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 
16 static 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  */
__lookup_constant(const struct constant_table * tbl,size_t tbl_size,const char * name,int not_found)32 int __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 }
43 EXPORT_SYMBOL(__lookup_constant);
44 
fs_lookup_key(const struct fs_parameter_description * desc,const char * name)45 static 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  */
fs_parse(struct fs_context * fc,const struct fs_parameter_description * desc,struct fs_parameter * param,struct fs_parse_result * result)79 int 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 
233 maybe_okay:
234 	if (ret < 0)
235 		goto bad_value;
236 okay:
237 	return p->opt;
238 
239 bad_value:
240 	return invalf(fc, "%s: Bad value for '%s'", desc->name, param->key);
241 unknown_parameter:
242 	return -ENOPARAM;
243 }
244 EXPORT_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  */
fs_lookup_param(struct fs_context * fc,struct fs_parameter * param,bool want_bdev,struct path * _path)253 int 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 
298 out:
299 	if (put_f)
300 		putname(f);
301 	return ret;
302 }
303 EXPORT_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  */
validate_constant_table(const struct constant_table * tbl,size_t tbl_size,int low,int high,int special)315 bool 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  */
fs_validate_description(const struct fs_parameter_description * desc)360 bool 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 
455 no_enums:
456 	return good;
457 }
458 #endif /* CONFIG_VALIDATE_FS_PARSER */
459