The patch below does not apply to the 4.9-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From 2104eb283df66a482b60254299acbe3c68c03412 Mon Sep 17 00:00:00 2001
From: Johan Hovold johan@kernel.org Date: Wed, 7 Apr 2021 12:23:20 +0200 Subject: [PATCH] staging: fwserial: fix TIOCSSERIAL permission check
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
diff --git a/drivers/staging/fwserial/fwserial.c b/drivers/staging/fwserial/fwserial.c index c963848522b1..440d11423812 100644 --- a/drivers/staging/fwserial/fwserial.c +++ b/drivers/staging/fwserial/fwserial.c @@ -1232,20 +1232,24 @@ static int set_serial_info(struct tty_struct *tty, 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;