Oleg Nesterov wrote:
> sys_setsid() still deals with pid_t's from the global namespace. This means
> that the "session > 1" check can't help for sub-namespace init, setsid() can't
> succeed because copy_process(CLONE_NEWPID) populates PIDTYPE_PGID/SID links.
>
> Remove the usage of task_struct->pid and convert the code to use "struct pid".
> This also simplifies and speedups the code, saves one find_pid().
>
> Signed-off-by: Oleg Nesterov <[email protected]>
Acked-by: Pavel Emelyanov <[email protected]>
> --- PT/kernel/sys.c~1_setsid 2007-11-26 15:52:15.000000000 +0300
> +++ PT/kernel/sys.c 2007-11-26 16:10:43.000000000 +0300
> @@ -1045,35 +1045,33 @@ asmlinkage long sys_getsid(pid_t pid)
> asmlinkage long sys_setsid(void)
> {
> struct task_struct *group_leader = current->group_leader;
> - pid_t session;
> + struct pid *sid = task_pid(group_leader);
> + pid_t session = pid_vnr(sid);
> int err = -EPERM;
>
> write_lock_irq(&tasklist_lock);
> -
> /* Fail if I am already a session leader */
> if (group_leader->signal->leader)
> goto out;
>
> - session = group_leader->pid;
> - /* Fail if a process group id already exists that equals the
> - * proposed session id.
> + /* Fail if a process group id already exists that equals the proposed
> + * session id.
> *
> - * Don't check if session id == 1 because kernel threads use this
> - * session id and so the check will always fail and make it so
> - * init cannot successfully call setsid.
> + * Don't check if session == 1 because kernel threads and CLONE_NEWPID
> + * tasks use this session id and so the check will always fail and make
> + * it so init cannot successfully call setsid.
> */
> - if (session > 1 && find_task_by_pid_type_ns(PIDTYPE_PGID,
> - session, &init_pid_ns))
> + if (session != 1 && pid_task(sid, PIDTYPE_PGID))
> goto out;
>
> group_leader->signal->leader = 1;
> - __set_special_pids(session, session);
> + __set_special_pids(pid_nr(sid), pid_nr(sid));
>
> spin_lock(&group_leader->sighand->siglock);
> group_leader->signal->tty = NULL;
> spin_unlock(&group_leader->sighand->siglock);
>
> - err = task_pgrp_vnr(group_leader);
> + err = session;
> out:
> write_unlock_irq(&tasklist_lock);
> return err;
>
>
-
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