fs/efivarfs/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
  17 static const struct inode_operations efivarfs_file_inode_operations;
  18
  19 struct 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  */
  54 static 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
  77 static 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_instantiate(dentry, inode);
 117         dget(dentry);
 118
 119         return 0;
 120 }
 121
 122 static int efivarfs_unlink(struct inode *dir, struct dentry *dentry)
 123 {
 124         struct efivar_entry *var = d_inode(dentry)->i_private;
 125
 126         if (efivar_entry_delete(var))
 127                 return -EINVAL;
 128
 129         drop_nlink(d_inode(dentry));
 130         dput(dentry);
 131         return 0;
 132 };
 133
 134 const struct inode_operations efivarfs_dir_inode_operations = {
 135         .lookup = simple_lookup,
 136         .unlink = efivarfs_unlink,
 137         .create = efivarfs_create,
 138 };
 139
 140 static int
 141 efivarfs_fileattr_get(struct dentry *dentry, struct fileattr *fa)
 142 {
 143         unsigned int i_flags;
 144         unsigned int flags = 0;
 145
 146         i_flags = d_inode(dentry)->i_flags;
 147         if (i_flags & S_IMMUTABLE)
 148                 flags |= FS_IMMUTABLE_FL;
 149
 150         fileattr_fill_flags(fa, flags);
 151
 152         return 0;
 153 }
 154
 155 static int
 156 efivarfs_fileattr_set(struct mnt_idmap *idmap,
 157                       struct dentry *dentry, struct fileattr *fa)
 158 {
 159         unsigned int i_flags = 0;
 160
 161         if (fileattr_has_fsx(fa))
 162                 return -EOPNOTSUPP;
 163
 164         if (fa->flags & ~FS_IMMUTABLE_FL)
 165                 return -EOPNOTSUPP;
 166
 167         if (fa->flags & FS_IMMUTABLE_FL)
 168                 i_flags |= S_IMMUTABLE;
 169
 170         inode_set_flags(d_inode(dentry), i_flags, S_IMMUTABLE);
 171
 172         return 0;
 173 }
 174
 175 /* copy of simple_setattr except that it doesn't do i_size updates */
 176 static int efivarfs_setattr(struct mnt_idmap *idmap, struct dentry *dentry,
 177                    struct iattr *iattr)
 178 {
 179         struct inode *inode = d_inode(dentry);
 180         int error;
 181
 182         error = setattr_prepare(idmap, dentry, iattr);
 183         if (error)
 184                 return error;
 185
 186         setattr_copy(idmap, inode, iattr);
 187         mark_inode_dirty(inode);
 188         return 0;
 189 }
 190
 191 static const struct inode_operations efivarfs_file_inode_operations = {
 192         .fileattr_get = efivarfs_fileattr_get,
 193         .fileattr_set = efivarfs_fileattr_set,
 194         .setattr      = efivarfs_setattr,
 195 };