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 * @log: 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 * @flags: Pathwalk flags passed to filename_lookup()
142 * @_path: The result of the lookup
143 */
144int 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
185out:
186	if (put_f)
187		putname(f);
188	return ret;
189}
190EXPORT_SYMBOL(fs_lookup_param);
191
192static 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
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	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}
211EXPORT_SYMBOL(fs_param_is_bool);
212
213int 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}
225EXPORT_SYMBOL(fs_param_is_u32);
226
227int 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}
238EXPORT_SYMBOL(fs_param_is_s32);
239
240int 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}
251EXPORT_SYMBOL(fs_param_is_u64);
252
253int 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}
267EXPORT_SYMBOL(fs_param_is_enum);
268
269int 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}
277EXPORT_SYMBOL(fs_param_is_string);
278
279int 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}
286EXPORT_SYMBOL(fs_param_is_blob);
287
288int 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}
309EXPORT_SYMBOL(fs_param_is_fd);
310
311int 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}
316EXPORT_SYMBOL(fs_param_is_blockdev);
317
318int 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}
323EXPORT_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 */
334bool 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 */
380bool 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