1 /*
2  * Copyright (C) 2012 Red Hat, Inc.
3  * Copyright (C) 2012 Jeremy Kerr <jeremy.kerr@canonical.com>
4  *
5  * This program is free software; you can redistribute it and/or modify
6  * it under the terms of the GNU General Public License version 2 as
7  * published by the Free Software Foundation.
8  */
9 
10 #include <linux/efi.h>
11 #include <linux/delay.h>
12 #include <linux/fs.h>
13 #include <linux/slab.h>
14 #include <linux/mount.h>
15 
16 #include "internal.h"
17 
efivarfs_file_write(struct file * file,const char __user * userbuf,size_t count,loff_t * ppos)18 static ssize_t efivarfs_file_write(struct file *file,
19 		const char __user *userbuf, size_t count, loff_t *ppos)
20 {
21 	struct efivar_entry *var = file->private_data;
22 	void *data;
23 	u32 attributes;
24 	struct inode *inode = file->f_mapping->host;
25 	unsigned long datasize = count - sizeof(attributes);
26 	ssize_t bytes;
27 	bool set = false;
28 
29 	if (count < sizeof(attributes))
30 		return -EINVAL;
31 
32 	if (copy_from_user(&attributes, userbuf, sizeof(attributes)))
33 		return -EFAULT;
34 
35 	if (attributes & ~(EFI_VARIABLE_MASK))
36 		return -EINVAL;
37 
38 	data = memdup_user(userbuf + sizeof(attributes), datasize);
39 	if (IS_ERR(data))
40 		return PTR_ERR(data);
41 
42 	bytes = efivar_entry_set_get_size(var, attributes, &datasize,
43 					  data, &set);
44 	if (!set && bytes) {
45 		if (bytes == -ENOENT)
46 			bytes = -EIO;
47 		goto out;
48 	}
49 
50 	if (bytes == -ENOENT) {
51 		drop_nlink(inode);
52 		d_delete(file->f_path.dentry);
53 		dput(file->f_path.dentry);
54 	} else {
55 		inode_lock(inode);
56 		i_size_write(inode, datasize + sizeof(attributes));
57 		inode_unlock(inode);
58 	}
59 
60 	bytes = count;
61 
62 out:
63 	kfree(data);
64 
65 	return bytes;
66 }
67 
efivarfs_file_read(struct file * file,char __user * userbuf,size_t count,loff_t * ppos)68 static ssize_t efivarfs_file_read(struct file *file, char __user *userbuf,
69 		size_t count, loff_t *ppos)
70 {
71 	struct efivar_entry *var = file->private_data;
72 	unsigned long datasize = 0;
73 	u32 attributes;
74 	void *data;
75 	ssize_t size = 0;
76 	int err;
77 
78 	while (!__ratelimit(&file->f_cred->user->ratelimit)) {
79 		if (!msleep_interruptible(50))
80 			return -EINTR;
81 	}
82 
83 	err = efivar_entry_size(var, &datasize);
84 
85 	/*
86 	 * efivarfs represents uncommitted variables with
87 	 * zero-length files. Reading them should return EOF.
88 	 */
89 	if (err == -ENOENT)
90 		return 0;
91 	else if (err)
92 		return err;
93 
94 	data = kmalloc(datasize + sizeof(attributes), GFP_KERNEL);
95 
96 	if (!data)
97 		return -ENOMEM;
98 
99 	size = efivar_entry_get(var, &attributes, &datasize,
100 				data + sizeof(attributes));
101 	if (size)
102 		goto out_free;
103 
104 	memcpy(data, &attributes, sizeof(attributes));
105 	size = simple_read_from_buffer(userbuf, count, ppos,
106 				       data, datasize + sizeof(attributes));
107 out_free:
108 	kfree(data);
109 
110 	return size;
111 }
112 
113 static int
efivarfs_ioc_getxflags(struct file * file,void __user * arg)114 efivarfs_ioc_getxflags(struct file *file, void __user *arg)
115 {
116 	struct inode *inode = file->f_mapping->host;
117 	unsigned int i_flags;
118 	unsigned int flags = 0;
119 
120 	i_flags = inode->i_flags;
121 	if (i_flags & S_IMMUTABLE)
122 		flags |= FS_IMMUTABLE_FL;
123 
124 	if (copy_to_user(arg, &flags, sizeof(flags)))
125 		return -EFAULT;
126 	return 0;
127 }
128 
129 static int
efivarfs_ioc_setxflags(struct file * file,void __user * arg)130 efivarfs_ioc_setxflags(struct file *file, void __user *arg)
131 {
132 	struct inode *inode = file->f_mapping->host;
133 	unsigned int flags;
134 	unsigned int i_flags = 0;
135 	int error;
136 
137 	if (!inode_owner_or_capable(inode))
138 		return -EACCES;
139 
140 	if (copy_from_user(&flags, arg, sizeof(flags)))
141 		return -EFAULT;
142 
143 	if (flags & ~FS_IMMUTABLE_FL)
144 		return -EOPNOTSUPP;
145 
146 	if (!capable(CAP_LINUX_IMMUTABLE))
147 		return -EPERM;
148 
149 	if (flags & FS_IMMUTABLE_FL)
150 		i_flags |= S_IMMUTABLE;
151 
152 
153 	error = mnt_want_write_file(file);
154 	if (error)
155 		return error;
156 
157 	inode_lock(inode);
158 	inode_set_flags(inode, i_flags, S_IMMUTABLE);
159 	inode_unlock(inode);
160 
161 	mnt_drop_write_file(file);
162 
163 	return 0;
164 }
165 
166 static long
efivarfs_file_ioctl(struct file * file,unsigned int cmd,unsigned long p)167 efivarfs_file_ioctl(struct file *file, unsigned int cmd, unsigned long p)
168 {
169 	void __user *arg = (void __user *)p;
170 
171 	switch (cmd) {
172 	case FS_IOC_GETFLAGS:
173 		return efivarfs_ioc_getxflags(file, arg);
174 	case FS_IOC_SETFLAGS:
175 		return efivarfs_ioc_setxflags(file, arg);
176 	}
177 
178 	return -ENOTTY;
179 }
180 
181 const struct file_operations efivarfs_file_operations = {
182 	.open	= simple_open,
183 	.read	= efivarfs_file_read,
184 	.write	= efivarfs_file_write,
185 	.llseek	= no_llseek,
186 	.unlocked_ioctl = efivarfs_file_ioctl,
187 };
188