The patch below does not apply to the 5.4-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 b91cfb2573aeb5ab426fc3c35bcfe9e0d2a7ecbc Mon Sep 17 00:00:00 2001
From: Johan Hovold johan@kernel.org Date: Wed, 7 Apr 2021 12:23:32 +0200 Subject: [PATCH] tty: mxser: fix TIOCSSERIAL permission check
Changing the port type and closing_wait parameter are privileged operations so make sure to return -EPERM if a regular user tries to change them.
Note that the closing_wait parameter would not actually have been changed but the return value did not indicate that.
Cc: stable@vger.kernel.org Signed-off-by: Johan Hovold johan@kernel.org Link: https://lore.kernel.org/r/20210407102334.32361-15-johan@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
diff --git a/drivers/tty/mxser.c b/drivers/tty/mxser.c index 914b23071961..2d8e76263a25 100644 --- a/drivers/tty/mxser.c +++ b/drivers/tty/mxser.c @@ -1270,6 +1270,7 @@ static int mxser_set_serial_info(struct tty_struct *tty, if (!capable(CAP_SYS_ADMIN)) { if ((ss->baud_base != info->baud_base) || (close_delay != info->port.close_delay) || + (closing_wait != info->port.closing_wait) || ((ss->flags & ~ASYNC_USR_MASK) != (info->port.flags & ~ASYNC_USR_MASK))) { mutex_unlock(&port->mutex); return -EPERM; @@ -1296,11 +1297,11 @@ static int mxser_set_serial_info(struct tty_struct *tty, baud = ss->baud_base / ss->custom_divisor; tty_encode_baud_rate(tty, baud, baud); } - }
- info->type = ss->type; + info->type = ss->type;
- process_txrx_fifo(info); + process_txrx_fifo(info); + }
if (tty_port_initialized(port)) { if (flags != (port->flags & ASYNC_SPD_MASK)) {