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From: Matthew Garrett <matthewgarrett@google.com>
To: jmorris@namei.org
Cc: linux-security-module@vger.kernel.org,
	linux-kernel@vger.kernel.org, dhowells@redhat.com,
	linux-api@vger.kernel.org, luto@kernel.org,
	Matthew Garrett <mjg59@srcf.ucam.org>,
	Matthew Garrett <mjg59@google.com>,
	x86@kernel.org
Subject: [PATCH V31 03/25] Restrict /dev/{mem,kmem,port} when the kernel is locked down
Date: Tue, 26 Mar 2019 11:27:19 -0700	[thread overview]
Message-ID: <20190326182742.16950-4-matthewgarrett@google.com> (raw)
In-Reply-To: <20190326182742.16950-1-matthewgarrett@google.com>

From: Matthew Garrett <mjg59@srcf.ucam.org>

Allowing users to read and write to core kernel memory makes it possible
for the kernel to be subverted, avoiding module loading restrictions, and
also to steal cryptographic information.

Disallow /dev/mem and /dev/kmem from being opened this when the kernel has
been locked down to prevent this.

Also disallow /dev/port from being opened to prevent raw ioport access and
thus DMA from being used to accomplish the same thing.

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Matthew Garrett <mjg59@google.com>
Cc: x86@kernel.org
---
 drivers/char/mem.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/char/mem.c b/drivers/char/mem.c
index b08dc50f9f26..67b85939b1bd 100644
--- a/drivers/char/mem.c
+++ b/drivers/char/mem.c
@@ -786,6 +786,8 @@ static loff_t memory_lseek(struct file *file, loff_t offset, int orig)
 
 static int open_port(struct inode *inode, struct file *filp)
 {
+	if (kernel_is_locked_down("/dev/mem,kmem,port", LOCKDOWN_INTEGRITY))
+		return -EPERM;
 	return capable(CAP_SYS_RAWIO) ? 0 : -EPERM;
 }
 
-- 
2.21.0.392.gf8f6787159e-goog


  parent reply	other threads:[~2019-03-26 18:28 UTC|newest]

Thread overview: 58+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-03-26 18:27 [PATCH V31 00/25] Add support for kernel lockdown Matthew Garrett
2019-03-26 18:27 ` [PATCH V31 01/25] Add the ability to lock down access to the running kernel image Matthew Garrett
2019-03-26 18:27 ` [PATCH V31 02/25] Enforce module signatures if the kernel is locked down Matthew Garrett
2019-03-26 18:27 ` Matthew Garrett [this message]
2019-03-26 18:27 ` [PATCH V31 04/25] kexec_load: Disable at runtime " Matthew Garrett
2019-03-26 18:27 ` [PATCH V31 05/25] Copy secure_boot flag in boot params across kexec reboot Matthew Garrett
2019-03-26 18:27 ` [PATCH V31 06/25] kexec_file: split KEXEC_VERIFY_SIG into KEXEC_SIG and KEXEC_SIG_FORCE Matthew Garrett
2019-06-21  6:34   ` Dave Young
2019-06-21 20:13     ` Matthew Garrett
2019-06-21 20:14       ` Matthew Garrett
2019-03-26 18:27 ` [PATCH V31 07/25] kexec_file: Restrict at runtime if the kernel is locked down Matthew Garrett
2019-06-21  6:43   ` Dave Young
2019-06-21 20:18     ` Matthew Garrett
2019-06-24  1:52       ` Dave Young
2019-06-24 21:06         ` Matthew Garrett
2019-06-24 21:27           ` Mimi Zohar
2019-06-25  0:02             ` Matthew Garrett
2019-06-25  1:46               ` Mimi Zohar
2019-06-25  2:51           ` Dave Young
2019-03-26 18:27 ` [PATCH V31 08/25] hibernate: Disable when " Matthew Garrett
2019-03-26 18:27 ` [PATCH V31 09/25] uswsusp: " Matthew Garrett
2019-03-26 18:27 ` [PATCH V31 10/25] PCI: Lock down BAR access " Matthew Garrett
2019-03-26 20:55   ` Andy Lutomirski
2019-03-26 21:19     ` Alex Williamson
2019-03-26 18:27 ` [PATCH V31 11/25] x86: Lock down IO port " Matthew Garrett
2019-03-26 20:56   ` Andy Lutomirski
2019-03-26 18:27 ` [PATCH V31 12/25] x86/msr: Restrict MSR " Matthew Garrett
2019-03-26 18:27 ` [PATCH V31 13/25] ACPI: Limit access to custom_method " Matthew Garrett
2019-03-26 18:27 ` [PATCH V31 14/25] acpi: Ignore acpi_rsdp kernel param when the kernel has been " Matthew Garrett
2019-03-26 18:27 ` [PATCH V31 15/25] acpi: Disable ACPI table override if the kernel is " Matthew Garrett
2019-03-26 18:27 ` [PATCH V31 16/25] Prohibit PCMCIA CIS storage when " Matthew Garrett
2019-03-26 18:27 ` [PATCH V31 17/25] Lock down TIOCSSERIAL Matthew Garrett
2019-03-26 18:27 ` [PATCH V31 18/25] Lock down module params that specify hardware parameters (eg. ioport) Matthew Garrett
2019-03-26 18:27 ` [PATCH V31 19/25] x86/mmiotrace: Lock down the testmmiotrace module Matthew Garrett
2019-03-27 15:57   ` Steven Rostedt
2019-03-27 16:55     ` Matthew Garrett
2019-03-26 18:27 ` [PATCH V31 20/25] Lock down /proc/kcore Matthew Garrett
2019-03-26 18:27 ` [PATCH V31 21/25] Lock down kprobes when in confidentiality mode Matthew Garrett
2019-03-26 18:27 ` [PATCH V31 22/25] bpf: Restrict bpf when kernel lockdown is " Matthew Garrett
2019-03-26 19:21   ` Andy Lutomirski
2019-03-26 18:27 ` [PATCH V31 23/25] Lock down perf when " Matthew Garrett
2019-03-26 18:27 ` [PATCH V31 24/25] lockdown: Print current->comm in restriction messages Matthew Garrett
2019-03-26 18:27 ` [PATCH V31 25/25] debugfs: Disable open() when kernel is locked down Matthew Garrett
2019-03-26 19:20   ` Andy Lutomirski
2019-03-26 19:21     ` Matthew Garrett
2019-03-27  0:30     ` Greg KH
2019-03-27  4:29       ` Andy Lutomirski
2019-03-27  5:06         ` Greg KH
2019-03-27  5:29           ` Andy Lutomirski
2019-03-27  5:33             ` Greg KH
2019-03-27 16:53               ` James Morris
2019-03-27 17:39               ` Andy Lutomirski
2019-03-27 17:42                 ` Matthew Garrett
2019-03-27 18:29                   ` Greg KH
2019-03-27 18:31                 ` Greg KH
2019-03-27  0:31   ` Greg KH
2019-03-27  2:06     ` Matthew Garrett
2019-03-27  2:35       ` Greg KH

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