[PATCH] usb: Fix regression caused by invalid ep0 maxpacket in virtual SuperSpeed device

Alan Stern
2024-04-30T14:33:55Z

A virtual SuperSpeed device in the FreeBSD BVCP package
(https://bhyve.npulse.net/) presents an invalid ep0 maxpacket size of 256.
It stopped working with Linux following a recent commit because now we
check these sizes more carefully than before.

Fix this regression by using the bMaxpacketSize0 value in the device
descriptor for SuperSpeed or faster devices, even if it is invalid. This
is a very simple-minded change; we might want to check more carefully for
values that actually make some sense (for instance, no smaller than 64).

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Reported-and-tested-by: Roger Whittaker <roger.whittaker@suse.com>
Closes: https://bugzilla.suse.com/show_bug.cgi?id=1220569
Link: https://lore.kernel.org/linux-usb/9efbd569-7059-4575-983f-0ea30df41871@suse.com/
Fixes: 59cf44575456 ("USB: core: Fix oversight in SuperSpeed initialization")
Cc: stable@vger.kernel.org

---

drivers/usb/core/hub.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)

Index: usb-devel/drivers/usb/core/hub.c
===================================================================
--- usb-devel.orig/drivers/usb/core/hub.c
+++ usb-devel/drivers/usb/core/hub.c
@@ -5110,9 +5110,10 @@ hub_port_init(struct usb_hub *hub, struc
}
if (usb_endpoint_maxp(&udev->ep0.desc) == i) {
; /* Initial ep0 maxpacket guess is right */
- } else if ((udev->speed == USB_SPEED_FULL ||
+ } else if (((udev->speed == USB_SPEED_FULL ||
udev->speed == USB_SPEED_HIGH) &&
- (i == 8 || i == 16 || i == 32 || i == 64)) {
+ (i == 8 || i == 16 || i == 32 || i == 64)) ||
+ (udev->speed >= USB_SPEED_SUPER && i > 0)) {
/* Initial guess is wrong; use the descriptor's value */
if (udev->speed == USB_SPEED_FULL)
dev_dbg(&udev->dev, "ep0 maxpacket = %d\n", i);