fs/efivarfs/file.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/delay.h>
   9 #include <linux/fs.h>
  10 #include <linux/slab.h>
  11 #include <linux/mount.h>
  12
  13 #include "internal.h"
  14
  15 static ssize_t efivarfs_file_write(struct file *file,
  16                 const char __user *userbuf, size_t count, loff_t *ppos)
  17 {
  18         struct efivar_entry *var = file->private_data;
  19         void *data;
  20         u32 attributes;
  21         struct inode *inode = file->f_mapping->host;
  22         unsigned long datasize = count - sizeof(attributes);
  23         ssize_t bytes;
  24         bool set = false;
  25
  26         if (count < sizeof(attributes))
  27                 return -EINVAL;
  28
  29         if (copy_from_user(&attributes, userbuf, sizeof(attributes)))
  30                 return -EFAULT;
  31
  32         if (attributes & ~(EFI_VARIABLE_MASK))
  33                 return -EINVAL;
  34
  35         data = memdup_user(userbuf + sizeof(attributes), datasize);
  36         if (IS_ERR(data))
  37                 return PTR_ERR(data);
  38
  39         bytes = efivar_entry_set_get_size(var, attributes, &datasize,
  40                                           data, &set);
  41         if (!set && bytes) {
  42                 if (bytes == -ENOENT)
  43                         bytes = -EIO;
  44                 goto out;
  45         }
  46
  47         if (bytes == -ENOENT) {
  48                 drop_nlink(inode);
  49                 d_delete(file->f_path.dentry);
  50                 dput(file->f_path.dentry);
  51         } else {
  52                 inode_lock(inode);
  53                 i_size_write(inode, datasize + sizeof(attributes));
  54                 inode->i_mtime = current_time(inode);
  55                 inode_unlock(inode);
  56         }
  57
  58         bytes = count;
  59
  60 out:
  61         kfree(data);
  62
  63         return bytes;
  64 }
  65
  66 static ssize_t efivarfs_file_read(struct file *file, char __user *userbuf,
  67                 size_t count, loff_t *ppos)
  68 {
  69         struct efivar_entry *var = file->private_data;
  70         unsigned long datasize = 0;
  71         u32 attributes;
  72         void *data;
  73         ssize_t size = 0;
  74         int err;
  75
  76         while (!__ratelimit(&file->f_cred->user->ratelimit))
  77                 msleep(50);
  78
  79         err = efivar_entry_size(var, &datasize);
  80
  81         /*
  82          * efivarfs represents uncommitted variables with
  83          * zero-length files. Reading them should return EOF.
  84          */
  85         if (err == -ENOENT)
  86                 return 0;
  87         else if (err)
  88                 return err;
  89
  90         data = kmalloc(datasize + sizeof(attributes), GFP_KERNEL);
  91
  92         if (!data)
  93                 return -ENOMEM;
  94
  95         size = efivar_entry_get(var, &attributes, &datasize,
  96                                 data + sizeof(attributes));
  97         if (size)
  98                 goto out_free;
  99
 100         memcpy(data, &attributes, sizeof(attributes));
 101         size = simple_read_from_buffer(userbuf, count, ppos,
 102                                        data, datasize + sizeof(attributes));
 103 out_free:
 104         kfree(data);
 105
 106         return size;
 107 }
 108
 109 const struct file_operations efivarfs_file_operations = {
 110         .open   = simple_open,
 111         .read   = efivarfs_file_read,
 112         .write  = efivarfs_file_write,
 113         .llseek = no_llseek,
 114 };