[V38,18/29] Lock down TIOCSSERIAL

Message ID	20190808000721.124691-19-matthewgarrett@google.com (mailing list archive)
State	New, archived
Headers	show Return-Path: <linux-security-module-owner@kernel.org> Date: Wed, 7 Aug 2019 17:07:10 -0700 In-Reply-To: <20190808000721.124691-1-matthewgarrett@google.com> Message-Id: <20190808000721.124691-19-matthewgarrett@google.com> Mime-Version: 1.0 References: <20190808000721.124691-1-matthewgarrett@google.com> Subject: [PATCH V38 18/29] Lock down TIOCSSERIAL From: Matthew Garrett <matthewgarrett@google.com> To: jmorris@namei.org Cc: linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org, linux-api@vger.kernel.org, David Howells <dhowells@redhat.com>, Greg Kroah-Hartman <gregkh@linuxfoundation.org>, Matthew Garrett <mjg59@google.com>, Kees Cook <keescook@chromium.org>, Jiri Slaby <jslaby@suse.com>, linux-serial@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Sender: owner-linux-security-module@vger.kernel.org Precedence: bulk
Series	security: Add support for locking down the kernel \| expand [V38,00/29] security: Add support for locking down the kernel [V38,01/29] security: Support early LSMs [V38,02/29] security: Add a "locked down" LSM hook [V38,03/29] security: Add a static lockdown policy LSM [V38,04/29] Enforce module signatures if the kernel is locked down [V38,05/29] Restrict /dev/{mem,kmem,port} when the kernel is locked down [V38,06/29] kexec_load: Disable at runtime if the kernel is locked down [V38,07/29] Copy secure_boot flag in boot params across kexec reboot [V38,08/29] kexec_file: split KEXEC_VERIFY_SIG into KEXEC_SIG and KEXEC_SIG_FORCE [V38,09/29] kexec_file: Restrict at runtime if the kernel is locked down [V38,10/29] hibernate: Disable when the kernel is locked down [V38,11/29] PCI: Lock down BAR access when the kernel is locked down [V38,12/29] x86: Lock down IO port access when the kernel is locked down [V38,13/29] x86/msr: Restrict MSR access when the kernel is locked down [V38,14/29] ACPI: Limit access to custom_method when the kernel is locked down [V38,15/29] acpi: Ignore acpi_rsdp kernel param when the kernel has been locked down [V38,16/29] acpi: Disable ACPI table override if the kernel is locked down [V38,17/29] Prohibit PCMCIA CIS storage when the kernel is locked down [V38,18/29] Lock down TIOCSSERIAL [V38,19/29] Lock down module params that specify hardware parameters (eg. ioport) [V38,20/29] x86/mmiotrace: Lock down the testmmiotrace module [V38,21/29] Lock down /proc/kcore [V38,22/29] Lock down tracing and perf kprobes when in confidentiality mode [V38,23/29] bpf: Restrict bpf when kernel lockdown is in confidentiality mode [V38,24/29] Lock down perf when in confidentiality mode [V38,25/29] kexec: Allow kexec_file() with appropriate IMA policy when locked down [V38,26/29] debugfs: Restrict debugfs when the kernel is locked down [V38,27/29] tracefs: Restrict tracefs when the kernel is locked down [V38,28/29] efi: Restrict efivar_ssdt_load when the kernel is locked down [V38,29/29] lockdown: Print current->comm in restriction messages

Message ID

20190808000721.124691-19-matthewgarrett@google.com (mailing list archive)

State

New, archived

Headers

Date: Wed,  7 Aug 2019 17:07:10 -0700
In-Reply-To: <20190808000721.124691-1-matthewgarrett@google.com>
Message-Id: <20190808000721.124691-19-matthewgarrett@google.com>
Mime-Version: 1.0
References: <20190808000721.124691-1-matthewgarrett@google.com>
Subject: [PATCH V38 18/29] Lock down TIOCSSERIAL
From: Matthew Garrett <matthewgarrett@google.com>
To: jmorris@namei.org
Cc: linux-security-module@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-api@vger.kernel.org,
        David Howells <dhowells@redhat.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Matthew Garrett <mjg59@google.com>,
        Kees Cook <keescook@chromium.org>,
        Jiri Slaby <jslaby@suse.com>, linux-serial@vger.kernel.org
Content-Type: text/plain; charset="UTF-8"
Sender: owner-linux-security-module@vger.kernel.org
Precedence: bulk

Series

security: Add support for locking down the kernel | expand

Commit Message

Matthew Garrett Aug. 8, 2019, 12:07 a.m. UTC

From: David Howells <dhowells@redhat.com>

Lock down TIOCSSERIAL as that can be used to change the ioport and irq
settings on a serial port.  This only appears to be an issue for the serial
drivers that use the core serial code.  All other drivers seem to either
ignore attempts to change port/irq or give an error.

Reported-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Matthew Garrett <mjg59@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
cc: Jiri Slaby <jslaby@suse.com>
Cc: linux-serial@vger.kernel.org
---
 drivers/tty/serial/serial_core.c | 5 +++++
 include/linux/security.h         | 1 +
 security/lockdown/lockdown.c     | 1 +
 3 files changed, 7 insertions(+)

diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
index 4223cb496764..6e713be1d4e9 100644
--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c
@@ -22,6 +22,7 @@ 
 #include <linux/serial_core.h>
 #include <linux/delay.h>
 #include <linux/mutex.h>
+#include <linux/security.h>
 
 #include <linux/irq.h>
 #include <linux/uaccess.h>
@@ -862,6 +863,10 @@  static int uart_set_info(struct tty_struct *tty, struct tty_port *port,
 		goto check_and_exit;
 	}
 
+	retval = security_locked_down(LOCKDOWN_TIOCSSERIAL);
+	if (retval && (change_irq || change_port))
+		goto exit;
+
 	/*
 	 * Ask the low level driver to verify the settings.
 	 */
diff --git a/include/linux/security.h b/include/linux/security.h
index 3773ad09b831..8f7048395114 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -112,6 +112,7 @@  enum lockdown_reason {
 	LOCKDOWN_MSR,
 	LOCKDOWN_ACPI_TABLES,
 	LOCKDOWN_PCMCIA_CIS,
+	LOCKDOWN_TIOCSSERIAL,
 	LOCKDOWN_INTEGRITY_MAX,
 	LOCKDOWN_CONFIDENTIALITY_MAX,
 };
diff --git a/security/lockdown/lockdown.c b/security/lockdown/lockdown.c
index 22482e1b9a77..00a3a6438dd2 100644
--- a/security/lockdown/lockdown.c
+++ b/security/lockdown/lockdown.c
@@ -27,6 +27,7 @@  static char *lockdown_reasons[LOCKDOWN_CONFIDENTIALITY_MAX+1] = {
 	[LOCKDOWN_MSR] = "raw MSR access",
 	[LOCKDOWN_ACPI_TABLES] = "modifying ACPI tables",
 	[LOCKDOWN_PCMCIA_CIS] = "direct PCMCIA CIS storage",
+	[LOCKDOWN_TIOCSSERIAL] = "reconfiguration of serial port IO",
 	[LOCKDOWN_INTEGRITY_MAX] = "integrity",
 	[LOCKDOWN_CONFIDENTIALITY_MAX] = "confidentiality",
 };

[V38,18/29] Lock down TIOCSSERIAL

Commit Message

Patch