linux-kernel - Re: [PATCH] ptrace: take into account saved_sigmask in PTRACE

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Message-ID: <20181122114751.GA28270@redhat.com>
Date:   Thu, 22 Nov 2018 12:47:52 +0100
From:   Oleg Nesterov <oleg@...hat.com>
To:     Andrei Vagin <avagin@...il.com>
Cc:     linux-kernel@...r.kernel.org,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] ptrace: take into account saved_sigmask in
 PTRACE_{GET,SET}SIGMASK

On 11/19, Andrei Vagin wrote:
>
>  	case PTRACE_SETSIGMASK: {
>  		sigset_t new_set;
> @@ -962,6 +971,8 @@ int ptrace_request(struct task_struct *child, long request,
>  		child->blocked = new_set;
>  		spin_unlock_irq(&child->sighand->siglock);
>
> +		clear_tsk_restore_sigmask(child);
> +

I am not sure I understand this change...

I forgot everything I knew about criu, but iiuc PTRACE_SETSIGMASK is used
at "restore" time, doesn't this mean that TIF_RESTORE_SIGMASK/restore_sigmask
can not be set?

IOW, could you please explain how PTRACE_SETSIGMASK should be used, and why
it doesn't do something like

	if (test_tsk_restore_sigmask(child))
		child->saved_sigmask = new_set;
	else
		child->blocked = new_set;

which looks symmetrical to PTRACE_GETSIGMASK?

Oleg.