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 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 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);
 128 out:
 129         if (err) {
 130                 kfree(var);
 131                 if (inode)
 132                         iput(inode);
 133         }
 134         return err;
 135 }
 136
 137 static 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
 149 const struct inode_operations efivarfs_dir_inode_operations = {
 150         .lookup = simple_lookup,
 151         .unlink = efivarfs_unlink,
 152         .create = efivarfs_create,
 153 };
 154
 155 static int
 156 efivarfs_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
 170 static int
 171 efivarfs_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
 190 static const struct inode_operations efivarfs_file_inode_operations = {
 191         .fileattr_get = efivarfs_fileattr_get,
 192         .fileattr_set = efivarfs_fileattr_set,
 193 };