inode.c

  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 */
 54static bool 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 inode *inode = NULL;
 81	struct efivar_entry *var;
 82	int namelen, i = 0, err = 0;
 83	bool is_removable = false;
 84	efi_guid_t vendor;
 85
 86	if (!efivarfs_valid_name(dentry->d_name.name, dentry->d_name.len))
 87		return -EINVAL;
 88
 89	/* length of the variable name itself: remove GUID and separator */
 90	namelen = dentry->d_name.len - EFI_VARIABLE_GUID_LEN - 1;
 91
 92	err = guid_parse(dentry->d_name.name + namelen + 1, &vendor);
 93	if (err)
 94		return err;
 95	if (guid_equal(&vendor, &LINUX_EFI_RANDOM_SEED_TABLE_GUID))
 96		return -EPERM;
 97
 98	if (efivar_variable_is_removable(vendor,
 99					 dentry->d_name.name, namelen))
100		is_removable = true;
101
102	inode = efivarfs_get_inode(dir->i_sb, dir, mode, 0, is_removable);
103	if (!inode)
104		return -ENOMEM;
105	var = efivar_entry(inode);
106
107	var->var.VendorGuid = vendor;
108
109	for (i = 0; i < namelen; i++)
110		var->var.VariableName[i] = dentry->d_name.name[i];
111
112	var->var.VariableName[i] = '\0';
113
114	inode->i_private = var;
115
116	d_make_persistent(dentry, inode);
117
118	return 0;
119}
120
121static int efivarfs_unlink(struct inode *dir, struct dentry *dentry)
122{
123	struct efivar_entry *var = d_inode(dentry)->i_private;
124
125	if (efivar_entry_delete(var))
126		return -EINVAL;
127
128	return simple_unlink(dir, dentry);
129};
130
131const struct inode_operations efivarfs_dir_inode_operations = {
132	.lookup = simple_lookup,
133	.unlink = efivarfs_unlink,
134	.create = efivarfs_create,
135};
136
137static int
138efivarfs_fileattr_get(struct dentry *dentry, struct file_kattr *fa)
139{
140	unsigned int i_flags;
141	unsigned int flags = 0;
142
143	i_flags = d_inode(dentry)->i_flags;
144	if (i_flags & S_IMMUTABLE)
145		flags |= FS_IMMUTABLE_FL;
146
147	fileattr_fill_flags(fa, flags);
148
149	return 0;
150}
151
152static int
153efivarfs_fileattr_set(struct mnt_idmap *idmap,
154		      struct dentry *dentry, struct file_kattr *fa)
155{
156	unsigned int i_flags = 0;
157
158	if (fileattr_has_fsx(fa))
159		return -EOPNOTSUPP;
160
161	if (fa->flags & ~FS_IMMUTABLE_FL)
162		return -EOPNOTSUPP;
163
164	if (fa->flags & FS_IMMUTABLE_FL)
165		i_flags |= S_IMMUTABLE;
166
167	inode_set_flags(d_inode(dentry), i_flags, S_IMMUTABLE);
168
169	return 0;
170}
171
172/* copy of simple_setattr except that it doesn't do i_size updates */
173static int efivarfs_setattr(struct mnt_idmap *idmap, struct dentry *dentry,
174		   struct iattr *iattr)
175{
176	struct inode *inode = d_inode(dentry);
177	int error;
178
179	error = setattr_prepare(idmap, dentry, iattr);
180	if (error)
181		return error;
182
183	setattr_copy(idmap, inode, iattr);
184	mark_inode_dirty(inode);
185	return 0;
186}
187
188static const struct inode_operations efivarfs_file_inode_operations = {
189	.fileattr_get = efivarfs_fileattr_get,
190	.fileattr_set = efivarfs_fileattr_set,
191	.setattr      = efivarfs_setattr,
192};