1 // SPDX-License-Identifier: GPL-2.0-only
3 * umd - User mode driver support
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>
12 static struct vfsmount
*blob_to_mnt(const void *data
, size_t len
, const char *name
)
14 struct file_system_type
*type
;
20 type
= get_fs_type("tmpfs");
22 return ERR_PTR(-ENODEV
);
24 mnt
= kern_mount(type
);
29 file
= file_open_root(mnt
->mnt_root
, mnt
, name
, O_CREAT
| O_WRONLY
, 0700);
32 return ERR_CAST(file
);
35 written
= kernel_write(file
, data
, len
, &pos
);
40 filp_close(file
, NULL
);
47 /* Flush delayed fput so exec can open the file read-only */
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
60 int umd_load_blob(struct umd_info
*info
, const void *data
, size_t len
)
64 if (WARN_ON_ONCE(info
->wd
.dentry
|| info
->wd
.mnt
))
67 mnt
= blob_to_mnt(data
, len
, info
->driver_name
);
72 info
->wd
.dentry
= mnt
->mnt_root
;
75 EXPORT_SYMBOL_GPL(umd_load_blob
);
78 * umd_unload_blob - Disassociate @info from a previously loaded blob
79 * @info: information about usermode driver
82 int umd_unload_blob(struct umd_info
*info
)
84 if (WARN_ON_ONCE(!info
->wd
.mnt
||
86 info
->wd
.mnt
->mnt_root
!= info
->wd
.dentry
))
89 kern_unmount(info
->wd
.mnt
);
91 info
->wd
.dentry
= NULL
;
94 EXPORT_SYMBOL_GPL(umd_unload_blob
);
96 static int umd_setup(struct subprocess_info
*info
, struct cred
*new)
98 struct umd_info
*umd_info
= info
->data
;
99 struct file
*from_umh
[2];
100 struct file
*to_umh
[2];
103 /* create pipe to send data to umh */
104 err
= create_pipe_files(to_umh
, 0);
107 err
= replace_fd(0, to_umh
[0], 0);
114 /* create pipe to receive data from umh */
115 err
= create_pipe_files(from_umh
, 0);
118 replace_fd(0, NULL
, 0);
121 err
= replace_fd(1, from_umh
[1], 0);
125 replace_fd(0, NULL
, 0);
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
));
137 static void umd_cleanup(struct subprocess_info
*info
)
139 struct umd_info
*umd_info
= info
->data
;
141 /* cleanup if umh_setup() was successful but exec failed */
143 fput(umd_info
->pipe_to_umh
);
144 fput(umd_info
->pipe_from_umh
);
145 put_pid(umd_info
->tgid
);
146 umd_info
->tgid
= NULL
;
151 * fork_usermode_driver - fork a usermode driver
152 * @info: information about usermode driver (shouldn't be NULL)
154 * Returns either negative error or zero which indicates success in
155 * executing a usermode driver. In such case 'struct umd_info *info'
156 * is populated with two pipes and a tgid of the process. The caller is
157 * responsible for health check of the user process, killing it via
158 * tgid, and closing the pipes when user process is no longer needed.
160 int fork_usermode_driver(struct umd_info
*info
)
162 struct subprocess_info
*sub_info
;
163 const char *argv
[] = { info
->driver_name
, NULL
};
166 if (WARN_ON_ONCE(info
->tgid
))
170 sub_info
= call_usermodehelper_setup(info
->driver_name
,
171 (char **)argv
, NULL
, GFP_KERNEL
,
172 umd_setup
, umd_cleanup
, info
);
176 err
= call_usermodehelper_exec(sub_info
, UMH_WAIT_EXEC
);
180 EXPORT_SYMBOL_GPL(fork_usermode_driver
);