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From: Alexei Starovoitov <alexei.starovoitov@gmail.com>
To: David Howells <dhowells@redhat.com>
Cc: linux-security-module@vger.kernel.org,
	gnomes@lxorguk.ukuu.org.uk, linux-efi@vger.kernel.org,
	matthew.garrett@nebula.com, gregkh@linuxfoundation.org,
	linux-kernel@vger.kernel.org, jforbes@redhat.com,
	Daniel Borkmann <daniel@iogearbox.net>,
	"David S. Miller" <davem@davemloft.net>,
	netdev@vger.kernel.org
Subject: Re: [PATCH 18/27] bpf: Restrict kernel image access functions when the kernel is locked down
Date: Thu, 19 Oct 2017 15:18:30 -0700
Message-ID: <20171019221829.7m5nczg3ltqmhzom@ast-mbp> (raw)
In-Reply-To: <150842476953.7923.18174368926573855810.stgit@warthog.procyon.org.uk>

On Thu, Oct 19, 2017 at 03:52:49PM +0100, David Howells wrote:
> From: Chun-Yi Lee <jlee@suse.com>
> 
> There are some bpf functions can be used to read kernel memory:
> bpf_probe_read, bpf_probe_write_user and bpf_trace_printk.  These allow
> private keys in kernel memory (e.g. the hibernation image signing key) to
> be read by an eBPF program.  Prohibit those functions when the kernel is
> locked down.
> 
> Signed-off-by: Chun-Yi Lee <jlee@suse.com>
> Signed-off-by: David Howells <dhowells@redhat.com>
> cc: netdev@vger.kernel.org
> ---
> 
>  kernel/trace/bpf_trace.c |   11 +++++++++++
>  1 file changed, 11 insertions(+)
> 
> diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
> index dc498b605d5d..35e85a3fdb37 100644
> --- a/kernel/trace/bpf_trace.c
> +++ b/kernel/trace/bpf_trace.c
> @@ -65,6 +65,11 @@ BPF_CALL_3(bpf_probe_read, void *, dst, u32, size, const void *, unsafe_ptr)
>  {
>  	int ret;
>  
> +	if (kernel_is_locked_down("BPF")) {
> +		memset(dst, 0, size);
> +		return -EPERM;
> +	}

That doesn't help the lockdown purpose.
If you don't trust the root the only way to prevent bpf read
memory is to disable the whole thing.
Have a single check in sys_bpf() to disallow everything if kernel_is_locked_down()
and don't add overhead to critical path like bpf_probe_read().

  reply index

Thread overview: 151+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-10-19 14:50 [PATCH 00/27] security, efi: Add kernel lockdown David Howells
2017-10-19 14:50 ` [PATCH 01/27] Add the ability to lock down access to the running kernel image David Howells
2017-10-20 23:19   ` James Morris
2017-10-19 14:50 ` [PATCH 02/27] Add a SysRq option to lift kernel lockdown David Howells
2017-10-19 17:20   ` Randy Dunlap
2017-10-19 22:12   ` David Howells
2017-11-07 17:39   ` Thiago Jung Bauermann
2017-11-07 22:56   ` David Howells
2017-10-19 14:50 ` [PATCH 03/27] Enforce module signatures if the kernel is locked down David Howells
2017-10-20  6:33   ` joeyli
2017-10-20 23:21   ` James Morris
2017-10-27 18:48   ` Mimi Zohar
2017-10-30 17:00   ` David Howells
2017-10-30 17:52     ` Mimi Zohar
2017-11-02 17:22   ` David Howells
2017-11-02 19:13     ` Mimi Zohar
2017-11-02 21:30     ` David Howells
2017-11-02 21:41       ` Mimi Zohar
2017-11-02 22:01       ` David Howells
2017-11-02 22:18         ` Mimi Zohar
2017-10-19 14:51 ` [PATCH 04/27] Restrict /dev/mem and /dev/kmem when " David Howells
2017-10-20  6:37   ` joeyli
2017-10-20 23:21   ` James Morris
2017-10-19 14:51 ` [PATCH 05/27] kexec: Disable at runtime if " David Howells
2017-10-20  6:38   ` joeyli
2017-10-20 23:22   ` James Morris
2017-10-19 14:51 ` [PATCH 06/27] Copy secure_boot flag in boot params across kexec reboot David Howells
2017-10-20  6:40   ` joeyli
2017-10-19 14:51 ` [PATCH 07/27] kexec_file: Disable at runtime if securelevel has been set David Howells
2017-10-20 23:26   ` James Morris
2017-10-23 15:54   ` Mimi Zohar
2017-10-26  7:42     ` joeyli
2017-10-26 14:17       ` Mimi Zohar
2017-10-27 19:30         ` Mimi Zohar
2017-10-27 19:32         ` Mimi Zohar
2017-10-28  8:34           ` joeyli
2017-10-29 22:26             ` Mimi Zohar
2017-10-30  9:00       ` David Howells
2017-10-30 12:01         ` Mimi Zohar
2017-10-26 15:02     ` David Howells
2017-10-26 15:46       ` Mimi Zohar
2017-10-30 15:49       ` David Howells
2017-10-30 16:43         ` Mimi Zohar
2017-11-02 17:00         ` David Howells
2017-10-26 14:51   ` David Howells
2017-11-02 17:29   ` David Howells
2017-10-19 14:51 ` [PATCH 08/27] hibernate: Disable when the kernel is locked down David Howells
2017-10-20  6:40   ` joeyli
2017-10-19 14:51 ` [PATCH 09/27] uswsusp: " David Howells
2017-10-20  6:41   ` joeyli
2017-10-20 23:29   ` James Morris
2017-10-19 14:51 ` [PATCH 10/27] PCI: Lock down BAR access " David Howells
2017-10-20  6:42   ` joeyli
2017-10-19 14:51 ` [PATCH 11/27] x86: Lock down IO port " David Howells
2017-10-20  6:43   ` joeyli
2017-10-19 14:52 ` [PATCH 12/27] x86/msr: Restrict MSR " David Howells
2017-10-20  6:43   ` joeyli
2017-10-20 18:09   ` Alan Cox
2017-10-20 20:48   ` David Howells
2017-10-21  4:39     ` joeyli
2017-10-23 14:49   ` David Howells
2017-10-25 14:03     ` joeyli
2017-10-19 14:52 ` [PATCH 13/27] asus-wmi: Restrict debugfs interface " David Howells
2017-10-20  6:44   ` joeyli
2017-10-19 14:52 ` [PATCH 14/27] ACPI: Limit access to custom_method " David Howells
2017-10-20  6:45   ` joeyli
2017-10-19 14:52 ` [PATCH 15/27] acpi: Ignore acpi_rsdp kernel param when the kernel has been " David Howells
2017-10-20  6:45   ` joeyli
2017-10-19 14:52 ` [PATCH 16/27] acpi: Disable ACPI table override if the kernel is " David Howells
2017-10-20  6:46   ` joeyli
2017-10-19 14:52 ` [PATCH 17/27] acpi: Disable APEI error injection " David Howells
2017-10-20  6:47   ` joeyli
2017-10-19 14:52 ` [PATCH 18/27] bpf: Restrict kernel image access functions when " David Howells
2017-10-19 22:18   ` Alexei Starovoitov [this message]
2017-10-20  2:47     ` joeyli
2017-10-20  8:08     ` David Howells
2017-10-20 15:57       ` jlee
2017-10-20 23:00         ` Alexei Starovoitov
2017-10-23 14:51         ` David Howells
2017-10-20 16:03       ` David Howells
2017-10-20 16:43         ` jlee
2017-10-23 14:53         ` David Howells
2017-10-25  7:07           ` joeyli
2017-10-19 22:48   ` David Howells
2017-10-19 23:31     ` Alexei Starovoitov
2017-11-09 17:15     ` David Howells
2017-10-19 14:52 ` [PATCH 19/27] scsi: Lock down the eata driver David Howells
2017-10-19 14:53 ` [PATCH 20/27] Prohibit PCMCIA CIS storage when the kernel is locked down David Howells
2017-10-19 14:53 ` [PATCH 21/27] Lock down TIOCSSERIAL David Howells
2017-10-19 14:53 ` [PATCH 22/27] Lock down module params that specify hardware parameters (eg. ioport) David Howells
2017-10-19 14:53 ` [PATCH 23/27] x86/mmiotrace: Lock down the testmmiotrace module David Howells
2017-10-19 14:53 ` [PATCH 24/27] debugfs: Disallow use of debugfs files when the kernel is locked down David Howells
2017-10-19 14:53 ` [PATCH 25/27] Lock down /proc/kcore David Howells
2017-10-21  2:11   ` James Morris
2017-10-23 14:56   ` David Howells
2017-10-19 14:53 ` [PATCH 26/27] efi: Add an EFI_SECURE_BOOT flag to indicate secure boot mode David Howells
2017-10-21  2:19   ` James Morris
2017-10-23 14:58   ` David Howells
2017-10-19 14:53 ` [PATCH 27/27] efi: Lock down the kernel if booted in " David Howells
2017-10-19 22:39 ` [PATCH 00/27] security, efi: Add kernel lockdown David Howells
2017-10-23 14:34 ` [PATCH 04/27] Restrict /dev/mem and /dev/kmem when the kernel is locked down David Howells
2017-10-24 10:48   ` Ethan Zhao
2017-10-24 14:56   ` David Howells
2017-11-02 22:01 ` [PATCH 00/27] security, efi: Add kernel lockdown Mimi Zohar
2017-11-02 22:04 ` Firmware signing -- " David Howells
2017-11-02 22:10   ` Mimi Zohar
2017-11-07 23:07     ` Luis R. Rodriguez
2017-11-08  6:15       ` AKASHI, Takahiro
2017-11-08 19:46         ` Luis R. Rodriguez
2017-11-09  1:48           ` AKASHI, Takahiro
2017-11-09  2:17             ` Mimi Zohar
2017-11-09  4:46               ` AKASHI, Takahiro
2017-11-10 13:37                 ` Mimi Zohar
2017-11-11  2:32                 ` Alan Cox
2017-11-13 11:49                   ` Mimi Zohar
2017-11-13 17:42                   ` Luis R. Rodriguez
2017-11-13 21:08                     ` Alan Cox
2017-12-04 19:51                       ` Luis R. Rodriguez
2017-12-07 15:32                         ` Alan Cox
2017-11-13 21:44                     ` David Howells
2017-11-13 22:09                       ` Linus Torvalds
2017-11-14  0:20                         ` Alan Cox
2017-11-14 12:21                         ` Mimi Zohar
2017-11-14 12:38                           ` Greg Kroah-Hartman
2017-11-14 13:17                             ` Mimi Zohar
2017-11-14 17:34                           ` Linus Torvalds
2017-11-14 19:58                             ` Matthew Garrett
2017-11-14 20:18                               ` Linus Torvalds
2017-11-14 20:31                                 ` Matthew Garrett
2017-11-14 20:35                                   ` Linus Torvalds
2017-11-14 20:37                                     ` Matthew Garrett
2017-11-14 20:50                                 ` Luis R. Rodriguez
2017-11-14 20:55                                   ` Matthew Garrett
2017-11-14 22:14                                     ` James Bottomley
2017-11-14 22:17                                       ` Matthew Garrett
2017-11-14 22:31                                         ` James Bottomley
2017-11-14 22:34                                           ` Matthew Garrett
2017-11-15 11:49                                   ` Mimi Zohar
2017-11-15 17:52                                     ` Luis R. Rodriguez
2017-11-15 19:56                                       ` Mimi Zohar
2017-11-15 20:46                                         ` Luis R. Rodriguez
2017-11-16  0:05                                           ` Mimi Zohar
2017-12-05 10:27                                 ` Pavel Machek
2017-12-07 23:02                                   ` Luis R. Rodriguez
2017-12-08 17:11                                     ` Alan Cox
2017-11-10  1:46             ` Luis R. Rodriguez
2017-11-10 13:45               ` Mimi Zohar
2017-11-13 18:50                 ` Luis R. Rodriguez
2017-11-13 19:08                   ` Luis R. Rodriguez
2017-11-08 20:01       ` Mimi Zohar
2017-11-08 20:09         ` Luis R. Rodriguez

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