linux-kernel - Re: siginfo pid not populated from ptrace?

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Message-ID: <20181210153717.GA7581@redhat.com>
Date:   Mon, 10 Dec 2018 16:37:18 +0100
From:   Oleg Nesterov <oleg@...hat.com>
To:     "Eric W. Biederman" <ebiederm@...ssion.com>
Cc:     Tycho Andersen <tycho@...ho.ws>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Kees Cook <keescook@...omium.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Linux List Kernel Mailing <linux-kernel@...r.kernel.org>
Subject: Re: siginfo pid not populated from ptrace?

On 12/06, Eric W. Biederman wrote:
>
> The challenge is that we could be delivering this to a zombie signal
> group leader.

...

> Sigh it is probably time that I dig in and figure out how to avoid that
> case which we need to fix anyway because we can get the permission
> checks wrong for multi-threaded processes that call setuid and friends.

this is another issue... I am sure we have already discussed this, but I
failed to find any link to the previous discussion.

> Once that is sorted your small change will at least be safe.

I don't think so, any sub-thread can dequeue SIGSTOP unless type == PIDTYPE_PID,
this has nothing to do with the problems connected to zombie leader, or I
misunderstood you.

Oleg.