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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
26static const struct constant_table *
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 */
41int 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}
47EXPORT_SYMBOL(lookup_constant);
48
49static inline bool is_flag(const struct fs_parameter_spec *p)
50{
51 return p->type == NULL;
52}
53
54static 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 */
103int __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}
134EXPORT_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 * @_path: The result of the lookup
142 */
143int fs_lookup_param(struct fs_context *fc,
144 struct fs_parameter *param,
145 bool want_bdev,
146 struct path *_path)
147{
148 struct filename *f;
149 unsigned int flags = 0;
150 bool put_f;
151 int ret;
152
153 switch (param->type) {
154 case fs_value_is_string:
155 f = getname_kernel(param->string);
156 if (IS_ERR(f))
157 return PTR_ERR(f);
158 put_f = true;
159 break;
160 case fs_value_is_filename:
161 f = param->name;
162 put_f = false;
163 break;
164 default:
165 return invalf(fc, "%s: not usable as path", param->key);
166 }
167
168 f->refcnt++; /* filename_lookup() drops our ref. */
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
185out:
186 if (put_f)
187 putname(f);
188 return ret;
189}
190EXPORT_SYMBOL(fs_lookup_param);
191
192int 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
197int 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 b = lookup_constant(bool_names, param->string, -1);
204 if (b == -1)
205 return fs_param_bad_value(log, param);
206 result->boolean = b;
207 return 0;
208}
209EXPORT_SYMBOL(fs_param_is_bool);
210
211int fs_param_is_u32(struct p_log *log, const struct fs_parameter_spec *p,
212 struct fs_parameter *param, struct fs_parse_result *result)
213{
214 int base = (unsigned long)p->data;
215 if (param->type != fs_value_is_string ||
216 kstrtouint(param->string, base, &result->uint_32) < 0)
217 return fs_param_bad_value(log, param);
218 return 0;
219}
220EXPORT_SYMBOL(fs_param_is_u32);
221
222int fs_param_is_s32(struct p_log *log, const struct fs_parameter_spec *p,
223 struct fs_parameter *param, struct fs_parse_result *result)
224{
225 if (param->type != fs_value_is_string ||
226 kstrtoint(param->string, 0, &result->int_32) < 0)
227 return fs_param_bad_value(log, param);
228 return 0;
229}
230EXPORT_SYMBOL(fs_param_is_s32);
231
232int fs_param_is_u64(struct p_log *log, const struct fs_parameter_spec *p,
233 struct fs_parameter *param, struct fs_parse_result *result)
234{
235 if (param->type != fs_value_is_string ||
236 kstrtoull(param->string, 0, &result->uint_64) < 0)
237 return fs_param_bad_value(log, param);
238 return 0;
239}
240EXPORT_SYMBOL(fs_param_is_u64);
241
242int fs_param_is_enum(struct p_log *log, const struct fs_parameter_spec *p,
243 struct fs_parameter *param, struct fs_parse_result *result)
244{
245 const struct constant_table *c;
246 if (param->type != fs_value_is_string)
247 return fs_param_bad_value(log, param);
248 c = __lookup_constant(p->data, param->string);
249 if (!c)
250 return fs_param_bad_value(log, param);
251 result->uint_32 = c->value;
252 return 0;
253}
254EXPORT_SYMBOL(fs_param_is_enum);
255
256int fs_param_is_string(struct p_log *log, const struct fs_parameter_spec *p,
257 struct fs_parameter *param, struct fs_parse_result *result)
258{
259 if (param->type != fs_value_is_string || !*param->string)
260 return fs_param_bad_value(log, param);
261 return 0;
262}
263EXPORT_SYMBOL(fs_param_is_string);
264
265int fs_param_is_blob(struct p_log *log, const struct fs_parameter_spec *p,
266 struct fs_parameter *param, struct fs_parse_result *result)
267{
268 if (param->type != fs_value_is_blob)
269 return fs_param_bad_value(log, param);
270 return 0;
271}
272EXPORT_SYMBOL(fs_param_is_blob);
273
274int fs_param_is_fd(struct p_log *log, const struct fs_parameter_spec *p,
275 struct fs_parameter *param, struct fs_parse_result *result)
276{
277 switch (param->type) {
278 case fs_value_is_string:
279 if (kstrtouint(param->string, 0, &result->uint_32) < 0)
280 break;
281 if (result->uint_32 <= INT_MAX)
282 return 0;
283 break;
284 case fs_value_is_file:
285 result->uint_32 = param->dirfd;
286 if (result->uint_32 <= INT_MAX)
287 return 0;
288 break;
289 default:
290 break;
291 }
292 return fs_param_bad_value(log, param);
293}
294EXPORT_SYMBOL(fs_param_is_fd);
295
296int fs_param_is_blockdev(struct p_log *log, const struct fs_parameter_spec *p,
297 struct fs_parameter *param, struct fs_parse_result *result)
298{
299 return 0;
300}
301EXPORT_SYMBOL(fs_param_is_blockdev);
302
303int fs_param_is_path(struct p_log *log, const struct fs_parameter_spec *p,
304 struct fs_parameter *param, struct fs_parse_result *result)
305{
306 return 0;
307}
308EXPORT_SYMBOL(fs_param_is_path);
309
310#ifdef CONFIG_VALIDATE_FS_PARSER
311/**
312 * validate_constant_table - Validate a constant table
313 * @name: Name to use in reporting
314 * @tbl: The constant table to validate.
315 * @tbl_size: The size of the table.
316 * @low: The lowest permissible value.
317 * @high: The highest permissible value.
318 * @special: One special permissible value outside of the range.
319 */
320bool validate_constant_table(const struct constant_table *tbl, size_t tbl_size,
321 int low, int high, int special)
322{
323 size_t i;
324 bool good = true;
325
326 if (tbl_size == 0) {
327 pr_warn("VALIDATE C-TBL: Empty\n");
328 return true;
329 }
330
331 for (i = 0; i < tbl_size; i++) {
332 if (!tbl[i].name) {
333 pr_err("VALIDATE C-TBL[%zu]: Null\n", i);
334 good = false;
335 } else if (i > 0 && tbl[i - 1].name) {
336 int c = strcmp(tbl[i-1].name, tbl[i].name);
337
338 if (c == 0) {
339 pr_err("VALIDATE C-TBL[%zu]: Duplicate %s\n",
340 i, tbl[i].name);
341 good = false;
342 }
343 if (c > 0) {
344 pr_err("VALIDATE C-TBL[%zu]: Missorted %s>=%s\n",
345 i, tbl[i-1].name, tbl[i].name);
346 good = false;
347 }
348 }
349
350 if (tbl[i].value != special &&
351 (tbl[i].value < low || tbl[i].value > high)) {
352 pr_err("VALIDATE C-TBL[%zu]: %s->%d const out of range (%d-%d)\n",
353 i, tbl[i].name, tbl[i].value, low, high);
354 good = false;
355 }
356 }
357
358 return good;
359}
360
361/**
362 * fs_validate_description - Validate a parameter description
363 * @desc: The parameter description to validate.
364 */
365bool fs_validate_description(const char *name,
366 const struct fs_parameter_spec *desc)
367{
368 const struct fs_parameter_spec *param, *p2;
369 bool good = true;
370
371 for (param = desc; param->name; param++) {
372 /* Check for duplicate parameter names */
373 for (p2 = desc; p2 < param; p2++) {
374 if (strcmp(param->name, p2->name) == 0) {
375 if (is_flag(param) != is_flag(p2))
376 continue;
377 pr_err("VALIDATE %s: PARAM[%s]: Duplicate\n",
378 name, param->name);
379 good = false;
380 }
381 }
382 }
383 return good;
384}
385#endif /* CONFIG_VALIDATE_FS_PARSER */