1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * Copyright (C) 2012 Red Hat, Inc.
4 * Copyright (C) 2012 Jeremy Kerr <jeremy.kerr@canonical.com>
5 */
6
7#include <linux/efi.h>
8#include <linux/fs.h>
9#include <linux/ctype.h>
10#include <linux/kmemleak.h>
11#include <linux/slab.h>
12#include <linux/uuid.h>
13#include <linux/fileattr.h>
14
15#include "internal.h"
16
17static const struct inode_operations efivarfs_file_inode_operations;
18
19struct inode *efivarfs_get_inode(struct super_block *sb,
20				const struct inode *dir, int mode,
21				dev_t dev, bool is_removable)
22{
23	struct inode *inode = new_inode(sb);
24	struct efivarfs_fs_info *fsi = sb->s_fs_info;
25	struct efivarfs_mount_opts *opts = &fsi->mount_opts;
26
27	if (inode) {
28		inode->i_uid = opts->uid;
29		inode->i_gid = opts->gid;
30		inode->i_ino = get_next_ino();
31		inode->i_mode = mode;
32		simple_inode_init_ts(inode);
33		inode->i_flags = is_removable ? 0 : S_IMMUTABLE;
34		switch (mode & S_IFMT) {
35		case S_IFREG:
36			inode->i_op = &efivarfs_file_inode_operations;
37			inode->i_fop = &efivarfs_file_operations;
38			break;
39		case S_IFDIR:
40			inode->i_op = &efivarfs_dir_inode_operations;
41			inode->i_fop = &simple_dir_operations;
42			inc_nlink(inode);
43			break;
44		}
45	}
46	return inode;
47}
48
49/*
50 * Return true if 'str' is a valid efivarfs filename of the form,
51 *
52 *	VariableName-12345678-1234-1234-1234-1234567891bc
53 */
54bool efivarfs_valid_name(const char *str, int len)
55{
56	const char *s = str + len - EFI_VARIABLE_GUID_LEN;
57
58	/*
59	 * We need a GUID, plus at least one letter for the variable name,
60	 * plus the '-' separator
61	 */
62	if (len < EFI_VARIABLE_GUID_LEN + 2)
63		return false;
64
65	/* GUID must be preceded by a '-' */
66	if (*(s - 1) != '-')
67		return false;
68
69	/*
70	 * Validate that 's' is of the correct format, e.g.
71	 *
72	 *	12345678-1234-1234-1234-123456789abc
73	 */
74	return uuid_is_valid(s);
75}
76
77static int efivarfs_create(struct mnt_idmap *idmap, struct inode *dir,
78			   struct dentry *dentry, umode_t mode, bool excl)
79{
80	struct efivarfs_fs_info *info = dir->i_sb->s_fs_info;
81	struct inode *inode = NULL;
82	struct efivar_entry *var;
83	int namelen, i = 0, err = 0;
84	bool is_removable = false;
85
86	if (!efivarfs_valid_name(dentry->d_name.name, dentry->d_name.len))
87		return -EINVAL;
88
89	var = kzalloc(sizeof(struct efivar_entry), GFP_KERNEL);
90	if (!var)
91		return -ENOMEM;
92
93	/* length of the variable name itself: remove GUID and separator */
94	namelen = dentry->d_name.len - EFI_VARIABLE_GUID_LEN - 1;
95
96	err = guid_parse(dentry->d_name.name + namelen + 1, &var->var.VendorGuid);
97	if (err)
98		goto out;
99	if (guid_equal(&var->var.VendorGuid, &LINUX_EFI_RANDOM_SEED_TABLE_GUID)) {
100		err = -EPERM;
101		goto out;
102	}
103
104	if (efivar_variable_is_removable(var->var.VendorGuid,
105					 dentry->d_name.name, namelen))
106		is_removable = true;
107
108	inode = efivarfs_get_inode(dir->i_sb, dir, mode, 0, is_removable);
109	if (!inode) {
110		err = -ENOMEM;
111		goto out;
112	}
113
114	for (i = 0; i < namelen; i++)
115		var->var.VariableName[i] = dentry->d_name.name[i];
116
117	var->var.VariableName[i] = '\0';
118
119	inode->i_private = var;
120	kmemleak_ignore(var);
121
122	err = efivar_entry_add(var, &info->efivarfs_list);
123	if (err)
124		goto out;
125
126	d_instantiate(dentry, inode);
127	dget(dentry);
128out:
129	if (err) {
130		kfree(var);
131		if (inode)
132			iput(inode);
133	}
134	return err;
135}
136
137static int efivarfs_unlink(struct inode *dir, struct dentry *dentry)
138{
139	struct efivar_entry *var = d_inode(dentry)->i_private;
140
141	if (efivar_entry_delete(var))
142		return -EINVAL;
143
144	drop_nlink(d_inode(dentry));
145	dput(dentry);
146	return 0;
147};
148
149const struct inode_operations efivarfs_dir_inode_operations = {
150	.lookup = simple_lookup,
151	.unlink = efivarfs_unlink,
152	.create = efivarfs_create,
153};
154
155static int
156efivarfs_fileattr_get(struct dentry *dentry, struct fileattr *fa)
157{
158	unsigned int i_flags;
159	unsigned int flags = 0;
160
161	i_flags = d_inode(dentry)->i_flags;
162	if (i_flags & S_IMMUTABLE)
163		flags |= FS_IMMUTABLE_FL;
164
165	fileattr_fill_flags(fa, flags);
166
167	return 0;
168}
169
170static int
171efivarfs_fileattr_set(struct mnt_idmap *idmap,
172		      struct dentry *dentry, struct fileattr *fa)
173{
174	unsigned int i_flags = 0;
175
176	if (fileattr_has_fsx(fa))
177		return -EOPNOTSUPP;
178
179	if (fa->flags & ~FS_IMMUTABLE_FL)
180		return -EOPNOTSUPP;
181
182	if (fa->flags & FS_IMMUTABLE_FL)
183		i_flags |= S_IMMUTABLE;
184
185	inode_set_flags(d_inode(dentry), i_flags, S_IMMUTABLE);
186
187	return 0;
188}
189
190static const struct inode_operations efivarfs_file_inode_operations = {
191	.fileattr_get = efivarfs_fileattr_get,
192	.fileattr_set = efivarfs_fileattr_set,
193};
194