On 05/04, Eric W. Biederman wrote:
>
> Cc'd Oleg as he tends to be deeply involved with this class of locking.
>
> Mateusz Guzik <mgu...@redhat.com> writes:
>
> > proc_pid_limits takes ->sighand lock prior to accessing rlimits, but it
> > serves no purpose as it does not prevent modifications.
Well. I agree this all needs cleanups or at least additional comments, but
> > @@ -618,14 +618,12 @@ static int proc_pid_limits(struct seq_file *m, struct
> > pid_namespace *ns,
> > struct pid *pid, struct task_struct *task)
> > {
> > unsigned int i;
> > - unsigned long flags;
> >
> > struct rlimit rlim[RLIM_NLIMITS];
> >
> > - if (!lock_task_sighand(task, &flags))
> > - return 0;
> > + task_lock(task->group_leader);
This is already unsafe. ->group_leader can point to nowhere if this threads
exits. lock_task_sighand() ensures that this can't happen.
> > - /* protect tsk->signal and tsk->sighand from disappearing */
> > - read_lock(&tasklist_lock);
> > - if (!tsk->sighand) {
> > - retval = -ESRCH;
> > - goto out;
> > + task_lock(tsk->group_leader);
The same, but yes the comment is misleading.
Oleg.
