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From: Matthew Garrett <mjg59@google.com>
To: Daniel Borkmann <daniel@iogearbox.net>
Cc: James Morris <jmorris@namei.org>,
	LSM List <linux-security-module@vger.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Linux API <linux-api@vger.kernel.org>,
	David Howells <dhowells@redhat.com>,
	Alexei Starovoitov <alexei.starovoitov@gmail.com>,
	Network Development <netdev@vger.kernel.org>,
	Chun-Yi Lee <jlee@suse.com>, Jann Horn <jannh@google.com>,
	bpf@vger.kernel.org
Subject: Re: [PATCH V34 23/29] bpf: Restrict bpf when kernel lockdown is in confidentiality mode
Date: Mon, 24 Jun 2019 12:54:00 -0700	[thread overview]
Message-ID: <CACdnJuvR2bn3y3fYzg06GWXXgAGjgED2Dfa5g0oAwJ28qCCqBg@mail.gmail.com> (raw)
In-Reply-To: <739e21b5-9559-d588-3542-bf0bc81de1b2@iogearbox.net>

On Mon, Jun 24, 2019 at 8:37 AM Daniel Borkmann <daniel@iogearbox.net> wrote:
>
> On 06/22/2019 02:03 AM, Matthew Garrett wrote:
> > From: David Howells <dhowells@redhat.com>
> >
> > There are some bpf functions can be used to read kernel memory:
>
> Nit: that

Fixed.

> > bpf_probe_read, bpf_probe_write_user and bpf_trace_printk.  These allow
>
> Please explain how bpf_probe_write_user reads kernel memory ... ?!

Ha.

> > private keys in kernel memory (e.g. the hibernation image signing key) to
> > be read by an eBPF program and kernel memory to be altered without
>
> ... and while we're at it, also how they allow "kernel memory to be
> altered without restriction". I've been pointing this false statement
> out long ago.

Yup. How's the following description:

    bpf: Restrict bpf when kernel lockdown is in confidentiality mode

    There are some bpf functions that can be used to read kernel memory and
    exfiltrate it to userland: bpf_probe_read, bpf_probe_write_user and
    bpf_trace_printk.  These could be abused to (eg) allow private
keys in kernel
    memory to be leaked. Disable them if the kernel has been locked
down in confidentiality
    mode.

> This whole thing is still buggy as has been pointed out before by
> Jann. For helpers like above and few others below, error conditions
> must clear the buffer ...

Sorry, yes. My fault.

  reply	other threads:[~2019-06-24 19:54 UTC|newest]

Thread overview: 97+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-06-22  0:03 [PATCH V34 00/29] Lockdown as an LSM Matthew Garrett
2019-06-22  0:03 ` [PATCH V34 01/29] security: Support early LSMs Matthew Garrett
2019-06-22 23:36   ` Kees Cook
2019-06-22  0:03 ` [PATCH V34 02/29] security: Add a "locked down" LSM hook Matthew Garrett
2019-06-22 23:37   ` Kees Cook
2019-06-22  0:03 ` [PATCH V34 03/29] security: Add a static lockdown policy LSM Matthew Garrett
2019-06-22 23:37   ` Kees Cook
2019-06-22  0:03 ` [PATCH V34 04/29] Enforce module signatures if the kernel is locked down Matthew Garrett
2019-06-22 23:48   ` Kees Cook
2019-06-22  0:03 ` [PATCH V34 05/29] Restrict /dev/{mem,kmem,port} when " Matthew Garrett
2019-06-22 23:52   ` Kees Cook
2019-06-22  0:03 ` [PATCH V34 06/29] kexec_load: Disable at runtime if " Matthew Garrett
2019-06-22  0:03   ` Matthew Garrett
2019-06-22 23:52   ` Kees Cook
2019-06-22 23:52     ` Kees Cook
2019-06-22  0:03 ` [PATCH V34 07/29] Copy secure_boot flag in boot params across kexec reboot Matthew Garrett
2019-06-22  0:03   ` Matthew Garrett
2019-06-22 23:53   ` Kees Cook
2019-06-22 23:53     ` Kees Cook
2019-06-22  0:03 ` [PATCH V34 08/29] kexec_file: split KEXEC_VERIFY_SIG into KEXEC_SIG and KEXEC_SIG_FORCE Matthew Garrett
2019-06-22  0:03   ` Matthew Garrett
2019-06-24  2:01   ` Dave Young
2019-06-24  2:01     ` Dave Young
2019-06-25  2:35     ` Dave Young
2019-06-25  2:35       ` Dave Young
2019-06-22  0:03 ` [PATCH V34 09/29] kexec_file: Restrict at runtime if the kernel is locked down Matthew Garrett
2019-06-22  0:03   ` Matthew Garrett
2019-06-22  0:03   ` Matthew Garrett
2019-06-22 23:54   ` Kees Cook
2019-06-22 23:54     ` Kees Cook
2019-06-27  4:59   ` James Morris
2019-06-27  4:59     ` James Morris
2019-06-27 15:28     ` Matthew Garrett
2019-06-27 15:28       ` Matthew Garrett
2019-06-27 18:14       ` James Morris
2019-06-27 18:14         ` James Morris
2019-06-27 18:14         ` James Morris
2019-06-27 23:17         ` Matthew Garrett
2019-06-27 23:17           ` Matthew Garrett
2019-06-22  0:03 ` [PATCH V34 10/29] hibernate: Disable when " Matthew Garrett
2019-06-22 17:52   ` Pavel Machek
2019-06-24 13:21     ` Jiri Kosina
2019-07-10 15:26       ` Joey Lee
2019-07-10 15:26         ` Joey Lee
2019-07-11  4:11       ` joeyli
2019-06-22 23:55   ` Kees Cook
2019-06-22  0:03 ` [PATCH V34 11/29] PCI: Lock down BAR access " Matthew Garrett
2019-06-22 23:55   ` Kees Cook
2019-06-22  0:03 ` [PATCH V34 12/29] x86: Lock down IO port " Matthew Garrett
2019-06-22 23:58   ` Kees Cook
2019-06-22  0:03 ` [PATCH V34 13/29] x86/msr: Restrict MSR " Matthew Garrett
2019-06-22  0:03 ` [PATCH V34 14/29] ACPI: Limit access to custom_method " Matthew Garrett
2019-06-22 23:59   ` Kees Cook
2019-06-22  0:03 ` [PATCH V34 15/29] acpi: Ignore acpi_rsdp kernel param when the kernel has been " Matthew Garrett
2019-06-22 23:59   ` Kees Cook
2019-06-22  0:03 ` [PATCH V34 16/29] acpi: Disable ACPI table override if the kernel is " Matthew Garrett
2019-06-22  0:03   ` Matthew Garrett
2019-06-23  0:00   ` Kees Cook
2019-06-22  0:03 ` [PATCH V34 17/29] Prohibit PCMCIA CIS storage when " Matthew Garrett
2019-06-23  0:00   ` Kees Cook
2019-06-22  0:03 ` [PATCH V34 18/29] Lock down TIOCSSERIAL Matthew Garrett
2019-06-23  0:01   ` Kees Cook
2019-06-22  0:03 ` [PATCH V34 19/29] Lock down module params that specify hardware parameters (eg. ioport) Matthew Garrett
2019-06-23  0:04   ` Kees Cook
2019-06-27  1:49   ` Daniel Axtens
2019-06-27 15:30     ` Matthew Garrett
2019-06-22  0:03 ` [PATCH V34 20/29] x86/mmiotrace: Lock down the testmmiotrace module Matthew Garrett
2019-06-23  0:04   ` Kees Cook
2019-06-23 11:08   ` Thomas Gleixner
2019-06-22  0:03 ` [PATCH V34 21/29] Lock down /proc/kcore Matthew Garrett
2019-06-23  0:05   ` Kees Cook
2019-06-22  0:03 ` [PATCH V34 22/29] Lock down tracing and perf kprobes when in confidentiality mode Matthew Garrett
2019-06-23  0:09   ` Kees Cook
2019-06-23  1:57   ` Masami Hiramatsu
2019-06-22  0:03 ` [PATCH V34 23/29] bpf: Restrict bpf when kernel lockdown is " Matthew Garrett
2019-06-23  0:09   ` Kees Cook
2019-06-24 15:15   ` Daniel Borkmann
2019-06-24 19:54     ` Matthew Garrett [this message]
2019-06-24 20:08       ` Andy Lutomirski
2019-06-24 20:15         ` Matthew Garrett
2019-06-24 20:59         ` Daniel Borkmann
2019-06-24 21:30           ` Matthew Garrett
2019-06-22  0:03 ` [PATCH V34 24/29] Lock down perf when " Matthew Garrett
2019-06-23  0:12   ` Kees Cook
2019-06-22  0:03 ` [PATCH V34 25/29] kexec: Allow kexec_file() with appropriate IMA policy when locked down Matthew Garrett
2019-06-22  0:03 ` [PATCH V34 26/29] debugfs: Restrict debugfs when the kernel is " Matthew Garrett
2019-06-22  0:03 ` [PATCH V34 27/29] tracefs: Restrict tracefs " Matthew Garrett
2019-06-22  0:03 ` [PATCH V34 28/29] efi: Restrict efivar_ssdt_load " Matthew Garrett
2019-06-23  0:14   ` Kees Cook
2019-06-25 15:00   ` Ard Biesheuvel
2019-06-22  0:03 ` [PATCH V34 29/29] lockdown: Print current->comm in restriction messages Matthew Garrett
2019-06-23  0:25   ` Kees Cook
2019-06-24 23:01 ` [PATCH V34 00/29] Lockdown as an LSM James Morris
2019-06-24 23:47   ` Casey Schaufler
2019-06-24 23:56   ` Matthew Garrett
2019-06-25  6:04     ` James Morris
2019-06-25  8:16   ` John Johansen

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