1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * umd - User mode driver support
4 */
5#include <linux/shmem_fs.h>
6#include <linux/pipe_fs_i.h>
7#include <linux/mount.h>
8#include <linux/fs_struct.h>
9#include <linux/task_work.h>
10#include <linux/usermode_driver.h>
11
12static struct vfsmount *blob_to_mnt(const void *data, size_t len, const char *name)
13{
14	struct file_system_type *type;
15	struct vfsmount *mnt;
16	struct file *file;
17	ssize_t written;
18	loff_t pos = 0;
19
20	type = get_fs_type("tmpfs");
21	if (!type)
22		return ERR_PTR(-ENODEV);
23
24	mnt = kern_mount(type);
25	put_filesystem(type);
26	if (IS_ERR(mnt))
27		return mnt;
28
29	file = file_open_root_mnt(mnt, name, O_CREAT | O_WRONLY, 0700);
30	if (IS_ERR(file)) {
31		kern_unmount(mnt);
32		return ERR_CAST(file);
33	}
34
35	written = kernel_write(file, data, len, &pos);
36	if (written != len) {
37		int err = written;
38		if (err >= 0)
39			err = -ENOMEM;
40		filp_close(file, NULL);
41		kern_unmount(mnt);
42		return ERR_PTR(err);
43	}
44
45	fput(file);
46
47	/* Flush delayed fput so exec can open the file read-only */
48	flush_delayed_fput();
49	task_work_run();
50	return mnt;
51}
52
53/**
54 * umd_load_blob - Remember a blob of bytes for fork_usermode_driver
55 * @info: information about usermode driver
56 * @data: a blob of bytes that can be executed as a file
57 * @len:  The lentgh of the blob
58 *
59 */
60int umd_load_blob(struct umd_info *info, const void *data, size_t len)
61{
62	struct vfsmount *mnt;
63
64	if (WARN_ON_ONCE(info->wd.dentry || info->wd.mnt))
65		return -EBUSY;
66
67	mnt = blob_to_mnt(data, len, info->driver_name);
68	if (IS_ERR(mnt))
69		return PTR_ERR(mnt);
70
71	info->wd.mnt = mnt;
72	info->wd.dentry = mnt->mnt_root;
73	return 0;
74}
75EXPORT_SYMBOL_GPL(umd_load_blob);
76
77/**
78 * umd_unload_blob - Disassociate @info from a previously loaded blob
79 * @info: information about usermode driver
80 *
81 */
82int umd_unload_blob(struct umd_info *info)
83{
84	if (WARN_ON_ONCE(!info->wd.mnt ||
85			 !info->wd.dentry ||
86			 info->wd.mnt->mnt_root != info->wd.dentry))
87		return -EINVAL;
88
89	kern_unmount(info->wd.mnt);
90	info->wd.mnt = NULL;
91	info->wd.dentry = NULL;
92	return 0;
93}
94EXPORT_SYMBOL_GPL(umd_unload_blob);
95
96static int umd_setup(struct subprocess_info *info, struct cred *new)
97{
98	struct umd_info *umd_info = info->data;
99	struct file *from_umh[2];
100	struct file *to_umh[2];
101	int err;
102
103	/* create pipe to send data to umh */
104	err = create_pipe_files(to_umh, 0);
105	if (err)
106		return err;
107	err = replace_fd(0, to_umh[0], 0);
108	fput(to_umh[0]);
109	if (err < 0) {
110		fput(to_umh[1]);
111		return err;
112	}
113
114	/* create pipe to receive data from umh */
115	err = create_pipe_files(from_umh, 0);
116	if (err) {
117		fput(to_umh[1]);
118		replace_fd(0, NULL, 0);
119		return err;
120	}
121	err = replace_fd(1, from_umh[1], 0);
122	fput(from_umh[1]);
123	if (err < 0) {
124		fput(to_umh[1]);
125		replace_fd(0, NULL, 0);
126		fput(from_umh[0]);
127		return err;
128	}
129
130	set_fs_pwd(current->fs, &umd_info->wd);
131	umd_info->pipe_to_umh = to_umh[1];
132	umd_info->pipe_from_umh = from_umh[0];
133	umd_info->tgid = get_pid(task_tgid(current));
134	return 0;
135}
136
137static void umd_cleanup(struct subprocess_info *info)
138{
139	struct umd_info *umd_info = info->data;
140
141	/* cleanup if umh_setup() was successful but exec failed */
142	if (info->retval)
143		umd_cleanup_helper(umd_info);
144}
145
146/**
147 * umd_cleanup_helper - release the resources which were allocated in umd_setup
148 * @info: information about usermode driver
149 */
150void umd_cleanup_helper(struct umd_info *info)
151{
152	fput(info->pipe_to_umh);
153	fput(info->pipe_from_umh);
154	put_pid(info->tgid);
155	info->tgid = NULL;
156}
157EXPORT_SYMBOL_GPL(umd_cleanup_helper);
158
159/**
160 * fork_usermode_driver - fork a usermode driver
161 * @info: information about usermode driver (shouldn't be NULL)
162 *
163 * Returns either negative error or zero which indicates success in
164 * executing a usermode driver. In such case 'struct umd_info *info'
165 * is populated with two pipes and a tgid of the process. The caller is
166 * responsible for health check of the user process, killing it via
167 * tgid, and closing the pipes when user process is no longer needed.
168 */
169int fork_usermode_driver(struct umd_info *info)
170{
171	struct subprocess_info *sub_info;
172	const char *argv[] = { info->driver_name, NULL };
173	int err;
174
175	if (WARN_ON_ONCE(info->tgid))
176		return -EBUSY;
177
178	err = -ENOMEM;
179	sub_info = call_usermodehelper_setup(info->driver_name,
180					     (char **)argv, NULL, GFP_KERNEL,
181					     umd_setup, umd_cleanup, info);
182	if (!sub_info)
183		goto out;
184
185	err = call_usermodehelper_exec(sub_info, UMH_WAIT_EXEC);
186out:
187	return err;
188}
189EXPORT_SYMBOL_GPL(fork_usermode_driver);
190
191
192