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 static const struct constant_table *
__lookup_constant(const struct constant_table * tbl,const char * name)27 __lookup_constant(const struct constant_table *tbl, const char *name)
28 {
29 	for ( ; tbl->name; tbl++)
30 		if (strcmp(name, tbl->name) == 0)
31 			return tbl;
32 	return NULL;
33 }
34 
35 /**
36  * lookup_constant - Look up a constant by name in an ordered table
37  * @tbl: The table of constants to search.
38  * @name: The name to look up.
39  * @not_found: The value to return if the name is not found.
40  */
lookup_constant(const struct constant_table * tbl,const char * name,int not_found)41 int lookup_constant(const struct constant_table *tbl, const char *name, int not_found)
42 {
43 	const struct constant_table *p = __lookup_constant(tbl, name);
44 
45 	return p ? p->value : not_found;
46 }
47 EXPORT_SYMBOL(lookup_constant);
48 
is_flag(const struct fs_parameter_spec * p)49 static inline bool is_flag(const struct fs_parameter_spec *p)
50 {
51 	return p->type == NULL;
52 }
53 
fs_lookup_key(const struct fs_parameter_spec * desc,struct fs_parameter * param,bool * negated)54 static const struct fs_parameter_spec *fs_lookup_key(
55 	const struct fs_parameter_spec *desc,
56 	struct fs_parameter *param, bool *negated)
57 {
58 	const struct fs_parameter_spec *p, *other = NULL;
59 	const char *name = param->key;
60 	bool want_flag = param->type == fs_value_is_flag;
61 
62 	*negated = false;
63 	for (p = desc; p->name; p++) {
64 		if (strcmp(p->name, name) != 0)
65 			continue;
66 		if (likely(is_flag(p) == want_flag))
67 			return p;
68 		other = p;
69 	}
70 	if (want_flag) {
71 		if (name[0] == 'n' && name[1] == 'o' && name[2]) {
72 			for (p = desc; p->name; p++) {
73 				if (strcmp(p->name, name + 2) != 0)
74 					continue;
75 				if (!(p->flags & fs_param_neg_with_no))
76 					continue;
77 				*negated = true;
78 				return p;
79 			}
80 		}
81 	}
82 	return other;
83 }
84 
85 /*
86  * fs_parse - Parse a filesystem configuration parameter
87  * @fc: The filesystem context to log errors through.
88  * @desc: The parameter description to use.
89  * @param: The parameter.
90  * @result: Where to place the result of the parse
91  *
92  * Parse a filesystem configuration parameter and attempt a conversion for a
93  * simple parameter for which this is requested.  If successful, the determined
94  * parameter ID is placed into @result->key, the desired type is indicated in
95  * @result->t and any converted value is placed into an appropriate member of
96  * the union in @result.
97  *
98  * The function returns the parameter number if the parameter was matched,
99  * -ENOPARAM if it wasn't matched and @desc->ignore_unknown indicated that
100  * unknown parameters are okay and -EINVAL if there was a conversion issue or
101  * the parameter wasn't recognised and unknowns aren't okay.
102  */
__fs_parse(struct p_log * log,const struct fs_parameter_spec * desc,struct fs_parameter * param,struct fs_parse_result * result)103 int __fs_parse(struct p_log *log,
104 	     const struct fs_parameter_spec *desc,
105 	     struct fs_parameter *param,
106 	     struct fs_parse_result *result)
107 {
108 	const struct fs_parameter_spec *p;
109 
110 	result->uint_64 = 0;
111 
112 	p = fs_lookup_key(desc, param, &result->negated);
113 	if (!p)
114 		return -ENOPARAM;
115 
116 	if (p->flags & fs_param_deprecated)
117 		warn_plog(log, "Deprecated parameter '%s'", param->key);
118 
119 	/* Try to turn the type we were given into the type desired by the
120 	 * parameter and give an error if we can't.
121 	 */
122 	if (is_flag(p)) {
123 		if (param->type != fs_value_is_flag)
124 			return inval_plog(log, "Unexpected value for '%s'",
125 				      param->key);
126 		result->boolean = !result->negated;
127 	} else  {
128 		int ret = p->type(log, p, param, result);
129 		if (ret)
130 			return ret;
131 	}
132 	return p->opt;
133 }
134 EXPORT_SYMBOL(__fs_parse);
135 
136 /**
137  * fs_lookup_param - Look up a path referred to by a parameter
138  * @fc: The filesystem context to log errors through.
139  * @param: The parameter.
140  * @want_bdev: T if want a blockdev
141  * @flags: Pathwalk flags passed to filename_lookup()
142  * @_path: The result of the lookup
143  */
fs_lookup_param(struct fs_context * fc,struct fs_parameter * param,bool want_bdev,unsigned int flags,struct path * _path)144 int fs_lookup_param(struct fs_context *fc,
145 		    struct fs_parameter *param,
146 		    bool want_bdev,
147 		    unsigned int flags,
148 		    struct path *_path)
149 {
150 	struct filename *f;
151 	bool put_f;
152 	int ret;
153 
154 	switch (param->type) {
155 	case fs_value_is_string:
156 		f = getname_kernel(param->string);
157 		if (IS_ERR(f))
158 			return PTR_ERR(f);
159 		put_f = true;
160 		break;
161 	case fs_value_is_filename:
162 		f = param->name;
163 		put_f = false;
164 		break;
165 	default:
166 		return invalf(fc, "%s: not usable as path", param->key);
167 	}
168 
169 	ret = filename_lookup(param->dirfd, f, flags, _path, NULL);
170 	if (ret < 0) {
171 		errorf(fc, "%s: Lookup failure for '%s'", param->key, f->name);
172 		goto out;
173 	}
174 
175 	if (want_bdev &&
176 	    !S_ISBLK(d_backing_inode(_path->dentry)->i_mode)) {
177 		path_put(_path);
178 		_path->dentry = NULL;
179 		_path->mnt = NULL;
180 		errorf(fc, "%s: Non-blockdev passed as '%s'",
181 		       param->key, f->name);
182 		ret = -ENOTBLK;
183 	}
184 
185 out:
186 	if (put_f)
187 		putname(f);
188 	return ret;
189 }
190 EXPORT_SYMBOL(fs_lookup_param);
191 
fs_param_bad_value(struct p_log * log,struct fs_parameter * param)192 static int fs_param_bad_value(struct p_log *log, struct fs_parameter *param)
193 {
194 	return inval_plog(log, "Bad value for '%s'", param->key);
195 }
196 
fs_param_is_bool(struct p_log * log,const struct fs_parameter_spec * p,struct fs_parameter * param,struct fs_parse_result * result)197 int fs_param_is_bool(struct p_log *log, const struct fs_parameter_spec *p,
198 		     struct fs_parameter *param, struct fs_parse_result *result)
199 {
200 	int b;
201 	if (param->type != fs_value_is_string)
202 		return fs_param_bad_value(log, param);
203 	if (!*param->string && (p->flags & fs_param_can_be_empty))
204 		return 0;
205 	b = lookup_constant(bool_names, param->string, -1);
206 	if (b == -1)
207 		return fs_param_bad_value(log, param);
208 	result->boolean = b;
209 	return 0;
210 }
211 EXPORT_SYMBOL(fs_param_is_bool);
212 
fs_param_is_u32(struct p_log * log,const struct fs_parameter_spec * p,struct fs_parameter * param,struct fs_parse_result * result)213 int fs_param_is_u32(struct p_log *log, const struct fs_parameter_spec *p,
214 		    struct fs_parameter *param, struct fs_parse_result *result)
215 {
216 	int base = (unsigned long)p->data;
217 	if (param->type != fs_value_is_string)
218 		return fs_param_bad_value(log, param);
219 	if (!*param->string && (p->flags & fs_param_can_be_empty))
220 		return 0;
221 	if (kstrtouint(param->string, base, &result->uint_32) < 0)
222 		return fs_param_bad_value(log, param);
223 	return 0;
224 }
225 EXPORT_SYMBOL(fs_param_is_u32);
226 
fs_param_is_s32(struct p_log * log,const struct fs_parameter_spec * p,struct fs_parameter * param,struct fs_parse_result * result)227 int fs_param_is_s32(struct p_log *log, const struct fs_parameter_spec *p,
228 		    struct fs_parameter *param, struct fs_parse_result *result)
229 {
230 	if (param->type != fs_value_is_string)
231 		return fs_param_bad_value(log, param);
232 	if (!*param->string && (p->flags & fs_param_can_be_empty))
233 		return 0;
234 	if (kstrtoint(param->string, 0, &result->int_32) < 0)
235 		return fs_param_bad_value(log, param);
236 	return 0;
237 }
238 EXPORT_SYMBOL(fs_param_is_s32);
239 
fs_param_is_u64(struct p_log * log,const struct fs_parameter_spec * p,struct fs_parameter * param,struct fs_parse_result * result)240 int fs_param_is_u64(struct p_log *log, const struct fs_parameter_spec *p,
241 		    struct fs_parameter *param, struct fs_parse_result *result)
242 {
243 	if (param->type != fs_value_is_string)
244 		return fs_param_bad_value(log, param);
245 	if (!*param->string && (p->flags & fs_param_can_be_empty))
246 		return 0;
247 	if (kstrtoull(param->string, 0, &result->uint_64) < 0)
248 		return fs_param_bad_value(log, param);
249 	return 0;
250 }
251 EXPORT_SYMBOL(fs_param_is_u64);
252 
fs_param_is_enum(struct p_log * log,const struct fs_parameter_spec * p,struct fs_parameter * param,struct fs_parse_result * result)253 int fs_param_is_enum(struct p_log *log, const struct fs_parameter_spec *p,
254 		     struct fs_parameter *param, struct fs_parse_result *result)
255 {
256 	const struct constant_table *c;
257 	if (param->type != fs_value_is_string)
258 		return fs_param_bad_value(log, param);
259 	if (!*param->string && (p->flags & fs_param_can_be_empty))
260 		return 0;
261 	c = __lookup_constant(p->data, param->string);
262 	if (!c)
263 		return fs_param_bad_value(log, param);
264 	result->uint_32 = c->value;
265 	return 0;
266 }
267 EXPORT_SYMBOL(fs_param_is_enum);
268 
fs_param_is_string(struct p_log * log,const struct fs_parameter_spec * p,struct fs_parameter * param,struct fs_parse_result * result)269 int fs_param_is_string(struct p_log *log, const struct fs_parameter_spec *p,
270 		       struct fs_parameter *param, struct fs_parse_result *result)
271 {
272 	if (param->type != fs_value_is_string ||
273 	    (!*param->string && !(p->flags & fs_param_can_be_empty)))
274 		return fs_param_bad_value(log, param);
275 	return 0;
276 }
277 EXPORT_SYMBOL(fs_param_is_string);
278 
fs_param_is_blob(struct p_log * log,const struct fs_parameter_spec * p,struct fs_parameter * param,struct fs_parse_result * result)279 int fs_param_is_blob(struct p_log *log, const struct fs_parameter_spec *p,
280 		     struct fs_parameter *param, struct fs_parse_result *result)
281 {
282 	if (param->type != fs_value_is_blob)
283 		return fs_param_bad_value(log, param);
284 	return 0;
285 }
286 EXPORT_SYMBOL(fs_param_is_blob);
287 
fs_param_is_fd(struct p_log * log,const struct fs_parameter_spec * p,struct fs_parameter * param,struct fs_parse_result * result)288 int fs_param_is_fd(struct p_log *log, const struct fs_parameter_spec *p,
289 		  struct fs_parameter *param, struct fs_parse_result *result)
290 {
291 	switch (param->type) {
292 	case fs_value_is_string:
293 		if ((!*param->string && !(p->flags & fs_param_can_be_empty)) ||
294 		    kstrtouint(param->string, 0, &result->uint_32) < 0)
295 			break;
296 		if (result->uint_32 <= INT_MAX)
297 			return 0;
298 		break;
299 	case fs_value_is_file:
300 		result->uint_32 = param->dirfd;
301 		if (result->uint_32 <= INT_MAX)
302 			return 0;
303 		break;
304 	default:
305 		break;
306 	}
307 	return fs_param_bad_value(log, param);
308 }
309 EXPORT_SYMBOL(fs_param_is_fd);
310 
fs_param_is_blockdev(struct p_log * log,const struct fs_parameter_spec * p,struct fs_parameter * param,struct fs_parse_result * result)311 int fs_param_is_blockdev(struct p_log *log, const struct fs_parameter_spec *p,
312 		  struct fs_parameter *param, struct fs_parse_result *result)
313 {
314 	return 0;
315 }
316 EXPORT_SYMBOL(fs_param_is_blockdev);
317 
fs_param_is_path(struct p_log * log,const struct fs_parameter_spec * p,struct fs_parameter * param,struct fs_parse_result * result)318 int fs_param_is_path(struct p_log *log, const struct fs_parameter_spec *p,
319 		     struct fs_parameter *param, struct fs_parse_result *result)
320 {
321 	return 0;
322 }
323 EXPORT_SYMBOL(fs_param_is_path);
324 
325 #ifdef CONFIG_VALIDATE_FS_PARSER
326 /**
327  * validate_constant_table - Validate a constant table
328  * @tbl: The constant table to validate.
329  * @tbl_size: The size of the table.
330  * @low: The lowest permissible value.
331  * @high: The highest permissible value.
332  * @special: One special permissible value outside of the range.
333  */
validate_constant_table(const struct constant_table * tbl,size_t tbl_size,int low,int high,int special)334 bool validate_constant_table(const struct constant_table *tbl, size_t tbl_size,
335 			     int low, int high, int special)
336 {
337 	size_t i;
338 	bool good = true;
339 
340 	if (tbl_size == 0) {
341 		pr_warn("VALIDATE C-TBL: Empty\n");
342 		return true;
343 	}
344 
345 	for (i = 0; i < tbl_size; i++) {
346 		if (!tbl[i].name) {
347 			pr_err("VALIDATE C-TBL[%zu]: Null\n", i);
348 			good = false;
349 		} else if (i > 0 && tbl[i - 1].name) {
350 			int c = strcmp(tbl[i-1].name, tbl[i].name);
351 
352 			if (c == 0) {
353 				pr_err("VALIDATE C-TBL[%zu]: Duplicate %s\n",
354 				       i, tbl[i].name);
355 				good = false;
356 			}
357 			if (c > 0) {
358 				pr_err("VALIDATE C-TBL[%zu]: Missorted %s>=%s\n",
359 				       i, tbl[i-1].name, tbl[i].name);
360 				good = false;
361 			}
362 		}
363 
364 		if (tbl[i].value != special &&
365 		    (tbl[i].value < low || tbl[i].value > high)) {
366 			pr_err("VALIDATE C-TBL[%zu]: %s->%d const out of range (%d-%d)\n",
367 			       i, tbl[i].name, tbl[i].value, low, high);
368 			good = false;
369 		}
370 	}
371 
372 	return good;
373 }
374 
375 /**
376  * fs_validate_description - Validate a parameter description
377  * @name: The parameter name to search for.
378  * @desc: The parameter description to validate.
379  */
fs_validate_description(const char * name,const struct fs_parameter_spec * desc)380 bool fs_validate_description(const char *name,
381 	const struct fs_parameter_spec *desc)
382 {
383 	const struct fs_parameter_spec *param, *p2;
384 	bool good = true;
385 
386 	for (param = desc; param->name; param++) {
387 		/* Check for duplicate parameter names */
388 		for (p2 = desc; p2 < param; p2++) {
389 			if (strcmp(param->name, p2->name) == 0) {
390 				if (is_flag(param) != is_flag(p2))
391 					continue;
392 				pr_err("VALIDATE %s: PARAM[%s]: Duplicate\n",
393 				       name, param->name);
394 				good = false;
395 			}
396 		}
397 	}
398 	return good;
399 }
400 #endif /* CONFIG_VALIDATE_FS_PARSER */
401