This is a note to let you know that I've just added the patch titled
serial_core: Check for port state when tty is in error state
to my tty git tree which can be found at
git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty.git
in the tty-testing branch.
The patch will show up in the next release of the linux-next tree
(usually sometime within the next 24 hours during the week.)
The patch will be merged to the tty-next branch sometime soon,
after it passes testing, and the merge window is open.
If you have any questions about this process, please let me know.
>From 2f70e49ed860020f5abae4f7015018ebc10e1f0e Mon Sep 17 00:00:00 2001
From: Alexey Kardashevskiy <aik@xxxxxxxxx>
Date: Thu, 3 Dec 2020 16:58:34 +1100
Subject: serial_core: Check for port state when tty is in error state
At the moment opening a serial device node (such as /dev/ttyS3)
succeeds even if there is no actual serial device behind it.
Reading/writing/ioctls fail as expected because the uart port is not
initialized (the type is PORT_UNKNOWN) and the TTY_IO_ERROR error state
bit is set fot the tty.
However setting line discipline does not have these checks
8250_port.c (8250 is the default choice made by univ8250_console_init()).
As the result of PORT_UNKNOWN, uart_port::iobase is NULL which
a platform translates onto some address accessing which produces a crash
like below.
This adds tty_port_initialized() to uart_set_ldisc() to prevent the crash.
Found by syzkaller.
Signed-off-by: Alexey Kardashevskiy <aik@xxxxxxxxx>
Link: https://lore.kernel.org/r/20201203055834.45838-1-aik@xxxxxxxxx
Cc: stable <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/tty/serial/serial_core.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
index f41cba10b86b..828f9ad1be49 100644
--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c
@@ -1467,6 +1467,10 @@ static void uart_set_ldisc(struct tty_struct *tty)
{
struct uart_state *state = tty->driver_data;
struct uart_port *uport;
+ struct tty_port *port = &state->port;
+
+ if (!tty_port_initialized(port))
+ return;
mutex_lock(&state->port.mutex);
uport = uart_port_check(state);
--
2.29.2
