xref: /kernel/linux/linux-5.10/fs/efivarfs/inode.c (revision 8c2ecf20) 
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
14#include "internal.h"
15
16struct inode *efivarfs_get_inode(struct super_block *sb,
17				const struct inode *dir, int mode,
18				dev_t dev, bool is_removable)
19{
20	struct inode *inode = new_inode(sb);
21
22	if (inode) {
23		inode->i_ino = get_next_ino();
24		inode->i_mode = mode;
25		inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
26		inode->i_flags = is_removable ? 0 : S_IMMUTABLE;
27		switch (mode & S_IFMT) {
28		case S_IFREG:
29			inode->i_fop = &efivarfs_file_operations;
30			break;
31		case S_IFDIR:
32			inode->i_op = &efivarfs_dir_inode_operations;
33			inode->i_fop = &simple_dir_operations;
34			inc_nlink(inode);
35			break;
36		}
37	}
38	return inode;
39}
40
41/*
42 * Return true if 'str' is a valid efivarfs filename of the form,
43 *
44 *	VariableName-12345678-1234-1234-1234-1234567891bc
45 */
46bool efivarfs_valid_name(const char *str, int len)
47{
48	const char *s = str + len - EFI_VARIABLE_GUID_LEN;
49
50	/*
51	 * We need a GUID, plus at least one letter for the variable name,
52	 * plus the '-' separator
53	 */
54	if (len < EFI_VARIABLE_GUID_LEN + 2)
55		return false;
56
57	/* GUID must be preceded by a '-' */
58	if (*(s - 1) != '-')
59		return false;
60
61	/*
62	 * Validate that 's' is of the correct format, e.g.
63	 *
64	 *	12345678-1234-1234-1234-123456789abc
65	 */
66	return uuid_is_valid(s);
67}
68
69static int efivarfs_create(struct inode *dir, struct dentry *dentry,
70			  umode_t mode, bool excl)
71{
72	struct inode *inode = NULL;
73	struct efivar_entry *var;
74	int namelen, i = 0, err = 0;
75	bool is_removable = false;
76
77	if (!efivarfs_valid_name(dentry->d_name.name, dentry->d_name.len))
78		return -EINVAL;
79
80	var = kzalloc(sizeof(struct efivar_entry), GFP_KERNEL);
81	if (!var)
82		return -ENOMEM;
83
84	/* length of the variable name itself: remove GUID and separator */
85	namelen = dentry->d_name.len - EFI_VARIABLE_GUID_LEN - 1;
86
87	err = guid_parse(dentry->d_name.name + namelen + 1, &var->var.VendorGuid);
88	if (err)
89		goto out;
90
91	if (efivar_variable_is_removable(var->var.VendorGuid,
92					 dentry->d_name.name, namelen))
93		is_removable = true;
94
95	inode = efivarfs_get_inode(dir->i_sb, dir, mode, 0, is_removable);
96	if (!inode) {
97		err = -ENOMEM;
98		goto out;
99	}
100
101	for (i = 0; i < namelen; i++)
102		var->var.VariableName[i] = dentry->d_name.name[i];
103
104	var->var.VariableName[i] = '\0';
105
106	inode->i_private = var;
107	kmemleak_ignore(var);
108
109	err = efivar_entry_add(var, &efivarfs_list);
110	if (err)
111		goto out;
112
113	d_instantiate(dentry, inode);
114	dget(dentry);
115out:
116	if (err) {
117		kfree(var);
118		if (inode)
119			iput(inode);
120	}
121	return err;
122}
123
124static int efivarfs_unlink(struct inode *dir, struct dentry *dentry)
125{
126	struct efivar_entry *var = d_inode(dentry)->i_private;
127
128	if (efivar_entry_delete(var))
129		return -EINVAL;
130
131	drop_nlink(d_inode(dentry));
132	dput(dentry);
133	return 0;
134};
135
136const struct inode_operations efivarfs_dir_inode_operations = {
137	.lookup = simple_lookup,
138	.unlink = efivarfs_unlink,
139	.create = efivarfs_create,
140};
141