| Message ID | 20190622000358.19895-19-matthewgarrett@google.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Lockdown as an LSM | expand |
On Fri, Jun 21, 2019 at 05:03:47PM -0700, Matthew Garrett wrote: > 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> > 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 351843f847c0..a84f231a5df4 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> > @@ -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 || This should be moved after the capable test. With that fixed: Reviewed-by: Kees Cook <keescook@chromium.org> -Kees > 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 >
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 <linux/serial_core.h> #include <linux/delay.h> #include <linux/mutex.h> +#include <linux/security.h> #include <linux/irq.h> #include <linux/uaccess.h> @@ -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", };