On 06/01, Tycho Andersen wrote:
>
> --- a/include/linux/seccomp.h
> +++ b/include/linux/seccomp.h
> @@ -25,6 +25,9 @@ struct seccomp_filter;
> struct seccomp {
> int mode;
> struct seccomp_filter *filter;
> +#ifdef CONFIG_CHECKPOINT_RESTORE
> + bool suspended;
> +#endif
Then afaics you need to change copy_seccomp() to clear ->suspended.
At least if the child is not traced.
> @@ -691,6 +697,11 @@ u32 seccomp_phase1(struct seccomp_data *sd)
> int this_syscall = sd ? sd->nr :
> syscall_get_nr(current, task_pt_regs(current));
>
> +#ifdef CONFIG_CHECKPOINT_RESTORE
> + if (unlikely(current->seccomp.suspended))
> + return SECCOMP_PHASE1_OK;
> +#endif
> +
I am wondering if PTRACE_SUSPEND_SECCOMP can just clear/set TIF_SECCOMP.
Of course, it is not that resume_seccomp() can simply do set_tsk_thread_flag,
it should be more careful. And prctl_set_seccomp() paths will need some
changes. Probably not, this would be more complex.
So perhaps it would be better to add PTRACE_O_SUSPEND_SECCOMP? This also
solves the problem with the killed tracer. Except TIF_NOTSC...
But why do we bother to play with TIF_NOTSC, could you explain?
> +int suspend_seccomp(struct task_struct *task)
> +{
> + int ret = -EACCES;
> +
> + spin_lock_irq(&task->sighand->siglock);
> +
> + if (!capable(CAP_SYS_ADMIN))
> + goto out;
I am puzzled ;) Why do we need ->siglock? And even if we need it, why
we can't check CAP_SYS_ADMIN lockless?
And I am not sure I understand why do we need the additional security
check, but I leave this to you and Andy.
If you have the rights to trace this task, then you can do anything
the tracee could do without the filtering.
> +
> + task->seccomp.suspended = true;
> +
> +#ifdef TIF_NOTSC
> + if (task->seccomp.mode == SECCOMP_MODE_STRICT)
> + clear_tsk_thread_flag(task, TIF_NOTSC);
> +#endif
> +
> + ret = 0;
> +out:
> + spin_unlock_irq(&task->sighand->siglock);
> +
> + return ret;
> +}
> +
> +int resume_seccomp(struct task_struct *task)
> +{
> + int ret = -EACCES;
> +
> + spin_lock_irq(&task->sighand->siglock);
> +
> + if (!capable(CAP_SYS_ADMIN))
> + goto out;
> +
> + task->seccomp.suspended = false;
> +
> +#ifdef TIF_NOTSC
> + if (task->seccomp.mode == SECCOMP_MODE_STRICT)
> + set_tsk_thread_flag(task, TIF_NOTSC);
> +#endif
> +
> + ret = 0;
> +out:
> + spin_unlock_irq(&task->sighand->siglock);
> +
> + return ret;
> +}
> +#endif /* CONFIG_CHECKPOINT_RESTORE */
Well, I do not think we need 2 helpers, just one which takes a boolean
will look better, imo.
Oleg.
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