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serial_core: Check for port state when tty is in error state 

commit 2f70e49ed8 upstream.

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@ozlabs.ru>
Link: https://lore.kernel.org/r/20201203055834.45838-1-aik@ozlabs.ru
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
5.4-rM2-2.2.x-imx-squashed
Alexey Kardashevskiy 2020-12-03 16:58:34 +11:00 committed by Greg Kroah-Hartman
parent 863cab3017
commit cda2f222e7
1 changed files with 4 additions and 0 deletions
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4
drivers/tty/serial/serial_core.c
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@ -1465,6 +1465,10 @@ 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);