fs/efivarfs/file.c

0001 // SPDX-License-Identifier: GPL-2.0-only
0002 /*
0003  * Copyright (C) 2012 Red Hat, Inc.
0004  * Copyright (C) 2012 Jeremy Kerr <jeremy.kerr@canonical.com>
0005  */
0006
0007 #include <linux/efi.h>
0008 #include <linux/delay.h>
0009 #include <linux/fs.h>
0010 #include <linux/slab.h>
0011 #include <linux/mount.h>
0012
0013 #include "internal.h"
0014
0015 static ssize_t efivarfs_file_write(struct file *file,
0016         const char __user *userbuf, size_t count, loff_t *ppos)
0017 {
0018     struct efivar_entry *var = file->private_data;
0019     void *data;
0020     u32 attributes;
0021     struct inode *inode = file->f_mapping->host;
0022     unsigned long datasize = count - sizeof(attributes);
0023     ssize_t bytes;
0024     bool set = false;
0025
0026     if (count < sizeof(attributes))
0027         return -EINVAL;
0028
0029     if (copy_from_user(&attributes, userbuf, sizeof(attributes)))
0030         return -EFAULT;
0031
0032     if (attributes & ~(EFI_VARIABLE_MASK))
0033         return -EINVAL;
0034
0035     data = memdup_user(userbuf + sizeof(attributes), datasize);
0036     if (IS_ERR(data))
0037         return PTR_ERR(data);
0038
0039     bytes = efivar_entry_set_get_size(var, attributes, &datasize,
0040                       data, &set);
0041     if (!set && bytes) {
0042         if (bytes == -ENOENT)
0043             bytes = -EIO;
0044         goto out;
0045     }
0046
0047     if (bytes == -ENOENT) {
0048         drop_nlink(inode);
0049         d_delete(file->f_path.dentry);
0050         dput(file->f_path.dentry);
0051     } else {
0052         inode_lock(inode);
0053         i_size_write(inode, datasize + sizeof(attributes));
0054         inode->i_mtime = current_time(inode);
0055         inode_unlock(inode);
0056     }
0057
0058     bytes = count;
0059
0060 out:
0061     kfree(data);
0062
0063     return bytes;
0064 }
0065
0066 static ssize_t efivarfs_file_read(struct file *file, char __user *userbuf,
0067         size_t count, loff_t *ppos)
0068 {
0069     struct efivar_entry *var = file->private_data;
0070     unsigned long datasize = 0;
0071     u32 attributes;
0072     void *data;
0073     ssize_t size = 0;
0074     int err;
0075
0076     while (!__ratelimit(&file->f_cred->user->ratelimit))
0077         msleep(50);
0078
0079     err = efivar_entry_size(var, &datasize);
0080
0081     /*
0082      * efivarfs represents uncommitted variables with
0083      * zero-length files. Reading them should return EOF.
0084      */
0085     if (err == -ENOENT)
0086         return 0;
0087     else if (err)
0088         return err;
0089
0090     data = kmalloc(datasize + sizeof(attributes), GFP_KERNEL);
0091
0092     if (!data)
0093         return -ENOMEM;
0094
0095     size = efivar_entry_get(var, &attributes, &datasize,
0096                 data + sizeof(attributes));
0097     if (size)
0098         goto out_free;
0099
0100     memcpy(data, &attributes, sizeof(attributes));
0101     size = simple_read_from_buffer(userbuf, count, ppos,
0102                        data, datasize + sizeof(attributes));
0103 out_free:
0104     kfree(data);
0105
0106     return size;
0107 }
0108
0109 const struct file_operations efivarfs_file_operations = {
0110     .open   = simple_open,
0111     .read   = efivarfs_file_read,
0112     .write  = efivarfs_file_write,
0113     .llseek = no_llseek,
0114 };