fs/efivarfs/super.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/ctype.h>
   8 #include <linux/efi.h>
   9 #include <linux/fs.h>
  10 #include <linux/fs_context.h>
  11 #include <linux/module.h>
  12 #include <linux/pagemap.h>
  13 #include <linux/ucs2_string.h>
  14 #include <linux/slab.h>
  15 #include <linux/magic.h>
  16
  17 #include "internal.h"
  18
  19 LIST_HEAD(efivarfs_list);
  20
  21 static void efivarfs_evict_inode(struct inode *inode)
  22 {
  23         clear_inode(inode);
  24 }
  25
  26 static const struct super_operations efivarfs_ops = {
  27         .statfs = simple_statfs,
  28         .drop_inode = generic_delete_inode,
  29         .evict_inode = efivarfs_evict_inode,
  30 };
  31
  32 /*
  33  * Compare two efivarfs file names.
  34  *
  35  * An efivarfs filename is composed of two parts,
  36  *
  37  *      1. A case-sensitive variable name
  38  *      2. A case-insensitive GUID
  39  *
  40  * So we need to perform a case-sensitive match on part 1 and a
  41  * case-insensitive match on part 2.
  42  */
  43 static int efivarfs_d_compare(const struct dentry *dentry,
  44                               unsigned int len, const char *str,
  45                               const struct qstr *name)
  46 {
  47         int guid = len - EFI_VARIABLE_GUID_LEN;
  48
  49         if (name->len != len)
  50                 return 1;
  51
  52         /* Case-sensitive compare for the variable name */
  53         if (memcmp(str, name->name, guid))
  54                 return 1;
  55
  56         /* Case-insensitive compare for the GUID */
  57         return strncasecmp(name->name + guid, str + guid, EFI_VARIABLE_GUID_LEN);
  58 }
  59
  60 static int efivarfs_d_hash(const struct dentry *dentry, struct qstr *qstr)
  61 {
  62         unsigned long hash = init_name_hash(dentry);
  63         const unsigned char *s = qstr->name;
  64         unsigned int len = qstr->len;
  65
  66         if (!efivarfs_valid_name(s, len))
  67                 return -EINVAL;
  68
  69         while (len-- > EFI_VARIABLE_GUID_LEN)
  70                 hash = partial_name_hash(*s++, hash);
  71
  72         /* GUID is case-insensitive. */
  73         while (len--)
  74                 hash = partial_name_hash(tolower(*s++), hash);
  75
  76         qstr->hash = end_name_hash(hash);
  77         return 0;
  78 }
  79
  80 static const struct dentry_operations efivarfs_d_ops = {
  81         .d_compare = efivarfs_d_compare,
  82         .d_hash = efivarfs_d_hash,
  83         .d_delete = always_delete_dentry,
  84 };
  85
  86 static struct dentry *efivarfs_alloc_dentry(struct dentry *parent, char *name)
  87 {
  88         struct dentry *d;
  89         struct qstr q;
  90         int err;
  91
  92         q.name = name;
  93         q.len = strlen(name);
  94
  95         err = efivarfs_d_hash(parent, &q);
  96         if (err)
  97                 return ERR_PTR(err);
  98
  99         d = d_alloc(parent, &q);
 100         if (d)
 101                 return d;
 102
 103         return ERR_PTR(-ENOMEM);
 104 }
 105
 106 static int efivarfs_callback(efi_char16_t *name16, efi_guid_t vendor,
 107                              unsigned long name_size, void *data)
 108 {
 109         struct super_block *sb = (struct super_block *)data;
 110         struct efivar_entry *entry;
 111         struct inode *inode = NULL;
 112         struct dentry *dentry, *root = sb->s_root;
 113         unsigned long size = 0;
 114         char *name;
 115         int len;
 116         int err = -ENOMEM;
 117         bool is_removable = false;
 118
 119         entry = kzalloc(sizeof(*entry), GFP_KERNEL);
 120         if (!entry)
 121                 return err;
 122
 123         memcpy(entry->var.VariableName, name16, name_size);
 124         memcpy(&(entry->var.VendorGuid), &vendor, sizeof(efi_guid_t));
 125
 126         len = ucs2_utf8size(entry->var.VariableName);
 127
 128         /* name, plus '-', plus GUID, plus NUL*/
 129         name = kmalloc(len + 1 + EFI_VARIABLE_GUID_LEN + 1, GFP_KERNEL);
 130         if (!name)
 131                 goto fail;
 132
 133         ucs2_as_utf8(name, entry->var.VariableName, len);
 134
 135         if (efivar_variable_is_removable(entry->var.VendorGuid, name, len))
 136                 is_removable = true;
 137
 138         name[len] = '-';
 139
 140         efi_guid_to_str(&entry->var.VendorGuid, name + len + 1);
 141
 142         name[len + EFI_VARIABLE_GUID_LEN+1] = '\0';
 143
 144         /* replace invalid slashes like kobject_set_name_vargs does for /sys/firmware/efi/vars. */
 145         strreplace(name, '/', '!');
 146
 147         inode = efivarfs_get_inode(sb, d_inode(root), S_IFREG | 0644, 0,
 148                                    is_removable);
 149         if (!inode)
 150                 goto fail_name;
 151
 152         dentry = efivarfs_alloc_dentry(root, name);
 153         if (IS_ERR(dentry)) {
 154                 err = PTR_ERR(dentry);
 155                 goto fail_inode;
 156         }
 157
 158         __efivar_entry_get(entry, NULL, &size, NULL);
 159         __efivar_entry_add(entry, &efivarfs_list);
 160
 161         /* copied by the above to local storage in the dentry. */
 162         kfree(name);
 163
 164         inode_lock(inode);
 165         inode->i_private = entry;
 166         i_size_write(inode, size + sizeof(entry->var.Attributes));
 167         inode_unlock(inode);
 168         d_add(dentry, inode);
 169
 170         return 0;
 171
 172 fail_inode:
 173         iput(inode);
 174 fail_name:
 175         kfree(name);
 176 fail:
 177         kfree(entry);
 178         return err;
 179 }
 180
 181 static int efivarfs_destroy(struct efivar_entry *entry, void *data)
 182 {
 183         efivar_entry_remove(entry);
 184         kfree(entry);
 185         return 0;
 186 }
 187
 188 static int efivarfs_fill_super(struct super_block *sb, struct fs_context *fc)
 189 {
 190         struct inode *inode = NULL;
 191         struct dentry *root;
 192         int err;
 193
 194         sb->s_maxbytes          = MAX_LFS_FILESIZE;
 195         sb->s_blocksize         = PAGE_SIZE;
 196         sb->s_blocksize_bits    = PAGE_SHIFT;
 197         sb->s_magic             = EFIVARFS_MAGIC;
 198         sb->s_op                = &efivarfs_ops;
 199         sb->s_d_op              = &efivarfs_d_ops;
 200         sb->s_time_gran         = 1;
 201
 202         if (!efivar_supports_writes())
 203                 sb->s_flags |= SB_RDONLY;
 204
 205         inode = efivarfs_get_inode(sb, NULL, S_IFDIR | 0755, 0, true);
 206         if (!inode)
 207                 return -ENOMEM;
 208         inode->i_op = &efivarfs_dir_inode_operations;
 209
 210         root = d_make_root(inode);
 211         sb->s_root = root;
 212         if (!root)
 213                 return -ENOMEM;
 214
 215         INIT_LIST_HEAD(&efivarfs_list);
 216
 217         err = efivar_init(efivarfs_callback, (void *)sb, true, &efivarfs_list);
 218         if (err)
 219                 efivar_entry_iter(efivarfs_destroy, &efivarfs_list, NULL);
 220
 221         return err;
 222 }
 223
 224 static int efivarfs_get_tree(struct fs_context *fc)
 225 {
 226         return get_tree_single(fc, efivarfs_fill_super);
 227 }
 228
 229 static const struct fs_context_operations efivarfs_context_ops = {
 230         .get_tree       = efivarfs_get_tree,
 231 };
 232
 233 static int efivarfs_init_fs_context(struct fs_context *fc)
 234 {
 235         fc->ops = &efivarfs_context_ops;
 236         return 0;
 237 }
 238
 239 static void efivarfs_kill_sb(struct super_block *sb)
 240 {
 241         kill_litter_super(sb);
 242
 243         /* Remove all entries and destroy */
 244         efivar_entry_iter(efivarfs_destroy, &efivarfs_list, NULL);
 245 }
 246
 247 static struct file_system_type efivarfs_type = {
 248         .owner   = THIS_MODULE,
 249         .name    = "efivarfs",
 250         .init_fs_context = efivarfs_init_fs_context,
 251         .kill_sb = efivarfs_kill_sb,
 252 };
 253
 254 static __init int efivarfs_init(void)
 255 {
 256         if (!efivars_kobject())
 257                 return -ENODEV;
 258
 259         return register_filesystem(&efivarfs_type);
 260 }
 261
 262 static __exit void efivarfs_exit(void)
 263 {
 264         unregister_filesystem(&efivarfs_type);
 265 }
 266
 267 MODULE_AUTHOR("Matthew Garrett, Jeremy Kerr");
 268 MODULE_DESCRIPTION("EFI Variable Filesystem");
 269 MODULE_LICENSE("GPL");
 270 MODULE_ALIAS_FS("efivarfs");
 271
 272 module_init(efivarfs_init);
 273 module_exit(efivarfs_exit);