fs_parser.c revision 794ebcea
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	ret = filename_lookup(param->dirfd, f, flags, _path, NULL);
169	if (ret < 0) {
170		errorf(fc, "%s: Lookup failure for '%s'", param->key, f->name);
171		goto out;
172	}
173
174	if (want_bdev &&
175	    !S_ISBLK(d_backing_inode(_path->dentry)->i_mode)) {
176		path_put(_path);
177		_path->dentry = NULL;
178		_path->mnt = NULL;
179		errorf(fc, "%s: Non-blockdev passed as '%s'",
180		       param->key, f->name);
181		ret = -ENOTBLK;
182	}
183
184out:
185	if (put_f)
186		putname(f);
187	return ret;
188}
189EXPORT_SYMBOL(fs_lookup_param);
190
191static int fs_param_bad_value(struct p_log *log, struct fs_parameter *param)
192{
193	return inval_plog(log, "Bad value for '%s'", param->key);
194}
195
196int fs_param_is_bool(struct p_log *log, const struct fs_parameter_spec *p,
197		     struct fs_parameter *param, struct fs_parse_result *result)
198{
199	int b;
200	if (param->type != fs_value_is_string)
201		return fs_param_bad_value(log, param);
202	b = lookup_constant(bool_names, param->string, -1);
203	if (b == -1)
204		return fs_param_bad_value(log, param);
205	result->boolean = b;
206	return 0;
207}
208EXPORT_SYMBOL(fs_param_is_bool);
209
210int fs_param_is_u32(struct p_log *log, const struct fs_parameter_spec *p,
211		    struct fs_parameter *param, struct fs_parse_result *result)
212{
213	int base = (unsigned long)p->data;
214	if (param->type != fs_value_is_string ||
215	    kstrtouint(param->string, base, &result->uint_32) < 0)
216		return fs_param_bad_value(log, param);
217	return 0;
218}
219EXPORT_SYMBOL(fs_param_is_u32);
220
221int fs_param_is_s32(struct p_log *log, const struct fs_parameter_spec *p,
222		    struct fs_parameter *param, struct fs_parse_result *result)
223{
224	if (param->type != fs_value_is_string ||
225	    kstrtoint(param->string, 0, &result->int_32) < 0)
226		return fs_param_bad_value(log, param);
227	return 0;
228}
229EXPORT_SYMBOL(fs_param_is_s32);
230
231int fs_param_is_u64(struct p_log *log, const struct fs_parameter_spec *p,
232		    struct fs_parameter *param, struct fs_parse_result *result)
233{
234	if (param->type != fs_value_is_string ||
235	    kstrtoull(param->string, 0, &result->uint_64) < 0)
236		return fs_param_bad_value(log, param);
237	return 0;
238}
239EXPORT_SYMBOL(fs_param_is_u64);
240
241int fs_param_is_enum(struct p_log *log, const struct fs_parameter_spec *p,
242		     struct fs_parameter *param, struct fs_parse_result *result)
243{
244	const struct constant_table *c;
245	if (param->type != fs_value_is_string)
246		return fs_param_bad_value(log, param);
247	c = __lookup_constant(p->data, param->string);
248	if (!c)
249		return fs_param_bad_value(log, param);
250	result->uint_32 = c->value;
251	return 0;
252}
253EXPORT_SYMBOL(fs_param_is_enum);
254
255int fs_param_is_string(struct p_log *log, const struct fs_parameter_spec *p,
256		       struct fs_parameter *param, struct fs_parse_result *result)
257{
258	if (param->type != fs_value_is_string || !*param->string)
259		return fs_param_bad_value(log, param);
260	return 0;
261}
262EXPORT_SYMBOL(fs_param_is_string);
263
264int fs_param_is_blob(struct p_log *log, const struct fs_parameter_spec *p,
265		     struct fs_parameter *param, struct fs_parse_result *result)
266{
267	if (param->type != fs_value_is_blob)
268		return fs_param_bad_value(log, param);
269	return 0;
270}
271EXPORT_SYMBOL(fs_param_is_blob);
272
273int fs_param_is_fd(struct p_log *log, const struct fs_parameter_spec *p,
274		  struct fs_parameter *param, struct fs_parse_result *result)
275{
276	switch (param->type) {
277	case fs_value_is_string:
278		if (kstrtouint(param->string, 0, &result->uint_32) < 0)
279			break;
280		if (result->uint_32 <= INT_MAX)
281			return 0;
282		break;
283	case fs_value_is_file:
284		result->uint_32 = param->dirfd;
285		if (result->uint_32 <= INT_MAX)
286			return 0;
287		break;
288	default:
289		break;
290	}
291	return fs_param_bad_value(log, param);
292}
293EXPORT_SYMBOL(fs_param_is_fd);
294
295int fs_param_is_blockdev(struct p_log *log, const struct fs_parameter_spec *p,
296		  struct fs_parameter *param, struct fs_parse_result *result)
297{
298	return 0;
299}
300EXPORT_SYMBOL(fs_param_is_blockdev);
301
302int fs_param_is_path(struct p_log *log, const struct fs_parameter_spec *p,
303		     struct fs_parameter *param, struct fs_parse_result *result)
304{
305	return 0;
306}
307EXPORT_SYMBOL(fs_param_is_path);
308
309#ifdef CONFIG_VALIDATE_FS_PARSER
310/**
311 * validate_constant_table - Validate a constant table
312 * @tbl: The constant table to validate.
313 * @tbl_size: The size of the table.
314 * @low: The lowest permissible value.
315 * @high: The highest permissible value.
316 * @special: One special permissible value outside of the range.
317 */
318bool validate_constant_table(const struct constant_table *tbl, size_t tbl_size,
319			     int low, int high, int special)
320{
321	size_t i;
322	bool good = true;
323
324	if (tbl_size == 0) {
325		pr_warn("VALIDATE C-TBL: Empty\n");
326		return true;
327	}
328
329	for (i = 0; i < tbl_size; i++) {
330		if (!tbl[i].name) {
331			pr_err("VALIDATE C-TBL[%zu]: Null\n", i);
332			good = false;
333		} else if (i > 0 && tbl[i - 1].name) {
334			int c = strcmp(tbl[i-1].name, tbl[i].name);
335
336			if (c == 0) {
337				pr_err("VALIDATE C-TBL[%zu]: Duplicate %s\n",
338				       i, tbl[i].name);
339				good = false;
340			}
341			if (c > 0) {
342				pr_err("VALIDATE C-TBL[%zu]: Missorted %s>=%s\n",
343				       i, tbl[i-1].name, tbl[i].name);
344				good = false;
345			}
346		}
347
348		if (tbl[i].value != special &&
349		    (tbl[i].value < low || tbl[i].value > high)) {
350			pr_err("VALIDATE C-TBL[%zu]: %s->%d const out of range (%d-%d)\n",
351			       i, tbl[i].name, tbl[i].value, low, high);
352			good = false;
353		}
354	}
355
356	return good;
357}
358
359/**
360 * fs_validate_description - Validate a parameter description
361 * @name: The parameter name to search for.
362 * @desc: The parameter description to validate.
363 */
364bool fs_validate_description(const char *name,
365	const struct fs_parameter_spec *desc)
366{
367	const struct fs_parameter_spec *param, *p2;
368	bool good = true;
369
370	for (param = desc; param->name; param++) {
371		/* Check for duplicate parameter names */
372		for (p2 = desc; p2 < param; p2++) {
373			if (strcmp(param->name, p2->name) == 0) {
374				if (is_flag(param) != is_flag(p2))
375					continue;
376				pr_err("VALIDATE %s: PARAM[%s]: Duplicate\n",
377				       name, param->name);
378				good = false;
379			}
380		}
381	}
382	return good;
383}
384#endif /* CONFIG_VALIDATE_FS_PARSER */
385