LXR linux/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
  17static const struct inode_operations efivarfs_file_inode_operations;
  18
  19struct 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 */
  50bool 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
  73static 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);
 119out:
 120        if (err) {
 121                kfree(var);
 122                if (inode)
 123                        iput(inode);
 124        }
 125        return err;
 126}
 127
 128static 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
 140const struct inode_operations efivarfs_dir_inode_operations = {
 141        .lookup = simple_lookup,
 142        .unlink = efivarfs_unlink,
 143        .create = efivarfs_create,
 144};
 145
 146static int
 147efivarfs_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
 161static int
 162efivarfs_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
 181static const struct inode_operations efivarfs_file_inode_operations = {
 182        .fileattr_get = efivarfs_fileattr_get,
 183        .fileattr_set = efivarfs_fileattr_set,
 184};
 185