umd: Remove usermode driver framework

#ifndef __LINUX_USERMODE_DRIVER_H__

#define __LINUX_USERMODE_DRIVER_H__

#include <linux/umh.h>

#include <linux/path.h>

struct umd_info {

	const char *driver_name;

	struct file *pipe_to_umh;

	struct file *pipe_from_umh;

	struct path wd;

	struct pid *tgid;

};

int umd_load_blob(struct umd_info *info, const void *data, size_t len);

int umd_unload_blob(struct umd_info *info);

int fork_usermode_driver(struct umd_info *info);

void umd_cleanup_helper(struct umd_info *info);

#endif /* __LINUX_USERMODE_DRIVER_H__ */

	    notifier.o ksysfs.o cred.o reboot.o \

	    async.o range.o smpboot.o ucount.o regset.o ksyms_common.o

obj-$(CONFIG_USERMODE_DRIVER) += usermode_driver.o

obj-$(CONFIG_MULTIUSER) += groups.o

obj-$(CONFIG_VHOST_TASK) += vhost_task.o

# SPDX-License-Identifier: GPL-2.0-only

config USERMODE_DRIVER

	bool

	default n

menuconfig BPF_PRELOAD

	bool "Preload BPF file system with kernel specific program and map iterators"

	depends on BPF

// 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)) {

		kern_unmount(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);

		kern_unmount(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);