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From: Jann Horn <jannh@google.com>
To: Golden_Miller83@protonmail.ch
Cc: Steven Rostedt <rostedt@goodmis.org>,
	Nick Desaulniers <ndesaulniers@google.com>,
	Greg KH <greg@kroah.com>, Kees Cook <keescook@google.com>,
	salyzyn@android.com, kernel list <linux-kernel@vger.kernel.org>,
	Ingo Molnar <mingo@redhat.com>,
	kernel-team@android.com, stable@vger.kernel.org,
	Kernel Hardening <kernel-hardening@lists.openwall.com>
Subject: Re: [PATCH] tracing: do not leak kernel addresses
Date: Fri, 27 Jul 2018 15:40:32 +0200	[thread overview]
Message-ID: <CAG48ez1U=5nTOrnOqwMuXhdER-7XxJUYLcyYNuczwasQLQ0gXA@mail.gmail.com> (raw)
In-Reply-To: <753E9YR1QhdsPhsFoYuXCwfUzfyntDrc_A93hMUkktMi7lbh3KUZMcbfqKVWUfi15zYhuiDFant-ROa4QNV5shx74ff4hGngq2BOJDv-hq4=@protonmail.ch>

On Fri, Jul 27, 2018 at 2:07 PM Jordan Glover
<Golden_Miller83@protonmail.ch> wrote:
>
> On July 27, 2018 12:15 AM, Steven Rostedt <rostedt@goodmis.org> wrote:
>
> > On Thu, 26 Jul 2018 09:52:11 -0700
> > Nick Desaulniers ndesaulniers@google.com wrote:
> >
> > > See the section "Kernel addresses" in
> > > Documentation/security/self-protection. IIRC, the issue is that a
> > > process may have CAP_SYSLOG but not necessarily CAP_SYS_ADMIN (so it
> > > can read dmesg, but not necessarily issue a sysctl to change
> > > kptr_restrict), get compromised and used to leak kernel addresses,
> > > which can then be used to defeat KASLR.
> >
> > But the code doesn't go to dmesg. It's only available
> > via /sys/kernel/debug/tracing/printk_formats which is only available
> > via root. Nobody else has access to that directory.
> >
> > -- Steve
>
> I think the point was that when we take capabilities into account the root
> privileges aren't unequivocal anymore. The 'root' owned process with only
> 'CAP_SYSLOG' shouldn't have access to /sys/kernel/debug/tracing/printk_formats

Then they shouldn't have access to debugfs at all, right?

  reply	other threads:[~2018-07-27 13:41 UTC|newest]

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-07-25 20:22 [PATCH] tracing: do not leak kernel addresses Mark Salyzyn
2018-07-25 21:14 ` Nick Desaulniers
2018-07-26  1:07 ` Steven Rostedt
2018-07-26 15:14   ` Mark Salyzyn
2018-07-26 15:22     ` Steven Rostedt
2018-07-26 16:32       ` Nick Desaulniers
2018-07-26 16:37         ` Steven Rostedt
2018-07-26 16:59           ` Nick Desaulniers
2018-07-26 21:56             ` Nick Desaulniers
2018-07-26 15:31     ` Greg KH
2018-07-26 16:52       ` Nick Desaulniers
2018-07-26 22:15         ` Steven Rostedt
2018-07-27 12:07           ` Jordan Glover
2018-07-27 13:40             ` Jann Horn [this message]
2018-07-27 13:47               ` Steven Rostedt
2018-07-27 18:13                 ` Nick Desaulniers
2018-07-27 18:31                   ` Steven Rostedt
     [not found]                     ` <CAMx4XWv3OazvURuN1XU2+5C5tNDzPuTniMn_T=XTA4P8_uwS_A@mail.gmail.com>
2018-07-27 18:47                       ` Jann Horn
2018-07-27 18:58                         ` Jann Horn
2018-07-27 19:54                           ` Theodore Y. Ts'o
2018-07-27 20:11                             ` Steven Rostedt
2018-07-27 20:21                               ` Theodore Y. Ts'o
2018-07-27 20:53                                 ` Steven Rostedt
2018-07-27 22:05                                 ` Sandeep Patil
2018-07-28  0:04                                   ` Theodore Y. Ts'o
2018-07-30 14:35                                     ` Sandeep Patil

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