield32_valid))
361 goto nla_put_failure;
362 break;
363 case NLA_STRING:
364 case NLA_NUL_STRING:
365 case NLA_BINARY:
366 if (pt->type == NLA_STRING)
367 type = NL_ATTR_TYPE_STRING;
368 else if (pt->type == NLA_NUL_STRING)
369 type = NL_ATTR_TYPE_NUL_STRING;
370 else
371 type = NL_ATTR_TYPE_BINARY;
372
373 if (pt->validation_type == NLA_VALIDATE_RANGE ||
374 pt->validation_type == NLA_VALIDATE_RANGE_WARN_TOO_LONG) {
375 struct netlink_range_validation range;
376
377 nla_get_range_unsigned(pt, range: &range);
378
379 if (range.min &&
380 nla_put_u32(skb, attrtype: NL_POLICY_TYPE_ATTR_MIN_LENGTH,
381 value: range.min))
382 goto nla_put_failure;
383
384 if (range.max < U16_MAX &&
385 nla_put_u32(skb, attrtype: NL_POLICY_TYPE_ATTR_MAX_LENGTH,
386 value: range.max))
387 goto nla_put_failure;
388 } else if (pt->len &&
389 nla_put_u32(skb, attrtype: NL_POLICY_TYPE_ATTR_MAX_LENGTH,
390 value: pt->len)) {
391 goto nla_put_failure;
392 }
393 break;
394 case NLA_FLAG:
395 type = NL_ATTR_TYPE_FLAG;
396 break;
397 }
398
399 if (nla_put_u32(skb, attrtype: NL_POLICY_TYPE_ATTR_TYPE, value: type))
400 goto nla_put_failure;
401
402 nla_nest_end(skb, start: attr);
403 WARN_ON(attr->nla_len > estimate);
404
405 return 0;
406nla_put_failure:
407 nla_nest_cancel(skb, start: attr);
408 return -ENOBUFS;
409}
410
411/**
412 * netlink_policy_dump_write_attr - write a given attribute policy
413 * @skb: the message skb to write to
414 * @pt: the attribute's policy
415 * @nestattr: the nested attribute ID to use
416 *
417 * Returns: 0 on success, an error code otherwise; -%ENODATA is
418 * special, indicating that there's no policy data and
419 * the attribute is generally rejected.
420 */
421int netlink_policy_dump_write_attr(struct sk_buff *skb,
422 const struct nla_policy *pt,
423 int nestattr)
424{
425 return __netlink_policy_dump_write_attr(NULL, skb, pt, nestattr);
426}
427
428/**
429 * netlink_policy_dump_write - write current policy dump attributes
430 * @skb: the message skb to write to
431 * @state: the policy dump state
432 *
433 * Returns: 0 on success, an error code otherwise
434 */
435int netlink_policy_dump_write(struct sk_buff *skb,
436 struct netlink_policy_dump_state *state)
437{
438 const struct nla_policy *pt;
439 struct nlattr *policy;
440 bool again;
441 int err;
442
443send_attribute:
444 again = false;
445
446 pt = &state->policies[state->policy_idx].policy[state->attr_idx];
447
448 policy = nla_nest_start(skb, attrtype: state->policy_idx);
449 if (!policy)
450 return -ENOBUFS;
451
452 err = __netlink_policy_dump_write_attr(state, skb, pt, nestattr: state->attr_idx);
453 if (err == -ENODATA) {
454 nla_nest_cancel(skb, start: policy);
455 again = true;
456 goto next;
457 } else if (err) {
458 goto nla_put_failure;
459 }
460
461 /* finish and move state to next attribute */
462 nla_nest_end(skb, start: policy);
463
464next:
465 state->attr_idx += 1;
466 if (state->attr_idx > state->policies[state->policy_idx].maxtype) {
467 state->attr_idx = 0;
468 state->policy_idx++;
469 }
470
471 if (again) {
472 if (netlink_policy_dump_finished(state))
473 return -ENODATA;
474 goto send_attribute;
475 }
476
477 return 0;
478
479nla_put_failure:
480 nla_nest_cancel(skb, start: policy);
481 return -ENOBUFS;
482}
483
484/**
485 * netlink_policy_dump_free - free policy dump state
486 * @state: the policy dump state to free
487 *
488 * Call this from the done() method to ensure dump state is freed.
489 */
490void netlink_policy_dump_free(struct netlink_policy_dump_state *state)
491{
492 kfree(objp: state);
493}
494