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
 15static 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	inode_lock(inode);
 40	if (var->removed) {
 41		/*
 42		 * file got removed; don't allow a set.  Caused by an
 43		 * unsuccessful create or successful delete write
 44		 * racing with us.
 45		 */
 46		bytes = -EIO;
 47		goto out;
 48	}
 49
 50	bytes = efivar_entry_set_get_size(var, attributes, &datasize,
 51					  data, &set);
 52	if (!set) {
 53		if (bytes == -ENOENT)
 54			bytes = -EIO;
 55		goto out;
 56	}
 57
 58	if (bytes == -ENOENT) {
 59		/*
 60		 * zero size signals to release that the write deleted
 61		 * the variable
 62		 */
 63		i_size_write(inode, 0);
 64	} else {
 65		i_size_write(inode, datasize + sizeof(attributes));
 66		inode_set_mtime_to_ts(inode, inode_set_ctime_current(inode));
 67	}
 68
 69	bytes = count;
 70
 71out:
 72	inode_unlock(inode);
 73
 74	kfree(data);
 75
 76	return bytes;
 77}
 78
 79static ssize_t efivarfs_file_read(struct file *file, char __user *userbuf,
 80		size_t count, loff_t *ppos)
 81{
 82	struct efivar_entry *var = file->private_data;
 83	unsigned long datasize = 0;
 84	u32 attributes;
 85	void *data;
 86	ssize_t size = 0;
 87	int err;
 88
 89	while (!__ratelimit(&file->f_cred->user->ratelimit))
 90		msleep(50);
 91
 92	err = efivar_entry_size(var, &datasize);
 93
 94	/*
 95	 * efivarfs represents uncommitted variables with
 96	 * zero-length files. Reading them should return EOF.
 97	 */
 98	if (err == -ENOENT)
 99		return 0;
100	else if (err)
101		return err;
102
103	data = kmalloc(datasize + sizeof(attributes), GFP_KERNEL);
104
105	if (!data)
106		return -ENOMEM;
107
108	size = efivar_entry_get(var, &attributes, &datasize,
109				data + sizeof(attributes));
110	if (size)
111		goto out_free;
112
113	memcpy(data, &attributes, sizeof(attributes));
114	size = simple_read_from_buffer(userbuf, count, ppos,
115				       data, datasize + sizeof(attributes));
116out_free:
117	kfree(data);
118
119	return size;
120}
121
122static int efivarfs_file_release(struct inode *inode, struct file *file)
123{
124	struct efivar_entry *var = inode->i_private;
125
126	inode_lock(inode);
127	var->removed = (--var->open_count == 0 && i_size_read(inode) == 0);
128	inode_unlock(inode);
129
130	if (var->removed)
131		simple_recursive_removal(file->f_path.dentry, NULL);
132
133	return 0;
134}
135
136static int efivarfs_file_open(struct inode *inode, struct file *file)
137{
138	struct efivar_entry *entry = inode->i_private;
139
140	file->private_data = entry;
141
142	inode_lock(inode);
143	entry->open_count++;
144	inode_unlock(inode);
145
146	return 0;
147}
148
149const struct file_operations efivarfs_file_operations = {
150	.open		= efivarfs_file_open,
151	.read		= efivarfs_file_read,
152	.write		= efivarfs_file_write,
153	.release	= efivarfs_file_release,
154};