serial: core: fix TIOCSSERIAL and TIOCSERCONFIG on uninitialised ports

Commit 8ca59f7baee7 ("serial: fix ioctl hangup race") made
uart_set_info() and uart_do_autoconfig() return -EIO when TTY_IO_ERROR
is set, so that they do not run on a port that has been hung up.

However, TTY_IO_ERROR is also set on a port that could not be started,
for example because its type is unknown, and by uart_shutdown(), which
both functions call. As of now, setserial cannot configure a port that
the kernel did not detect, and an autoconfig that follows a port, irq or
type change in the same setserial call fails on any port.

The issue can be reproduced with setserial (busybox) on a port without
a detected UART, for example ttyS3 of a QEMU guest:

    setserial /dev/ttyS3 uart 16550A
    setserial -g /dev/ttyS3

Before commit 8ca59f7baee7 ("serial: fix ioctl hangup race"), the
result is:

    /dev/ttyS3, UART: 16550A, Port: 0x02e8, IRQ: 3

After that commit, the result is:

    setserial: can't set serial info: Input/output error
    /dev/ttyS3, UART: unknown, Port: 0x02e8, IRQ: 3

This patch will check tty_port_active() in these two functions instead.
uart_hangup() clears it under the port mutex, and it stays set on an
open port that could not be started.

Fixes: 8ca59f7baee7 ("serial: fix ioctl hangup race")
Cc: stable@kernel.org
Signed-off-by: Hengyu Liang <hengyul@cs.unc.edu>
Tested-by: Johan Hovold <johan@kernel.org>
Reviewed-by: Johan Hovold <johan@kernel.org>
Link: https://patch.msgid.link/20261010034616.3915864-1-hengyul@cs.unc.edu
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

0 files changed, 0 insertions, 0 deletions