From: Suren Baghdasaryan <surenb@google.com>
To: Oleg Nesterov <oleg@redhat.com>
Cc: "Michal Hocko" <mhocko@suse.com>,
"Andrew Morton" <akpm@linux-foundation.org>,
"Jann Horn" <jannh@google.com>,
"Kees Cook" <keescook@chromium.org>,
"Jeffrey Vander Stoep" <jeffv@google.com>,
"Minchan Kim" <minchan@kernel.org>,
"Shakeel Butt" <shakeelb@google.com>,
"David Rientjes" <rientjes@google.com>,
"Edgar Arriaga García" <edgararriaga@google.com>,
"Tim Murray" <timmurray@google.com>,
linux-mm <linux-mm@kvack.org>,
selinux@vger.kernel.org, "Linux API" <linux-api@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
kernel-team <kernel-team@android.com>
Subject: Re: [PATCH v2 1/1] mm/madvise: replace ptrace attach requirement for process_madvise
Date: Tue, 12 Jan 2021 09:51:24 -0800 [thread overview]
Message-ID: <CAJuCfpFQz=x-LvONO3c4iqjKP4NKJMgUuiYc8HACKHAv1Omu0w@mail.gmail.com> (raw)
In-Reply-To: <20210112174507.GA23780@redhat.com>
On Tue, Jan 12, 2021 at 9:45 AM Oleg Nesterov <oleg@redhat.com> wrote:
>
> On 01/12, Michal Hocko wrote:
> >
> > On Mon 11-01-21 09:06:22, Suren Baghdasaryan wrote:
> >
> > > What we want is the ability for one process to influence another process
> > > in order to optimize performance across the entire system while leaving
> > > the security boundary intact.
> > > Replace PTRACE_MODE_ATTACH with a combination of PTRACE_MODE_READ
> > > and CAP_SYS_NICE. PTRACE_MODE_READ to prevent leaking ASLR metadata
> > > and CAP_SYS_NICE for influencing process performance.
> >
> > I have to say that ptrace modes are rather obscure to me. So I cannot
> > really judge whether MODE_READ is sufficient. My understanding has
> > always been that this is requred to RO access to the address space. But
> > this operation clearly has a visible side effect. Do we have any actual
> > documentation for the existing modes?
> >
> > I would be really curious to hear from Jann and Oleg (now Cced).
>
> Can't comment, sorry. I never understood these security checks and never tried.
> IIUC only selinux/etc can treat ATTACH/READ differently and I have no idea what
> is the difference.
I haven't seen a written explanation on ptrace modes but when I
consulted Jann his explanation was:
PTRACE_MODE_READ means you can inspect metadata about processes with
the specified domain, across UID boundaries.
PTRACE_MODE_ATTACH means you can fully impersonate processes with the
specified domain, across UID boundaries.
He did agree that in this case PTRACE_MODE_ATTACH seems too
restrictive (we do not try to gain full control or impersonate a
process) and PTRACE_MODE_READ is a better choice.
>
> Oleg.
>
next prev parent reply other threads:[~2021-01-12 17:51 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-11 17:06 [PATCH v2 1/1] mm/madvise: replace ptrace attach requirement for process_madvise Suren Baghdasaryan
2021-01-11 18:33 ` Kees Cook
2021-01-12 1:22 ` Andrew Morton
2021-01-12 17:36 ` Suren Baghdasaryan
2021-01-12 7:46 ` Michal Hocko
2021-01-12 17:45 ` Oleg Nesterov
2021-01-12 17:51 ` Suren Baghdasaryan [this message]
2021-01-13 14:22 ` Michal Hocko
2021-01-13 18:08 ` Suren Baghdasaryan
2021-01-20 13:17 ` Jann Horn
2021-01-20 16:57 ` Suren Baghdasaryan
2021-01-20 20:46 ` Suren Baghdasaryan
2021-01-26 13:52 ` Michal Hocko
2021-01-28 19:51 ` Suren Baghdasaryan
2021-01-29 7:08 ` Suren Baghdasaryan
2021-02-02 5:34 ` Suren Baghdasaryan
[not found] ` <CAJuCfpEOE8=L1fT4FSauy65cS82M_kW3EzTgH89ewE9HudL=VA@mail.gmail.com>
2021-03-03 0:17 ` Andrew Morton
2021-03-03 0:19 ` Suren Baghdasaryan
2021-03-03 19:00 ` Suren Baghdasaryan
2021-01-12 18:12 ` Suren Baghdasaryan
2021-01-13 14:19 ` Michal Hocko
2021-01-20 5:01 ` James Morris
2021-01-20 16:49 ` Suren Baghdasaryan
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