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/slab.h>
  11 #include <linux/uuid.h>
  12
  13 #include "internal.h"
  14
  15 struct inode *efivarfs_get_inode(struct super_block *sb,
  16                                 const struct inode *dir, int mode,
  17                                 dev_t dev, bool is_removable)
  18 {
  19         struct inode *inode = new_inode(sb);
  20
  21         if (inode) {
  22                 inode->i_ino = get_next_ino();
  23                 inode->i_mode = mode;
  24                 inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
  25                 inode->i_flags = is_removable ? 0 : S_IMMUTABLE;
  26                 switch (mode & S_IFMT) {
  27                 case S_IFREG:
  28                         inode->i_fop = &efivarfs_file_operations;
  29                         break;
  30                 case S_IFDIR:
  31                         inode->i_op = &efivarfs_dir_inode_operations;
  32                         inode->i_fop = &simple_dir_operations;
  33                         inc_nlink(inode);
  34                         break;
  35                 }
  36         }
  37         return inode;
  38 }
  39
  40 /*
  41  * Return true if 'str' is a valid efivarfs filename of the form,
  42  *
  43  *      VariableName-12345678-1234-1234-1234-1234567891bc
  44  */
  45 bool efivarfs_valid_name(const char *str, int len)
  46 {
  47         const char *s = str + len - EFI_VARIABLE_GUID_LEN;
  48
  49         /*
  50          * We need a GUID, plus at least one letter for the variable name,
  51          * plus the '-' separator
  52          */
  53         if (len < EFI_VARIABLE_GUID_LEN + 2)
  54                 return false;
  55
  56         /* GUID must be preceded by a '-' */
  57         if (*(s - 1) != '-')
  58                 return false;
  59
  60         /*
  61          * Validate that 's' is of the correct format, e.g.
  62          *
  63          *      12345678-1234-1234-1234-123456789abc
  64          */
  65         return uuid_is_valid(s);
  66 }
  67
  68 static int efivarfs_create(struct inode *dir, struct dentry *dentry,
  69                           umode_t mode, bool excl)
  70 {
  71         struct inode *inode = NULL;
  72         struct efivar_entry *var;
  73         int namelen, i = 0, err = 0;
  74         bool is_removable = false;
  75
  76         if (!efivarfs_valid_name(dentry->d_name.name, dentry->d_name.len))
  77                 return -EINVAL;
  78
  79         var = kzalloc(sizeof(struct efivar_entry), GFP_KERNEL);
  80         if (!var)
  81                 return -ENOMEM;
  82
  83         /* length of the variable name itself: remove GUID and separator */
  84         namelen = dentry->d_name.len - EFI_VARIABLE_GUID_LEN - 1;
  85
  86         err = guid_parse(dentry->d_name.name + namelen + 1, &var->var.VendorGuid);
  87         if (err)
  88                 goto out;
  89
  90         if (efivar_variable_is_removable(var->var.VendorGuid,
  91                                          dentry->d_name.name, namelen))
  92                 is_removable = true;
  93
  94         inode = efivarfs_get_inode(dir->i_sb, dir, mode, 0, is_removable);
  95         if (!inode) {
  96                 err = -ENOMEM;
  97                 goto out;
  98         }
  99
 100         for (i = 0; i < namelen; i++)
 101                 var->var.VariableName[i] = dentry->d_name.name[i];
 102
 103         var->var.VariableName[i] = '\0';
 104
 105         inode->i_private = var;
 106
 107         err = efivar_entry_add(var, &efivarfs_list);
 108         if (err)
 109                 goto out;
 110
 111         d_instantiate(dentry, inode);
 112         dget(dentry);
 113 out:
 114         if (err) {
 115                 kfree(var);
 116                 if (inode)
 117                         iput(inode);
 118         }
 119         return err;
 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 };