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
12 static 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 */
60 int 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 }
75 EXPORT_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 */
82 int 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 }
94 EXPORT_SYMBOL_GPL(umd_unload_blob);
95
96 static 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
137 static 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 */
150 void 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 }
157 EXPORT_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 */
169 int 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);
186 out:
187 return err;
188 }
189 EXPORT_SYMBOL_GPL(fork_usermode_driver);
190
191
192
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