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
  25         if (inode) {
  26                 inode->i_ino = get_next_ino();
  27                 inode->i_mode = mode;
  28                 inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
  29                 inode->i_flags = is_removable ? 0 : S_IMMUTABLE;
  30                 switch (mode & S_IFMT) {
  31                 case S_IFREG:
  32                         inode->i_op = &efivarfs_file_inode_operations;
  33                         inode->i_fop = &efivarfs_file_operations;
  34                         break;
  35                 case S_IFDIR:
  36                         inode->i_op = &efivarfs_dir_inode_operations;
  37                         inode->i_fop = &simple_dir_operations;
  38                         inc_nlink(inode);
  39                         break;
  40                 }
  41         }
  42         return inode;
  43 }
  44
  45 /*
  46  * Return true if 'str' is a valid efivarfs filename of the form,
  47  *
  48  *      VariableName-12345678-1234-1234-1234-1234567891bc
  49  */
  50 bool efivarfs_valid_name(const char *str, int len)
  51 {
  52         const char *s = str + len - EFI_VARIABLE_GUID_LEN;
  53
  54         /*
  55          * We need a GUID, plus at least one letter for the variable name,
  56          * plus the '-' separator
  57          */
  58         if (len < EFI_VARIABLE_GUID_LEN + 2)
  59                 return false;
  60
  61         /* GUID must be preceded by a '-' */
  62         if (*(s - 1) != '-')
  63                 return false;
  64
  65         /*
  66          * Validate that 's' is of the correct format, e.g.
  67          *
  68          *      12345678-1234-1234-1234-123456789abc
  69          */
  70         return uuid_is_valid(s);
  71 }
  72
  73 static int efivarfs_create(struct user_namespace *mnt_userns, struct inode *dir,
  74                            struct dentry *dentry, umode_t mode, bool excl)
  75 {
  76         struct inode *inode = NULL;
  77         struct efivar_entry *var;
  78         int namelen, i = 0, err = 0;
  79         bool is_removable = false;
  80
  81         if (!efivarfs_valid_name(dentry->d_name.name, dentry->d_name.len))
  82                 return -EINVAL;
  83
  84         var = kzalloc(sizeof(struct efivar_entry), GFP_KERNEL);
  85         if (!var)
  86                 return -ENOMEM;
  87
  88         /* length of the variable name itself: remove GUID and separator */
  89         namelen = dentry->d_name.len - EFI_VARIABLE_GUID_LEN - 1;
  90
  91         err = guid_parse(dentry->d_name.name + namelen + 1, &var->var.VendorGuid);
  92         if (err)
  93                 goto out;
  94
  95         if (efivar_variable_is_removable(var->var.VendorGuid,
  96                                          dentry->d_name.name, namelen))
  97                 is_removable = true;
  98
  99         inode = efivarfs_get_inode(dir->i_sb, dir, mode, 0, is_removable);
 100         if (!inode) {
 101                 err = -ENOMEM;
 102                 goto out;
 103         }
 104
 105         for (i = 0; i < namelen; i++)
 106                 var->var.VariableName[i] = dentry->d_name.name[i];
 107
 108         var->var.VariableName[i] = '\0';
 109
 110         inode->i_private = var;
 111         kmemleak_ignore(var);
 112
 113         err = efivar_entry_add(var, &efivarfs_list);
 114         if (err)
 115                 goto out;
 116
 117         d_instantiate(dentry, inode);
 118         dget(dentry);
 119 out:
 120         if (err) {
 121                 kfree(var);
 122                 if (inode)
 123                         iput(inode);
 124         }
 125         return err;
 126 }
 127
 128 static int efivarfs_unlink(struct inode *dir, struct dentry *dentry)
 129 {
 130         struct efivar_entry *var = d_inode(dentry)->i_private;
 131
 132         if (efivar_entry_delete(var))
 133                 return -EINVAL;
 134
 135         drop_nlink(d_inode(dentry));
 136         dput(dentry);
 137         return 0;
 138 };
 139
 140 const struct inode_operations efivarfs_dir_inode_operations = {
 141         .lookup = simple_lookup,
 142         .unlink = efivarfs_unlink,
 143         .create = efivarfs_create,
 144 };
 145
 146 static int
 147 efivarfs_fileattr_get(struct dentry *dentry, struct fileattr *fa)
 148 {
 149         unsigned int i_flags;
 150         unsigned int flags = 0;
 151
 152         i_flags = d_inode(dentry)->i_flags;
 153         if (i_flags & S_IMMUTABLE)
 154                 flags |= FS_IMMUTABLE_FL;
 155
 156         fileattr_fill_flags(fa, flags);
 157
 158         return 0;
 159 }
 160
 161 static int
 162 efivarfs_fileattr_set(struct user_namespace *mnt_userns,
 163                       struct dentry *dentry, struct fileattr *fa)
 164 {
 165         unsigned int i_flags = 0;
 166
 167         if (fileattr_has_fsx(fa))
 168                 return -EOPNOTSUPP;
 169
 170         if (fa->flags & ~FS_IMMUTABLE_FL)
 171                 return -EOPNOTSUPP;
 172
 173         if (fa->flags & FS_IMMUTABLE_FL)
 174                 i_flags |= S_IMMUTABLE;
 175
 176         inode_set_flags(d_inode(dentry), i_flags, S_IMMUTABLE);
 177
 178         return 0;
 179 }
 180
 181 static const struct inode_operations efivarfs_file_inode_operations = {
 182         .fileattr_get = efivarfs_fileattr_get,
 183         .fileattr_set = efivarfs_fileattr_set,
 184 };