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USB: cdc-acm: fix minor-number release

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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: cae2bc768d ("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>
This commit is contained in:
Johan Hovold 2021-09-07 10:23:18 +02:00 committed by Greg Kroah-Hartman
parent 856e6e8e0f
commit 91fac0741d
2 changed files with 7 additions and 2 deletions
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7
drivers/usb/class/cdc-acm.c
View file

@ -726,7 +726,8 @@ static void acm_port_destruct(struct tty_port *port)
{
struct acm *acm = container_of(port, struct acm, port);
acm_release_minor(acm);
if (acm->minor != ACM_MINOR_INVALID)
acm_release_minor(acm);
usb_put_intf(acm->control);
kfree(acm->country_codes);
kfree(acm);
@ -1323,8 +1324,10 @@ 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 err_put_port;
}
acm->minor = minor;
acm->dev = usb_dev;

2
drivers/usb/class/cdc-acm.h
View file

@ -22,6 +22,8 @@
#define ACM_TTY_MAJOR 166
#define ACM_TTY_MINORS 256
#define ACM_MINOR_INVALID ACM_TTY_MINORS
/*
* Requests.
*/