From: Johan Hovold johan@kernel.org
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: cae2bc768d17 ("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 --- drivers/usb/class/cdc-acm.c | 7 +++++-- drivers/usb/class/cdc-acm.h | 2 ++ 2 files changed, 7 insertions(+), 2 deletions(-)
--- a/drivers/usb/class/cdc-acm.c +++ b/drivers/usb/class/cdc-acm.c @@ -726,7 +726,8 @@ static void acm_port_destruct(struct tty { 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); @@ -1343,8 +1344,10 @@ made_compressed_probe: 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; --- a/drivers/usb/class/cdc-acm.h +++ b/drivers/usb/class/cdc-acm.h @@ -22,6 +22,8 @@ #define ACM_TTY_MAJOR 166 #define ACM_TTY_MINORS 256
+#define ACM_MINOR_INVALID ACM_TTY_MINORS + /* * Requests. */