serial: protect uart_port_dtr_rts() in uart_shutdown() too

[ 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>
[Adapted over commit 5701cb8bf50e ("tty: Call ->dtr_rts() parameter
active consistently") not in the tree]
Signed-off-by: Tomas Krcka <krckatom@amazon.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
index c7adcf97e2a33aef29f2d47fceb1d5ae0f491bb8..6d7d448d0fbf56464fe88068ec6551f277f95160 100644 (file)
--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c
@@ -286,14 +286,16 @@ 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, 0);
+                       if (!tty || C_HUPCL(tty))
+                               uart_port_dtr_rts(uport, 0);
+               }
 
                uart_port_shutdown(port);
        }