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lockdown: Lock down TIOCSSERIAL

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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
Signed-off-by: James Morris <jmorris@namei.org>
This commit is contained in:
David Howells 2019-08-19 17:17:54 -07:00 committed by James Morris
parent 3f19cad3fa
commit 794edf30ee
3 changed files with 7 additions and 0 deletions
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5
drivers/tty/serial/serial_core.c
View File

@ -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.
*/

1
include/linux/security.h
View File

@ -112,6 +112,7 @@ enum lockdown_reason {
LOCKDOWN_MSR,
LOCKDOWN_ACPI_TABLES,
LOCKDOWN_PCMCIA_CIS,
LOCKDOWN_TIOCSSERIAL,
LOCKDOWN_INTEGRITY_MAX,
LOCKDOWN_CONFIDENTIALITY_MAX,
};

1
security/lockdown/lockdown.c
View File

@ -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",
};