From mboxrd@z Thu Jan 1 00:00:00 1970 From: Matthew Garrett Subject: [PATCH V34 18/29] Lock down TIOCSSERIAL Date: Fri, 21 Jun 2019 17:03:47 -0700 Message-ID: <20190622000358.19895-19-matthewgarrett@google.com> References: <20190622000358.19895-1-matthewgarrett@google.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Return-path: In-Reply-To: <20190622000358.19895-1-matthewgarrett@google.com> Sender: linux-kernel-owner@vger.kernel.org To: jmorris@namei.org Cc: linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org, linux-api@vger.kernel.org, David Howells , Greg Kroah-Hartman , Matthew Garrett , Jiri Slaby , linux-serial@vger.kernel.org List-Id: linux-api@vger.kernel.org From: David Howells 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 Signed-off-by: David Howells Signed-off-by: Matthew Garrett cc: Jiri Slaby 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 351843f847c0..a84f231a5df4 100644 --- a/drivers/tty/serial/serial_core.c +++ b/drivers/tty/serial/serial_core.c @@ -22,6 +22,7 @@ #include #include #include +#include #include #include @@ -852,6 +853,10 @@ static int uart_set_info(struct tty_struct *tty, struct tty_port *port, new_flags = (__force upf_t)new_info->flags; old_custom_divisor = uport->custom_divisor; + retval = security_locked_down(LOCKDOWN_TIOCSSERIAL); + if (retval && (change_port || change_irq)) + goto exit; + if (!capable(CAP_SYS_ADMIN)) { retval = -EPERM; if (change_irq || change_port || diff --git a/include/linux/security.h b/include/linux/security.h index 03c125b277ca..61e3f4a62d16 100644 --- a/include/linux/security.h +++ b/include/linux/security.h @@ -91,6 +91,7 @@ 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 7be3e8fb5847..c89046dc2155 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] = "modified ACPI tables", [LOCKDOWN_PCMCIA_CIS] = "direct PCMCIA CIS storage", + [LOCKDOWN_TIOCSSERIAL] = "reconfiguration of serial port IO", [LOCKDOWN_INTEGRITY_MAX] = "integrity", [LOCKDOWN_CONFIDENTIALITY_MAX] = "confidentiality", }; -- 2.22.0.410.gd8fdbe21b5-goog