[PATCH v8 3/9] seccomp: introduce writer locking

[Kees Cook]

On Wed, Jun 25, 2014 at 11:07 AM, Oleg Nesterov <oleg at redhat.com> wrote:
> On 06/24, Kees Cook wrote:
>>
>> +static void copy_seccomp(struct task_struct *p)
>> +{
>> +#ifdef CONFIG_SECCOMP
>> +     /*
>> +      * Must be called with sighand->lock held, which is common to
>> +      * all threads in the group. Regardless, nothing special is
>> +      * needed for the child since it is not yet in the tasklist.
>> +      */
>> +     BUG_ON(!spin_is_locked(&current->sighand->siglock));
>> +
>> +     get_seccomp_filter(current);
>> +     p->seccomp = current->seccomp;
>> +
>> +     if (p->seccomp.mode != SECCOMP_MODE_DISABLED)
>> +             set_tsk_thread_flag(p, TIF_SECCOMP);
>> +#endif
>> +}
>
> Wait. But what about no_new_privs? We should copy it as well...
>
> Perhaps this helper should be updated a bit and moved into seccomp.c so
> that seccomp_sync_threads() could use it too.

Ah! Yes. I had been thinking it had been copied during the task_struct
duplication, but that would have been before holding sighand->lock, so
it needs explicit recopying. Thanks!

-Kees

-- 
Kees Cook
Chrome OS Security