[PATCH 02/13] serial: protect uart_port_dtr_rts() in uart_shutdown() too

From: Jiri Slaby (SUSE)
Date: Mon Aug 05 2024 - 06:23:17 EST


Commit af224ca2df29 (serial: core: Prevent unsafe uart port access, part
3) added few uport == NULL checks. It added one to uart_shutdown(), so
the commit assumes, uport can be NULL in there. But right after that
protection, there is an unprotected "uart_port_dtr_rts(uport, false);"
call. That is invoked only if HUPCL is set, so I assume that is the
reason why we do not see lots of these reports.

Or it cannot be NULL at this point at all for some reason :P.

Until the above is investigated, stay on the safe side and move this
dereference to the if too.

I got this inconsistency from Coverity under CID 1585130. Thanks.

Signed-off-by: Jiri Slaby (SUSE) <jirislaby@xxxxxxxxxx>
Cc: Peter Hurley <peter@xxxxxxxxxxxxxxxxxx>
Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/tty/serial/serial_core.c | 16 +++++++++-------
1 file changed, 9 insertions(+), 7 deletions(-)

diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
index 61c7e1268957..3afe77f05abf 100644
--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c
@@ -407,14 +407,16 @@ static void uart_shutdown(struct tty_struct *tty, struct uart_state *state)
/*
* Turn off DTR and RTS early.
*/
- if (uport && uart_console(uport) && tty) {
- uport->cons->cflag = tty->termios.c_cflag;
- uport->cons->ispeed = tty->termios.c_ispeed;
- uport->cons->ospeed = tty->termios.c_ospeed;
- }
+ if (uport) {
+ if (uart_console(uport) && tty) {
+ uport->cons->cflag = tty->termios.c_cflag;
+ uport->cons->ispeed = tty->termios.c_ispeed;
+ uport->cons->ospeed = tty->termios.c_ospeed;
+ }

- if (!tty || C_HUPCL(tty))
- uart_port_dtr_rts(uport, false);
+ if (!tty || C_HUPCL(tty))
+ uart_port_dtr_rts(uport, false);
+ }

uart_port_shutdown(port);
}
--
2.46.0