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1// SPDX-License-Identifier: GPL-2.0-or-later
2/* Filesystem parameter parser.
3 *
4 * Copyright (C) 2018 Red Hat, Inc. All Rights Reserved.
5 * Written by David Howells (dhowells@redhat.com)
6 */
7
8#include <linux/export.h>
9#include <linux/fs_context.h>
10#include <linux/fs_parser.h>
11#include <linux/slab.h>
12#include <linux/security.h>
13#include <linux/namei.h>
14#include "internal.h"
15
16static const struct constant_table bool_names[] = {
17 { "0", false },
18 { "1", true },
19 { "false", false },
20 { "no", false },
21 { "true", true },
22 { "yes", true },
23};
24
25/**
26 * lookup_constant - Look up a constant by name in an ordered table
27 * @tbl: The table of constants to search.
28 * @tbl_size: The size of the table.
29 * @name: The name to look up.
30 * @not_found: The value to return if the name is not found.
31 */
32int __lookup_constant(const struct constant_table *tbl, size_t tbl_size,
33 const char *name, int not_found)
34{
35 unsigned int i;
36
37 for (i = 0; i < tbl_size; i++)
38 if (strcmp(name, tbl[i].name) == 0)
39 return tbl[i].value;
40
41 return not_found;
42}
43EXPORT_SYMBOL(__lookup_constant);
44
45static const struct fs_parameter_spec *fs_lookup_key(
46 const struct fs_parameter_description *desc,
47 const char *name)
48{
49 const struct fs_parameter_spec *p;
50
51 if (!desc->specs)
52 return NULL;
53
54 for (p = desc->specs; p->name; p++)
55 if (strcmp(p->name, name) == 0)
56 return p;
57
58 return NULL;
59}
60
61/*
62 * fs_parse - Parse a filesystem configuration parameter
63 * @fc: The filesystem context to log errors through.
64 * @desc: The parameter description to use.
65 * @param: The parameter.
66 * @result: Where to place the result of the parse
67 *
68 * Parse a filesystem configuration parameter and attempt a conversion for a
69 * simple parameter for which this is requested. If successful, the determined
70 * parameter ID is placed into @result->key, the desired type is indicated in
71 * @result->t and any converted value is placed into an appropriate member of
72 * the union in @result.
73 *
74 * The function returns the parameter number if the parameter was matched,
75 * -ENOPARAM if it wasn't matched and @desc->ignore_unknown indicated that
76 * unknown parameters are okay and -EINVAL if there was a conversion issue or
77 * the parameter wasn't recognised and unknowns aren't okay.
78 */
79int fs_parse(struct fs_context *fc,
80 const struct fs_parameter_description *desc,
81 struct fs_parameter *param,
82 struct fs_parse_result *result)
83{
84 const struct fs_parameter_spec *p;
85 const struct fs_parameter_enum *e;
86 int ret = -ENOPARAM, b;
87
88 result->has_value = !!param->string;
89 result->negated = false;
90 result->uint_64 = 0;
91
92 p = fs_lookup_key(desc, param->key);
93 if (!p) {
94 /* If we didn't find something that looks like "noxxx", see if
95 * "xxx" takes the "no"-form negative - but only if there
96 * wasn't an value.
97 */
98 if (result->has_value)
99 goto unknown_parameter;
100 if (param->key[0] != 'n' || param->key[1] != 'o' || !param->key[2])
101 goto unknown_parameter;
102
103 p = fs_lookup_key(desc, param->key + 2);
104 if (!p)
105 goto unknown_parameter;
106 if (!(p->flags & fs_param_neg_with_no))
107 goto unknown_parameter;
108 result->boolean = false;
109 result->negated = true;
110 }
111
112 if (p->flags & fs_param_deprecated)
113 warnf(fc, "%s: Deprecated parameter '%s'",
114 desc->name, param->key);
115
116 if (result->negated)
117 goto okay;
118
119 /* Certain parameter types only take a string and convert it. */
120 switch (p->type) {
121 case __fs_param_wasnt_defined:
122 return -EINVAL;
123 case fs_param_is_u32:
124 case fs_param_is_u32_octal:
125 case fs_param_is_u32_hex:
126 case fs_param_is_s32:
127 case fs_param_is_u64:
128 case fs_param_is_enum:
129 case fs_param_is_string:
130 if (param->type != fs_value_is_string)
131 goto bad_value;
132 if (!result->has_value) {
133 if (p->flags & fs_param_v_optional)
134 goto okay;
135 goto bad_value;
136 }
137 /* Fall through */
138 default:
139 break;
140 }
141
142 /* Try to turn the type we were given into the type desired by the
143 * parameter and give an error if we can't.
144 */
145 switch (p->type) {
146 case fs_param_is_flag:
147 if (param->type != fs_value_is_flag &&
148 (param->type != fs_value_is_string || result->has_value))
149 return invalf(fc, "%s: Unexpected value for '%s'",
150 desc->name, param->key);
151 result->boolean = true;
152 goto okay;
153
154 case fs_param_is_bool:
155 switch (param->type) {
156 case fs_value_is_flag:
157 result->boolean = true;
158 goto okay;
159 case fs_value_is_string:
160 if (param->size == 0) {
161 result->boolean = true;
162 goto okay;
163 }
164 b = lookup_constant(bool_names, param->string, -1);
165 if (b == -1)
166 goto bad_value;
167 result->boolean = b;
168 goto okay;
169 default:
170 goto bad_value;
171 }
172
173 case fs_param_is_u32:
174 ret = kstrtouint(param->string, 0, &result->uint_32);
175 goto maybe_okay;
176 case fs_param_is_u32_octal:
177 ret = kstrtouint(param->string, 8, &result->uint_32);
178 goto maybe_okay;
179 case fs_param_is_u32_hex:
180 ret = kstrtouint(param->string, 16, &result->uint_32);
181 goto maybe_okay;
182 case fs_param_is_s32:
183 ret = kstrtoint(param->string, 0, &result->int_32);
184 goto maybe_okay;
185 case fs_param_is_u64:
186 ret = kstrtoull(param->string, 0, &result->uint_64);
187 goto maybe_okay;
188
189 case fs_param_is_enum:
190 for (e = desc->enums; e->name[0]; e++) {
191 if (e->opt == p->opt &&
192 strcmp(e->name, param->string) == 0) {
193 result->uint_32 = e->value;
194 goto okay;
195 }
196 }
197 goto bad_value;
198
199 case fs_param_is_string:
200 goto okay;
201 case fs_param_is_blob:
202 if (param->type != fs_value_is_blob)
203 goto bad_value;
204 goto okay;
205
206 case fs_param_is_fd: {
207 switch (param->type) {
208 case fs_value_is_string:
209 if (!result->has_value)
210 goto bad_value;
211
212 ret = kstrtouint(param->string, 0, &result->uint_32);
213 break;
214 case fs_value_is_file:
215 result->uint_32 = param->dirfd;
216 ret = 0;
217 default:
218 goto bad_value;
219 }
220
221 if (result->uint_32 > INT_MAX)
222 goto bad_value;
223 goto maybe_okay;
224 }
225
226 case fs_param_is_blockdev:
227 case fs_param_is_path:
228 goto okay;
229 default:
230 BUG();
231 }
232
233maybe_okay:
234 if (ret < 0)
235 goto bad_value;
236okay:
237 return p->opt;
238
239bad_value:
240 return invalf(fc, "%s: Bad value for '%s'", desc->name, param->key);
241unknown_parameter:
242 return -ENOPARAM;
243}
244EXPORT_SYMBOL(fs_parse);
245
246/**
247 * fs_lookup_param - Look up a path referred to by a parameter
248 * @fc: The filesystem context to log errors through.
249 * @param: The parameter.
250 * @want_bdev: T if want a blockdev
251 * @_path: The result of the lookup
252 */
253int fs_lookup_param(struct fs_context *fc,
254 struct fs_parameter *param,
255 bool want_bdev,
256 struct path *_path)
257{
258 struct filename *f;
259 unsigned int flags = 0;
260 bool put_f;
261 int ret;
262
263 switch (param->type) {
264 case fs_value_is_string:
265 f = getname_kernel(param->string);
266 if (IS_ERR(f))
267 return PTR_ERR(f);
268 put_f = true;
269 break;
270 case fs_value_is_filename_empty:
271 flags = LOOKUP_EMPTY;
272 /* Fall through */
273 case fs_value_is_filename:
274 f = param->name;
275 put_f = false;
276 break;
277 default:
278 return invalf(fc, "%s: not usable as path", param->key);
279 }
280
281 f->refcnt++; /* filename_lookup() drops our ref. */
282 ret = filename_lookup(param->dirfd, f, flags, _path, NULL);
283 if (ret < 0) {
284 errorf(fc, "%s: Lookup failure for '%s'", param->key, f->name);
285 goto out;
286 }
287
288 if (want_bdev &&
289 !S_ISBLK(d_backing_inode(_path->dentry)->i_mode)) {
290 path_put(_path);
291 _path->dentry = NULL;
292 _path->mnt = NULL;
293 errorf(fc, "%s: Non-blockdev passed as '%s'",
294 param->key, f->name);
295 ret = -ENOTBLK;
296 }
297
298out:
299 if (put_f)
300 putname(f);
301 return ret;
302}
303EXPORT_SYMBOL(fs_lookup_param);
304
305#ifdef CONFIG_VALIDATE_FS_PARSER
306/**
307 * validate_constant_table - Validate a constant table
308 * @name: Name to use in reporting
309 * @tbl: The constant table to validate.
310 * @tbl_size: The size of the table.
311 * @low: The lowest permissible value.
312 * @high: The highest permissible value.
313 * @special: One special permissible value outside of the range.
314 */
315bool validate_constant_table(const struct constant_table *tbl, size_t tbl_size,
316 int low, int high, int special)
317{
318 size_t i;
319 bool good = true;
320
321 if (tbl_size == 0) {
322 pr_warn("VALIDATE C-TBL: Empty\n");
323 return true;
324 }
325
326 for (i = 0; i < tbl_size; i++) {
327 if (!tbl[i].name) {
328 pr_err("VALIDATE C-TBL[%zu]: Null\n", i);
329 good = false;
330 } else if (i > 0 && tbl[i - 1].name) {
331 int c = strcmp(tbl[i-1].name, tbl[i].name);
332
333 if (c == 0) {
334 pr_err("VALIDATE C-TBL[%zu]: Duplicate %s\n",
335 i, tbl[i].name);
336 good = false;
337 }
338 if (c > 0) {
339 pr_err("VALIDATE C-TBL[%zu]: Missorted %s>=%s\n",
340 i, tbl[i-1].name, tbl[i].name);
341 good = false;
342 }
343 }
344
345 if (tbl[i].value != special &&
346 (tbl[i].value < low || tbl[i].value > high)) {
347 pr_err("VALIDATE C-TBL[%zu]: %s->%d const out of range (%d-%d)\n",
348 i, tbl[i].name, tbl[i].value, low, high);
349 good = false;
350 }
351 }
352
353 return good;
354}
355
356/**
357 * fs_validate_description - Validate a parameter description
358 * @desc: The parameter description to validate.
359 */
360bool fs_validate_description(const struct fs_parameter_description *desc)
361{
362 const struct fs_parameter_spec *param, *p2;
363 const struct fs_parameter_enum *e;
364 const char *name = desc->name;
365 unsigned int nr_params = 0;
366 bool good = true, enums = false;
367
368 pr_notice("*** VALIDATE %s ***\n", name);
369
370 if (!name[0]) {
371 pr_err("VALIDATE Parser: No name\n");
372 name = "Unknown";
373 good = false;
374 }
375
376 if (desc->specs) {
377 for (param = desc->specs; param->name; param++) {
378 enum fs_parameter_type t = param->type;
379
380 /* Check that the type is in range */
381 if (t == __fs_param_wasnt_defined ||
382 t >= nr__fs_parameter_type) {
383 pr_err("VALIDATE %s: PARAM[%s] Bad type %u\n",
384 name, param->name, t);
385 good = false;
386 } else if (t == fs_param_is_enum) {
387 enums = true;
388 }
389
390 /* Check for duplicate parameter names */
391 for (p2 = desc->specs; p2 < param; p2++) {
392 if (strcmp(param->name, p2->name) == 0) {
393 pr_err("VALIDATE %s: PARAM[%s]: Duplicate\n",
394 name, param->name);
395 good = false;
396 }
397 }
398 }
399
400 nr_params = param - desc->specs;
401 }
402
403 if (desc->enums) {
404 if (!nr_params) {
405 pr_err("VALIDATE %s: Enum table but no parameters\n",
406 name);
407 good = false;
408 goto no_enums;
409 }
410 if (!enums) {
411 pr_err("VALIDATE %s: Enum table but no enum-type values\n",
412 name);
413 good = false;
414 goto no_enums;
415 }
416
417 for (e = desc->enums; e->name[0]; e++) {
418 /* Check that all entries in the enum table have at
419 * least one parameter that uses them.
420 */
421 for (param = desc->specs; param->name; param++) {
422 if (param->opt == e->opt &&
423 param->type != fs_param_is_enum) {
424 pr_err("VALIDATE %s: e[%tu] enum val for %s\n",
425 name, e - desc->enums, param->name);
426 good = false;
427 }
428 }
429 }
430
431 /* Check that all enum-type parameters have at least one enum
432 * value in the enum table.
433 */
434 for (param = desc->specs; param->name; param++) {
435 if (param->type != fs_param_is_enum)
436 continue;
437 for (e = desc->enums; e->name[0]; e++)
438 if (e->opt == param->opt)
439 break;
440 if (!e->name[0]) {
441 pr_err("VALIDATE %s: PARAM[%s] enum with no values\n",
442 name, param->name);
443 good = false;
444 }
445 }
446 } else {
447 if (enums) {
448 pr_err("VALIDATE %s: enum-type values, but no enum table\n",
449 name);
450 good = false;
451 goto no_enums;
452 }
453 }
454
455no_enums:
456 return good;
457}
458#endif /* CONFIG_VALIDATE_FS_PARSER */