Commit b41c1fa1 authored by Oliver Neukum's avatar Oliver Neukum Committed by Greg Kroah-Hartman
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USB: class: CDC-ACM: fix race between get_serial and set_serial 



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: default avatarOliver Neukum <oneukum@suse.com>
Cc: stable <stable@kernel.org>
Fixes: 99f75a1f ("cdc-acm: switch to ->[sg]et_serial()")
Link: https://lore.kernel.org/r/20240912141916.1044393-1-oneukum@suse.com


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 9ae0f262

drivers/usb/class/cdc-acm.c

+2 −0
Original line number Diff line number Diff line
@@ -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;

}