On Mon, Mar 16, 2015 at 06:40:59PM +0200, Pavel Boldin wrote:
> From: Pavel Boldin <pboldin at mirantis.com>
>
> The `eventfd_link' module provides an API to "steal" fd from another
> process had been written with a bug that leaks `struct file' because of the
> extra reference counter increment and missing `fput' call.
>
> The other bug is using another process' `task_struct' without incrementing
> a reference counter.
>
> Fix these bugs and refactor the module.
> ---
> examples/vhost/eventfd_link/eventfd_link.c | 236
> ++++++++++++++++-------------
> 1 file changed, 130 insertions(+), 106 deletions(-)
>
> diff --git a/examples/vhost/eventfd_link/eventfd_link.c
> b/examples/vhost/eventfd_link/eventfd_link.c
> index 69470ba..9f1f8fb 100644
> --- a/examples/vhost/eventfd_link/eventfd_link.c
> +++ b/examples/vhost/eventfd_link/eventfd_link.c
> @@ -42,15 +42,15 @@
> * get_files_struct is copied from fs/file.c
> */
> struct files_struct *
> -get_files_struct (struct task_struct *task)
> +get_files_struct(struct task_struct *task)
> {
> struct files_struct *files;
>
> - task_lock (task);
> + task_lock(task);
> files = task->files;
> if (files)
> - atomic_inc (&files->count);
> - task_unlock (task);
> + atomic_inc(&files->count);
> + task_unlock(task);
>
> return files;
> }
> @@ -59,117 +59,142 @@ get_files_struct (struct task_struct *task)
> * put_files_struct is extracted from fs/file.c
> */
> void
> -put_files_struct (struct files_struct *files)
> +put_files_struct(struct files_struct *files)
> {
> - if (atomic_dec_and_test (&files->count))
> - {
> + if (atomic_dec_and_test(&files->count))
> BUG ();
> +}
> +
> +static struct file *
> +fget_from_files(struct files_struct *files, unsigned fd)
> +{
> + struct file *file;
> +
> + rcu_read_lock();
> + file = fcheck_files(files, fd);
> + if (file)
> + {
> + if (file->f_mode & FMODE_PATH
> + || !atomic_long_inc_not_zero(&file->f_count))
> + file = NULL;
> }
> + rcu_read_unlock();
> +
> + return file;
> +}
> +
> +static int
> +close_fd(unsigned fd)
> +{
> + struct file *file;
> + struct files_struct *files = current->files;
> + struct fdtable *fdt;
> +
> + spin_lock(&files->file_lock);
> + fdt = files_fdtable(files);
> + if (fd >= fdt->max_fds)
> + goto out_unlock;
> + file = fdt->fd[fd];
> + if (!file)
> + goto out_unlock;
> + rcu_assign_pointer(fdt->fd[fd], NULL);
> + __clear_bit(fd, fdt->close_on_exec);
> + spin_unlock(&files->file_lock);
> + return filp_close(file, files);
> +
> +out_unlock:
> + spin_unlock(&files->file_lock);
> + return -EBADF;
> }
>
>
> static long
> -eventfd_link_ioctl (struct file *f, unsigned int ioctl, unsigned long arg)
> +eventfd_link_ioctl_copy(unsigned long arg)
> {
> - void __user *argp = (void __user *) arg;
> + long ret = -EFAULT;
> struct task_struct *task_target = NULL;
> - struct file *file;
> - struct files_struct *files;
> - struct fdtable *fdt;
> + struct file *target_file = NULL;
> + struct files_struct *target_files = NULL;
> struct eventfd_copy eventfd_copy;
> + struct pid *pid;
> +
> + if (copy_from_user(&eventfd_copy, (void __user*)arg,
> + sizeof(struct eventfd_copy)))
> + goto out;
> +
> + /*
> + * Find the task struct for the target pid
> + */
> + pid = find_vpid(eventfd_copy.target_pid);
> + if (pid == NULL) {
> + printk(KERN_INFO "Unable to find pid %d\n",
> + eventfd_copy.target_pid);
> + goto out;
> + }
> +
> + task_target = get_pid_task(pid, PIDTYPE_PID);
> + if (task_target == NULL) {
> + printk(KERN_INFO "Failed to get task for pid %d\n",
> + eventfd_copy.target_pid);
> + goto out;
> + }
> +
> + ret = close_fd(eventfd_copy.source_fd);
> + if (ret)
> + goto out_task;
> + ret = -EFAULT;
> +
> + /*
> + * Find the file struct associated with the target fd.
> + */
> +
> + target_files = get_files_struct(task_target);
> + if (target_files == NULL) {
> + printk (KERN_INFO "Failed to get target files struct\n");
> + goto out_task;
> + }
> +
> + target_file = fget_from_files(target_files, eventfd_copy.target_fd);
> +
> + if (target_file == NULL) {
> + printk (KERN_INFO "Failed to get file from target pid\n");
> + goto out_target_files;
> + }
> +
> +
> + /*
> + * Install the file struct from the target process into the
> + * file desciptor of the source process,
> + */
> +
> + fd_install(eventfd_copy.source_fd, target_file);
> +
> + ret = 0;
> +
> +out_target_files:
> + put_files_struct(target_files);
> +out_task:
> + put_task_struct(task_target);
> +out:
> + return ret;
> +}
> +
> +static long
> +eventfd_link_ioctl(struct file *f, unsigned int ioctl, unsigned long arg)
> +{
> + long ret;
>
> switch (ioctl)
> {
> case EVENTFD_COPY:
> - if (copy_from_user (&eventfd_copy, argp, sizeof (struct
> eventfd_copy)))
> - return -EFAULT;
> -
> - /*
> - * Find the task struct for the target pid
> - */
> - task_target =
> - pid_task (find_vpid (eventfd_copy.target_pid),
> PIDTYPE_PID);
> - if (task_target == NULL)
> - {
> - printk (KERN_DEBUG "Failed to get mem ctx for
> target pid\n");
> - return -EFAULT;
> - }
> -
> - files = get_files_struct (current);
> - if (files == NULL)
> - {
> - printk (KERN_DEBUG "Failed to get files
> struct\n");
> - return -EFAULT;
> - }
> -
> - rcu_read_lock ();
> - file = fcheck_files (files, eventfd_copy.source_fd);
> - if (file)
> - {
> - if (file->f_mode & FMODE_PATH
> - || !atomic_long_inc_not_zero
> (&file->f_count))
> - file = NULL;
> - }
> - rcu_read_unlock ();
> - put_files_struct (files);
> -
> - if (file == NULL)
> - {
> - printk (KERN_DEBUG "Failed to get file from
> source pid\n");
> - return 0;
> - }
> -
> - /*
> - * Release the existing eventfd in the source process
> - */
> - spin_lock (&files->file_lock);
> - fput(file);
> - filp_close (file, files);
> - fdt = files_fdtable (files);
> - fdt->fd[eventfd_copy.source_fd] = NULL;
> - spin_unlock (&files->file_lock);
> -
> - /*
> - * Find the file struct associated with the target fd.
> - */
> -
> - files = get_files_struct (task_target);
> - if (files == NULL)
> - {
> - printk (KERN_DEBUG "Failed to get files
> struct\n");
> - return -EFAULT;
> - }
> -
> - rcu_read_lock ();
> - file = fcheck_files (files, eventfd_copy.target_fd);
> - if (file)
> - {
> - if (file->f_mode & FMODE_PATH
> - || !atomic_long_inc_not_zero
> (&file->f_count))
> - file = NULL;
> - }
> - rcu_read_unlock ();
> - put_files_struct (files);
> -
> - if (file == NULL)
> - {
> - printk (KERN_DEBUG "Failed to get file from
> target pid\n");
> - return 0;
> - }
> -
> -
> - /*
> - * Install the file struct from the target process into
> the
> - * file desciptor of the source process,
> - */
> -
> - fd_install (eventfd_copy.source_fd, file);
> -
> - return 0;
> -
> + ret = eventfd_link_ioctl_copy(arg);
> + break;
> default:
> - return -ENOIOCTLCMD;
> + ret = -ENOIOCTLCMD;
> + break;
> }
> +
> + return ret;
> }
>
> static const struct file_operations eventfd_link_fops = {
> @@ -184,21 +209,20 @@ static struct miscdevice eventfd_link_misc = {
> };
>
> static int __init
> -eventfd_link_init (void)
> +eventfd_link_init(void)
> {
> - printk(KERN_INFO "eventfd_link is broken, use it at your risk\n");
> - return misc_register (&eventfd_link_misc);
> + return misc_register(&eventfd_link_misc);
> }
>
> -module_init (eventfd_link_init);
> +module_init(eventfd_link_init);
>
> static void __exit
> -eventfd_link_exit (void)
> +eventfd_link_exit(void)
> {
> - misc_deregister (&eventfd_link_misc);
> + misc_deregister(&eventfd_link_misc);
> }
>
> -module_exit (eventfd_link_exit);
> +module_exit(eventfd_link_exit);
>
> MODULE_VERSION ("0.0.1");
> MODULE_LICENSE ("GPL v2");
> --
> 1.9.1
>
>
You need to respin this. This library has since moved to another location in
the tree
Neil
