On Thu, May 15 2025, Pasha Tatashin wrote:
> Introduce the user-space interface for the Live Update Orchestrator
> via ioctl commands, enabling external control over the live update
> process and management of preserved resources.
>
> Create a misc character device at /dev/liveupdate. Access
> to this device requires the CAP_SYS_ADMIN capability.
>
> A new UAPI header, <uapi/linux/liveupdate.h>, defines the necessary
> structures. The magic number is registered in
> Documentation/userspace-api/ioctl/ioctl-number.rst.
>
> Signed-off-by: Pasha Tatashin <pasha.tatashin@xxxxxxxxxx>
> ---
[...]
> +static int luo_ioctl_fd_preserve(struct liveupdate_fd *luo_fd)
> +{
> + struct file *file;
> + int ret;
> +
> + file = fget(luo_fd->fd);
> + if (!file) {
> + pr_err("Bad file descriptor\n");
> + return -EBADF;
> + }
> +
> + ret = luo_register_file(&luo_fd->token, file);
> + if (ret)
> + fput(file);
> +
> + return ret;
> +}
> +
> +static int luo_ioctl_fd_unpreserve(u64 token)
> +{
This leaks the refcount on the file that preserve took. Perhaps
luo_unregister_file() should return the file it unregistered, so this
can do fput(file)?
> + return luo_unregister_file(token);
> +}
> +
> +static int luo_ioctl_fd_restore(struct liveupdate_fd *luo_fd)
> +{
> + struct file *file;
> + int ret;
> + int fd;
> +
> + fd = get_unused_fd_flags(O_CLOEXEC);
> + if (fd < 0) {
> + pr_err("Failed to allocate new fd: %d\n", fd);
> + return fd;
> + }
> +
> + ret = luo_retrieve_file(luo_fd->token, &file);
> + if (ret < 0) {
> + put_unused_fd(fd);
> +
> + return ret;
> + }
> +
> + fd_install(fd, file);
> + luo_fd->fd = fd;
> +
> + return 0;
> +}
> +
> +static int luo_open(struct inode *inodep, struct file *filep)
> +{
> + if (!capable(CAP_SYS_ADMIN))
> + return -EACCES;
> +
> + if (filep->f_flags & O_EXCL)
> + return -EINVAL;
> +
> + return 0;
> +}
> +
> +static long luo_ioctl(struct file *filep, unsigned int cmd, unsigned long arg)
> +{
> + void __user *argp = (void __user *)arg;
> + struct liveupdate_fd luo_fd;
> + enum liveupdate_state state;
> + int ret = 0;
> + u64 token;
> +
> + if (_IOC_TYPE(cmd) != LIVEUPDATE_IOCTL_TYPE)
> + return -ENOTTY;
> +
> + switch (cmd) {
> + case LIVEUPDATE_IOCTL_GET_STATE:
> + state = READ_ONCE(luo_state);
> + if (copy_to_user(argp, &state, sizeof(luo_state)))
> + ret = -EFAULT;
> + break;
> +
> + case LIVEUPDATE_IOCTL_EVENT_PREPARE:
> + ret = luo_prepare();
> + break;
> +
> + case LIVEUPDATE_IOCTL_EVENT_FREEZE:
> + ret = luo_freeze();
> + break;
> +
> + case LIVEUPDATE_IOCTL_EVENT_FINISH:
> + ret = luo_finish();
> + break;
> +
> + case LIVEUPDATE_IOCTL_EVENT_CANCEL:
> + ret = luo_cancel();
> + break;
> +
> + case LIVEUPDATE_IOCTL_FD_PRESERVE:
> + if (copy_from_user(&luo_fd, argp, sizeof(luo_fd))) {
> + ret = -EFAULT;
> + break;
> + }
> +
> + ret = luo_ioctl_fd_preserve(&luo_fd);
> + if (!ret && copy_to_user(argp, &luo_fd, sizeof(luo_fd)))
> + ret = -EFAULT;
luo_unregister_file() is needed here on error.
> + break;
> +
> + case LIVEUPDATE_IOCTL_FD_UNPRESERVE:
> + if (copy_from_user(&token, argp, sizeof(u64))) {
> + ret = -EFAULT;
> + break;
> + }
> +
> + ret = luo_ioctl_fd_unpreserve(token);
> + break;
> +
> + case LIVEUPDATE_IOCTL_FD_RESTORE:
> + if (copy_from_user(&luo_fd, argp, sizeof(luo_fd))) {
> + ret = -EFAULT;
> + break;
> + }
> +
> + ret = luo_ioctl_fd_restore(&luo_fd);
> + if (!ret && copy_to_user(argp, &luo_fd, sizeof(luo_fd)))
> + ret = -EFAULT;
> + break;
> +
> + default:
> + pr_warn("ioctl: unknown command nr: 0x%x\n", _IOC_NR(cmd));
> + ret = -ENOTTY;
> + break;
> + }
> +
> + return ret;
> +}
[...]
--
Regards,
Pratyush Yadav
