usermode_driver.c (4454B)
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