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From: Masami Hiramatsu <mhiramat@kernel.org>
To: Matthew Garrett <mjg59@google.com>
Cc: James Morris <jmorris@namei.org>,
	LSM List <linux-security-module@vger.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	David Howells <dhowells@redhat.com>,
	Alexei Starovoitov <alexei.starovoitov@gmail.com>,
	"Naveen N . Rao" <naveen.n.rao@linux.ibm.com>,
	Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>,
	davem@davemloft.net
Subject: Re: [PATCH 22/27] Lock down kprobes
Date: Wed, 27 Mar 2019 07:47:55 +0900
Message-ID: <20190327074755.310fd73e613a7c0f8fa2d94d@kernel.org> (raw)
In-Reply-To: <CACdnJuss=NmcxS0UoTeopYzipt53ba5GTBwQ+YtJQXLj7_Q10w@mail.gmail.com>

On Tue, 26 Mar 2019 10:41:23 -0700
Matthew Garrett <mjg59@google.com> wrote:

> On Tue, Mar 26, 2019 at 5:30 AM Masami Hiramatsu <mhiramat@kernel.org> wrote:
> >
> > On Mon, 25 Mar 2019 15:09:49 -0700
> > Matthew Garrett <matthewgarrett@google.com> wrote:
> >
> > > From: David Howells <dhowells@redhat.com>
> > >
> > > Disallow the creation of kprobes when the kernel is locked down by
> > > preventing their registration.  This prevents kprobes from being used to
> > > access kernel memory, either to make modifications or to steal crypto data.
> >
> > Hmm, if you enforce signature check of modules, those modules
> > should be allowed to use kprobes?
> > I think we should introduce some kind of trust inheritance from
> > signed (trusted) modules.
> 
> Is there any way to install a kprobe /without/ it coming from a
> module? The presumption in lockdown mode is that module signing is
> enforced, so I'll admit to not being entirely clear on why this patch
> is needed in that case.

Yes, there are 2 paths, ftrace and perf(bpf). If you want to disable ftrace
path (which start from user's input via tracefs), this should be done in
trace_kprobe_create()@kernel/trace/trace_kprobe.c.
If you want to disable both, __register_trace_kprobe()@kernel/trace/trace_kprobe.c
is the best place.

Thank you,

-- 
Masami Hiramatsu <mhiramat@kernel.org>

  reply index

Thread overview: 50+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-03-25 22:09 [PULL REQUEST] Lockdown patches for 5.2 Matthew Garrett
2019-03-25 22:09 ` [PATCH 01/27] Add the ability to lock down access to the running kernel image Matthew Garrett
2019-03-26  5:30   ` Matthew Garrett
2019-03-25 22:09 ` [PATCH 02/27] Enforce module signatures if the kernel is locked down Matthew Garrett
2019-03-25 22:09 ` [PATCH 03/27] Restrict /dev/{mem,kmem,port} when " Matthew Garrett
2019-03-25 22:09 ` [PATCH 04/27] kexec_load: Disable at runtime if " Matthew Garrett
2019-03-25 22:09 ` [PATCH 05/27] Copy secure_boot flag in boot params across kexec reboot Matthew Garrett
2019-03-25 22:09 ` [PATCH 06/27] kexec_file: split KEXEC_VERIFY_SIG into KEXEC_SIG and KEXEC_SIG_FORCE Matthew Garrett
2019-03-25 22:09 ` [PATCH 07/27] kexec_file: Restrict at runtime if the kernel is locked down Matthew Garrett
2019-03-25 22:09 ` [PATCH 08/27] hibernate: Disable when " Matthew Garrett
2019-03-25 22:09 ` [PATCH 09/27] uswsusp: " Matthew Garrett
2019-03-25 22:09 ` [PATCH 10/27] PCI: Lock down BAR access " Matthew Garrett
2019-03-25 22:09 ` [PATCH 11/27] x86: Lock down IO port " Matthew Garrett
2019-03-25 22:09 ` [PATCH 12/27] x86/msr: Restrict MSR " Matthew Garrett
2019-03-25 23:40   ` Thomas Gleixner
2019-03-25 22:09 ` [PATCH 13/27] ACPI: Limit access to custom_method " Matthew Garrett
2019-03-25 22:09 ` [PATCH 14/27] acpi: Ignore acpi_rsdp kernel param when the kernel has been " Matthew Garrett
2019-03-25 22:09 ` [PATCH 15/27] acpi: Disable ACPI table override if the kernel is " Matthew Garrett
2019-03-25 22:09 ` [PATCH 16/27] acpi: Disable APEI error injection " Matthew Garrett
2019-03-25 22:09 ` [PATCH 17/27] Prohibit PCMCIA CIS storage when " Matthew Garrett
2019-03-25 22:09 ` [PATCH 18/27] Lock down TIOCSSERIAL Matthew Garrett
2019-03-25 22:09 ` [PATCH 19/27] Lock down module params that specify hardware parameters (eg. ioport) Matthew Garrett
2019-03-25 22:09 ` [PATCH 20/27] x86/mmiotrace: Lock down the testmmiotrace module Matthew Garrett
2019-03-25 23:35   ` Steven Rostedt
2019-03-25 22:09 ` [PATCH 21/27] Lock down /proc/kcore Matthew Garrett
2019-03-25 22:09 ` [PATCH 22/27] Lock down kprobes Matthew Garrett
2019-03-26 12:29   ` Masami Hiramatsu
2019-03-26 17:41     ` Matthew Garrett
2019-03-26 22:47       ` Masami Hiramatsu [this message]
2019-03-25 22:09 ` [PATCH 23/27] bpf: Restrict kernel image access functions when the kernel is locked down Matthew Garrett
2019-03-25 23:42   ` Stephen Hemminger
2019-03-25 23:59     ` Stephen Hemminger
2019-03-26  0:00     ` Daniel Borkmann
2019-03-26 13:54       ` Jordan Glover
2019-03-26  0:10     ` Andy Lutomirski
2019-03-26 18:57       ` James Morris
2019-03-26 19:22         ` Andy Lutomirski
2019-03-28  3:15           ` James Morris
2019-03-28 18:07             ` Matthew Garrett
2019-03-28 19:23               ` James Morris
2019-03-28 20:08                 ` Matthew Garrett
2019-03-26 20:19         ` Matthew Garrett
2019-03-25 22:09 ` [PATCH 24/27] Lock down perf Matthew Garrett
2019-03-25 22:09 ` [PATCH 25/27] debugfs: Restrict debugfs when the kernel is locked down Matthew Garrett
2019-03-26  0:31   ` Greg Kroah-Hartman
2019-03-26  0:38     ` Matthew Garrett
2019-03-26  0:43       ` Greg Kroah-Hartman
2019-03-25 22:09 ` [PATCH 26/27] lockdown: Print current->comm in restriction messages Matthew Garrett
2019-03-25 22:09 ` [PATCH 27/27] kexec: Allow kexec_file() with appropriate IMA policy when locked down Matthew Garrett
2019-03-26 15:33   ` Mimi Zohar

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