| Message ID | 20240912141916.1044393-1-oneukum@suse.com (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | b41c1fa155ba56d125885b0191aabaf3c508d0a3 |
| Headers | show |
| Series | USB: class: CDC-ACM: fix race between get_serial and set_serial | expand |
diff --git a/drivers/usb/class/cdc-acm.c b/drivers/usb/class/cdc-acm.c index 0c1b69d944ca..605fea461102 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; }
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 <oneukum@suse.com> Fixes: 99f75a1fcd865 ("cdc-acm: switch to ->[sg]et_serial()") --- drivers/usb/class/cdc-acm.c | 2 ++ 1 file changed, 2 insertions(+)