Re: [RFC 12/12][PATCH] SCHED_DEADLINE: modified sched_*_ex API

[Peter Zijlstra <peterz@infradead.org>]

On Fri, 2009-10-16 at 17:48 +0200, Raistlin wrote:
> @@ -6807,9 +6811,10 @@ out_unlock:
>  /**
>   * sys_sched_getparam - get the DEADLINE task parameters of a thread
>   * @pid: the pid in question.
> + * @len: size of data pointed by param_ex.
>   * @param_ex: structure containing the new parameters (deadline, runtime, etc.).
>   */
> -SYSCALL_DEFINE2(sched_getparam_ex, pid_t, pid,
> +SYSCALL_DEFINE3(sched_getparam_ex, pid_t, pid, unsigned, len,
>                 struct sched_param_ex __user *, param_ex)
>  {
>         struct sched_param_ex lp;
> @@ -6818,6 +6823,8 @@ SYSCALL_DEFINE2(sched_getparam_ex, pid_t, pid,
>  
>         if (!param_ex || pid < 0)
>                 return -EINVAL;
> +       if (len < sizeof(struct sched_param_ex))
> +               return -EINVAL;
>  
>         read_lock(&tasklist_lock);
>         p = find_process_by_pid(pid);

This allows len > sizeof().

> @@ -6837,7 +6844,7 @@ SYSCALL_DEFINE2(sched_getparam_ex, pid_t, pid,
>         /*
>          * This one might sleep, we cannot do it with a spinlock held ...
>          */
> -       retval = copy_to_user(param_ex, &lp, sizeof(*param_ex)) ? -EFAULT : 0;
> +       retval = copy_to_user(param_ex, &lp, len) ? -EFAULT : 0;
>  
>         return retval; 

Which would copy more than lp, resulting in a stack leak, right?