[PATCH AUTOSEL 6.10 46/70] serial: protect uart_port_dtr_rts() in uart_shutdown() too

Sasha Levin
2024-10-04T18:23:30Z

From: "Jiri Slaby (SUSE)" <jirislaby@kernel.org>

[ Upstream commit 602babaa84d627923713acaf5f7e9a4369e77473 ]

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@kernel.org>
Cc: Peter Hurley <peter@hurleysoftware.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Link: https://lore.kernel.org/r/20240805102046.307511-3-jirislaby@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
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 9967444eae10c..dcd04db0e3eee 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);
}
--
2.43.0