Commit 93fa08e9 authored Sep 07, 2021 by Johan Hovold Committed by Greg Kroah-Hartman Sep 30, 2021

USB: cdc-acm: fix minor-number release



commit 91fac0741d4817945c6ee0a17591421e7f5ecb86 upstream.

If the driver runs out of minor numbers it would release minor 0 and
allow another device to claim the minor while still in use.

Fortunately, registering the tty class device of the second device would
fail (with a stack dump) due to the sysfs name collision so no memory is
leaked.

Fixes: cae2bc76 ("usb: cdc-acm: Decrement tty port's refcount if probe() fail")
Cc: stable@vger.kernel.org      # 4.19
Cc: Jaejoong Kim <climbbb.kim@gmail.com>
Acked-by: Oliver Neukum <oneukum@suse.com>
Signed-off-by: Johan Hovold <johan@kernel.org>
Link: https://lore.kernel.org/r/20210907082318.7757-1-johan@kernel.org


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent 0dc1cfa7

drivers/usb/class/cdc-acm.c

+5 −2

Original line number	Diff line number	Diff line
		@@ -725,6 +725,7 @@ static void acm_port_destruct(struct tty_port *port)
		{
		struct acm *acm = container_of(port, struct acm, port);

		if (acm->minor != ACM_MINOR_INVALID)
		acm_release_minor(acm);
		usb_put_intf(acm->control);
		kfree(acm->country_codes);
		@@ -1356,8 +1357,10 @@ static int acm_probe(struct usb_interface *intf,
		usb_get_intf(acm->control); /* undone in destruct() */

		minor = acm_alloc_minor(acm);
		if (minor < 0)
		if (minor < 0) {
		acm->minor = ACM_MINOR_INVALID;
		goto alloc_fail1;
		}

		acm->minor = minor;
		acm->dev = usb_dev;

drivers/usb/class/cdc-acm.h

+2 −0

Original line number	Diff line number	Diff line
		@@ -22,6 +22,8 @@
		#define ACM_TTY_MAJOR 166
		#define ACM_TTY_MINORS 256

		#define ACM_MINOR_INVALID ACM_TTY_MINORS

		/*
		* Requests.
		*/