linux-kernel - Re: [PATCH] ptrace: add ability to get/set signal-blocked mask

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Date:	Mon, 22 Apr 2013 17:07:10 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Andrey Vagin <avagin@...nvz.org>
Cc:	linux-kernel@...r.kernel.org, Roland McGrath <roland@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Michael Kerrisk <mtk.manpages@...il.com>,
	Pavel Emelyanov <xemul@...allels.com>,
	Cyrill Gorcunov <gorcunov@...nvz.org>
Subject: Re: [PATCH] ptrace: add ability to get/set signal-blocked mask

On 04/22, Oleg Nesterov wrote:
>
> On 04/22, Andrey Vagin wrote:
> >
> > +	case PTRACE_SETSIGMASK:
> > +	{
> > +		sigset_t new_set;
> > +
> > +		if (addr != sizeof(sigset_t)) {
> > +			ret = -EINVAL;
> > +			break;
> > +		}
> > +
> > +		if (copy_from_user(&new_set, datavp, sizeof(sigset_t))) {
> > +			ret = -EFAULT;
> > +			break;
> > +		}
> > +
> > +		sigdelsetmask(&new_set, sigmask(SIGKILL)|sigmask(SIGSTOP));
> > +
> > +		spin_lock_irq(&child->sighand->siglock);
> > +		__set_task_blocked(child, &new_set);
> > +		spin_unlock_irq(&child->sighand->siglock);
>
> No, please don't...
>
> set_current_blocked/__set_task_blocked assume that tsk == current.
> If nothing else, note recalc_sigpending() in __set_task_blocked().
>
> I don't understand "This method is not suitable for stopped tasks"
> from the changelog, but if you really need PTRACE_SETSIGMASK just
> change ->blocked under siglock and do recalc_sigpending_tsk(child).
                                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

actually this is not necessary, the tracee will do recalc_sigpending()
after resume. But perhaps a comment make sense.

Oleg.

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