From d2ac91ef877ff0c7462625671bc8d5710dbec791 Mon Sep 17 00:00:00 2001 From: Oliver Neukum Date: Thu, 12 Sep 2024 16:19:06 +0200 Subject: [PATCH] USB: class: CDC-ACM: fix race between get_serial and set_serial BugLink: https://bugs.launchpad.net/bugs/2089340 commit b41c1fa155ba56d125885b0191aabaf3c508d0a3 upstream. TIOCGSERIAL is an ioctl. Thus it must be atomic. It returns two values. Racing with set_serial it can return an inconsistent result. The mutex must be taken. In terms of logic the bug is as old as the driver. In terms of code it goes back to the conversion to the get_serial and set_serial methods. Signed-off-by: Oliver Neukum Cc: stable Fixes: 99f75a1fcd865 ("cdc-acm: switch to ->[sg]et_serial()") Link: https://lore.kernel.org/r/20240912141916.1044393-1-oneukum@suse.com Signed-off-by: Greg Kroah-Hartman Signed-off-by: Portia Stephens Signed-off-by: Stefan Bader --- drivers/usb/class/cdc-acm.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/drivers/usb/class/cdc-acm.c b/drivers/usb/class/cdc-acm.c index 0b016cd249ae..c786e947fba1 100644 --- a/drivers/usb/class/cdc-acm.c +++ b/drivers/usb/class/cdc-acm.c @@ -962,10 +962,12 @@ static int get_serial_info(struct tty_struct *tty, struct serial_struct *ss) struct acm *acm = tty->driver_data; ss->line = acm->minor; + mutex_lock(&acm->port.mutex); ss->close_delay = jiffies_to_msecs(acm->port.close_delay) / 10; ss->closing_wait = acm->port.closing_wait == ASYNC_CLOSING_WAIT_NONE ? ASYNC_CLOSING_WAIT_NONE : jiffies_to_msecs(acm->port.closing_wait) / 10; + mutex_unlock(&acm->port.mutex); return 0; }