linux-kernel - Re: [PATCH v5] pidfd: add ioctl to retrieve pid info

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <20241007-endsieg-pigmente-357468af306b@brauner>
Date: Mon, 7 Oct 2024 14:11:59 +0200
From: Christian Brauner <brauner@...nel.org>
To: Luca Boccassi <luca.boccassi@...il.com>
Cc: Oleg Nesterov <oleg@...hat.com>, linux-kernel@...r.kernel.org, 
	christian@...uner.io
Subject: Re: [PATCH v5] pidfd: add ioctl to retrieve pid info

On Sun, Oct 06, 2024 at 10:33:08PM GMT, Luca Boccassi wrote:
> On Sun, 6 Oct 2024 at 19:56, Oleg Nesterov <oleg@...hat.com> wrote:
> >
> > On 10/06, Luca Boccassi wrote:
> > >
> > > I see, so what should I do here then? Check both? Or none?
> >
> > I don't know, because I don't know how are you going to use this API.
> >
> > > The caller
> > > needs to verify that the data is still valid at the point they use it
> > > anyway,
> >
> > So "none" should work fine? Just it should be documented that, say,
> > kinfo.pid can be 0 if we race with the exiting task.
> >
> > Just in case, you can also use lock_task_sighand() || return -ESRCH,
> > this way kinfo.*pid can't be zero. But I don't think this will buy too
> > much, the task can exit right after pidfd_info() returns.
> >
> > Oleg.
> 
> I think what we should do is check if any of those fields was set to
> 0, and return ESRCH in that case. This way either we return a full set
> of metadata that was correct at the time it was taken, or we provide
> nothing and a clear error. We cannot solve the race as you mentioned,
> but I think it is important to avoid providing incomplete information,
> so that either the data is complete or nothing is given back. If the
> information is complete but becomes stale later, that can happen and
> it's ok.

Agree.