[PATCH 5.11 014/601] staging: fwserial: fix TIOCSSERIAL permission check

Greg Kroah-Hartman
2021-05-12T16:45:19Z

From: Johan Hovold <johan@kernel.org>

commit 2104eb283df66a482b60254299acbe3c68c03412 upstream.

Changing the port close-delay parameter is a privileged operation so
make sure to return -EPERM if a regular user tries to change it.

Fixes: 7355ba3445f2 ("staging: fwserial: Add TTY-over-Firewire serial driver")
Cc: stable@vger.kernel.org # 3.8
Signed-off-by: Johan Hovold <johan@kernel.org>
Link: https://lore.kernel.org/r/20210407102334.32361-3-johan@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/staging/fwserial/fwserial.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)

--- a/drivers/staging/fwserial/fwserial.c
+++ b/drivers/staging/fwserial/fwserial.c
@@ -1232,20 +1232,24 @@ static int set_serial_info(struct tty_st
struct serial_struct *ss)
{
struct fwtty_port *port = tty->driver_data;
+ unsigned int cdelay;

if (ss->irq != 0 || ss->port != 0 || ss->custom_divisor != 0 ||
ss->baud_base != 400000000)
return -EPERM;

+ cdelay = msecs_to_jiffies(ss->close_delay * 10);
+
mutex_lock(&port->port.mutex);
if (!capable(CAP_SYS_ADMIN)) {
- if (((ss->flags & ~ASYNC_USR_MASK) !=
+ if (cdelay != port->port.close_delay ||
+ ((ss->flags & ~ASYNC_USR_MASK) !=
(port->port.flags & ~ASYNC_USR_MASK))) {
mutex_unlock(&port->port.mutex);
return -EPERM;
}
}
- port->port.close_delay = msecs_to_jiffies(ss->close_delay * 10);
+ port->port.close_delay = cdelay;
mutex_unlock(&port->port.mutex);

return 0;