aboutsummaryrefslogtreecommitdiffstats
path: root/kernel/usermode_driver.c
blob: 9dae1f6487136a3b9132c6f18c5c2aba2a028fc4 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
// SPDX-License-Identifier: GPL-2.0-only
/*
 * umd - User mode driver support
 */
#include <linux/shmem_fs.h>
#include <linux/pipe_fs_i.h>
#include <linux/mount.h>
#include <linux/fs_struct.h>
#include <linux/task_work.h>
#include <linux/usermode_driver.h>

static struct vfsmount *blob_to_mnt(const void *data, size_t len, const char *name)
{
	struct file_system_type *type;
	struct vfsmount *mnt;
	struct file *file;
	ssize_t written;
	loff_t pos = 0;

	type = get_fs_type("tmpfs");
	if (!type)
		return ERR_PTR(-ENODEV);

	mnt = kern_mount(type);
	put_filesystem(type);
	if (IS_ERR(mnt))
		return mnt;

	file = file_open_root_mnt(mnt, name, O_CREAT | O_WRONLY, 0700);
	if (IS_ERR(file)) {
		mntput(mnt);
		return ERR_CAST(file);
	}

	written = kernel_write(file, data, len, &pos);
	if (written != len) {
		int err = written;
		if (err >= 0)
			err = -ENOMEM;
		filp_close(file, NULL);
		mntput(mnt);
		return ERR_PTR(err);
	}

	fput(file);

	/* Flush delayed fput so exec can open the file read-only */
	flush_delayed_fput();
	task_work_run();
	return mnt;
}

/**
 * umd_load_blob - Remember a blob of bytes for fork_usermode_driver
 * @info: information about usermode driver
 * @data: a blob of bytes that can be executed as a file
 * @len:  The lentgh of the blob
 *
 */
int umd_load_blob(struct umd_info *info, const void *data, size_t len)
{
	struct vfsmount *mnt;

	if (WARN_ON_ONCE(info->wd.dentry || info->wd.mnt))
		return -EBUSY;

	mnt = blob_to_mnt(data, len, info->driver_name);
	if (IS_ERR(mnt))
		return PTR_ERR(mnt);

	info->wd.mnt = mnt;
	info->wd.dentry = mnt->mnt_root;
	return 0;
}
EXPORT_SYMBOL_GPL(umd_load_blob);

/**
 * umd_unload_blob - Disassociate @info from a previously loaded blob
 * @info: information about usermode driver
 *
 */
int umd_unload_blob(struct umd_info *info)
{
	if (WARN_ON_ONCE(!info->wd.mnt ||
			 !info->wd.dentry ||
			 info->wd.mnt->mnt_root != info->wd.dentry))
		return -EINVAL;

	kern_unmount(info->wd.mnt);
	info->wd.mnt = NULL;
	info->wd.dentry = NULL;
	return 0;
}
EXPORT_SYMBOL_GPL(umd_unload_blob);

static int umd_setup(struct subprocess_info *info, struct cred *new)
{
	struct umd_info *umd_info = info->data;
	struct file *from_umh[2];
	struct file *to_umh[2];
	int err;

	/* create pipe to send data to umh */
	err = create_pipe_files(to_umh, 0);
	if (err)
		return err;
	err = replace_fd(0, to_umh[0], 0);
	fput(to_umh[0]);
	if (err < 0) {
		fput(to_umh[1]);
		return err;
	}

	/* create pipe to receive data from umh */
	err = create_pipe_files(from_umh, 0);
	if (err) {
		fput(to_umh[1]);
		replace_fd(0, NULL, 0);
		return err;
	}
	err = replace_fd(1, from_umh[1], 0);
	fput(from_umh[1]);
	if (err < 0) {
		fput(to_umh[1]);
		replace_fd(0, NULL, 0);
		fput(from_umh[0]);
		return err;
	}

	set_fs_pwd(current->fs, &umd_info->wd);
	umd_info->pipe_to_umh = to_umh[1];
	umd_info->pipe_from_umh = from_umh[0];
	umd_info->tgid = get_pid(task_tgid(current));
	return 0;
}

static void umd_cleanup(struct subprocess_info *info)
{
	struct umd_info *umd_info = info->data;

	/* cleanup if umh_setup() was successful but exec failed */
	if (info->retval)
		umd_cleanup_helper(umd_info);
}

/**
 * umd_cleanup_helper - release the resources which were allocated in umd_setup
 * @info: information about usermode driver
 */
void umd_cleanup_helper(struct umd_info *info)
{
	fput(info->pipe_to_umh);
	fput(info->pipe_from_umh);
	put_pid(info->tgid);
	info->tgid = NULL;
}
EXPORT_SYMBOL_GPL(umd_cleanup_helper);

/**
 * fork_usermode_driver - fork a usermode driver
 * @info: information about usermode driver (shouldn't be NULL)
 *
 * Returns either negative error or zero which indicates success in
 * executing a usermode driver. In such case 'struct umd_info *info'
 * is populated with two pipes and a tgid of the process. The caller is
 * responsible for health check of the user process, killing it via
 * tgid, and closing the pipes when user process is no longer needed.
 */
int fork_usermode_driver(struct umd_info *info)
{
	struct subprocess_info *sub_info;
	const char *argv[] = { info->driver_name, NULL };
	int err;

	if (WARN_ON_ONCE(info->tgid))
		return -EBUSY;

	err = -ENOMEM;
	sub_info = call_usermodehelper_setup(info->driver_name,
					     (char **)argv, NULL, GFP_KERNEL,
					     umd_setup, umd_cleanup, info);
	if (!sub_info)
		goto out;

	err = call_usermodehelper_exec(sub_info, UMH_WAIT_EXEC);
out:
	return err;
}
EXPORT_SYMBOL_GPL(fork_usermode_driver);

Privacy Policy