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

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Message-ID: <20181210154442.GA19268@cisco>
Date:   Mon, 10 Dec 2018 08:44:42 -0700
From:   Tycho Andersen <tycho@...ho.ws>
To:     Oleg Nesterov <oleg@...hat.com>
Cc:     "Eric W. Biederman" <ebiederm@...ssion.com>,
        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?

Hi Oleg,

On Mon, Dec 10, 2018 at 04:37:18PM +0100, Oleg Nesterov wrote:
> 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.

I think the conclusion about this bug is that we're just not going to
fix it, Kees sent a patch to remove the check from the test:

https://lore.kernel.org/lkml/20181206235038.GA18273@beast/T/#u

So I will drop my patch.

Cheers,

Tycho