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
  14 #include "internal.h"
  15
  16 struct inode *efivarfs_get_inode(struct super_block *sb,
  17                                 const struct inode *dir, int mode,
  18                                 dev_t dev, bool is_removable)
  19 {
  20         struct inode *inode = new_inode(sb);
  21
  22         if (inode) {
  23                 inode->i_ino = get_next_ino();
  24                 inode->i_mode = mode;
  25                 inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
  26                 inode->i_flags = is_removable ? 0 : S_IMMUTABLE;
  27                 switch (mode & S_IFMT) {
  28                 case S_IFREG:
  29                         inode->i_fop = &efivarfs_file_operations;
  30                         break;
  31                 case S_IFDIR:
  32                         inode->i_op = &efivarfs_dir_inode_operations;
  33                         inode->i_fop = &simple_dir_operations;
  34                         inc_nlink(inode);
  35                         break;
  36                 }
  37         }
  38         return inode;
  39 }
  40
  41 /*
  42  * Return true if 'str' is a valid efivarfs filename of the form,
  43  *
  44  *      VariableName-12345678-1234-1234-1234-1234567891bc
  45  */
  46 bool efivarfs_valid_name(const char *str, int len)
  47 {
  48         const char *s = str + len - EFI_VARIABLE_GUID_LEN;
  49
  50         /*
  51          * We need a GUID, plus at least one letter for the variable name,
  52          * plus the '-' separator
  53          */
  54         if (len < EFI_VARIABLE_GUID_LEN + 2)
  55                 return false;
  56
  57         /* GUID must be preceded by a '-' */
  58         if (*(s - 1) != '-')
  59                 return false;
  60
  61         /*
  62          * Validate that 's' is of the correct format, e.g.
  63          *
  64          *      12345678-1234-1234-1234-123456789abc
  65          */
  66         return uuid_is_valid(s);
  67 }
  68
  69 static int efivarfs_create(struct inode *dir, struct dentry *dentry,
  70                           umode_t mode, bool excl)
  71 {
  72         struct inode *inode = NULL;
  73         struct efivar_entry *var;
  74         int namelen, i = 0, err = 0;
  75         bool is_removable = false;
  76
  77         if (!efivarfs_valid_name(dentry->d_name.name, dentry->d_name.len))
  78                 return -EINVAL;
  79
  80         var = kzalloc(sizeof(struct efivar_entry), GFP_KERNEL);
  81         if (!var)
  82                 return -ENOMEM;
  83
  84         /* length of the variable name itself: remove GUID and separator */
  85         namelen = dentry->d_name.len - EFI_VARIABLE_GUID_LEN - 1;
  86
  87         err = guid_parse(dentry->d_name.name + namelen + 1, &var->var.VendorGuid);
  88         if (err)
  89                 goto out;
  90
  91         if (efivar_variable_is_removable(var->var.VendorGuid,
  92                                          dentry->d_name.name, namelen))
  93                 is_removable = true;
  94
  95         inode = efivarfs_get_inode(dir->i_sb, dir, mode, 0, is_removable);
  96         if (!inode) {
  97                 err = -ENOMEM;
  98                 goto out;
  99         }
 100
 101         for (i = 0; i < namelen; i++)
 102                 var->var.VariableName[i] = dentry->d_name.name[i];
 103
 104         var->var.VariableName[i] = '\0';
 105
 106         inode->i_private = var;
 107         kmemleak_ignore(var);
 108
 109         err = efivar_entry_add(var, &efivarfs_list);
 110         if (err)
 111                 goto out;
 112
 113         d_instantiate(dentry, inode);
 114         dget(dentry);
 115 out:
 116         if (err) {
 117                 kfree(var);
 118                 if (inode)
 119                         iput(inode);
 120         }
 121         return err;
 122 }
 123
 124 static int efivarfs_unlink(struct inode *dir, struct dentry *dentry)
 125 {
 126         struct efivar_entry *var = d_inode(dentry)->i_private;
 127
 128         if (efivar_entry_delete(var))
 129                 return -EINVAL;
 130
 131         drop_nlink(d_inode(dentry));
 132         dput(dentry);
 133         return 0;
 134 };
 135
 136 const struct inode_operations efivarfs_dir_inode_operations = {
 137         .lookup = simple_lookup,
 138         .unlink = efivarfs_unlink,
 139         .create = efivarfs_create,
 140 };