When fetching the first descriptor from a new device, only validate that we received at least 8 bytes, not that we received the entire descriptor. The reasoning is: - The code only uses fields in the first 8 bytes, so that's all we need to have fetched at this stage. - The smallest maxpacket size is 8 bytes. Before we know the actual maxpacket the device uses, the USB controller may only accept a single packet (see the DWC2 note in the comment added in the commit). Consequently we are only guaranteed to receive 1 packet (at least 8 bytes) even in a non-error case.

Fixes: 1a7758044b04 ("usb: Early failure when the first descriptor read fails or is invalid") Cc: Paul Kocialkowski contact@paulk.fr Signed-off-by: Stephen Warren swarren@wwwdotorg.org --- common/usb.c | 17 ++++++++++++++++- 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/common/usb.c b/common/usb.c index f6488475a7f2..bf76c4159341 100644 --- a/common/usb.c +++ b/common/usb.c @@ -956,7 +956,22 @@ int usb_new_device(struct usb_device *dev) */ #ifndef CONFIG_USB_XHCI err = usb_get_descriptor(dev, USB_DT_DEVICE, 0, desc, 64); - if (err < sizeof(struct usb_device_descriptor)) { + /* + * Validate we've received only at least 8 bytes, not that we've + * received the entire descriptor. The reasoning is: + * - The code only uses fields in the first 8 bytes, so that's all we + * need to have fetched at this stage. + * - The smallest maxpacket size is 8 bytes. Before we know the actual + * maxpacket the device uses, the USB controller may only accept a + * single packet. Consequently we are only guaranteed to receive 1 + * packet (at least 8 bytes) even in a non-error case. + * + * At least the DWC2 controller needs to be programmed with the number + * of packets in addition to the number of bytes. A request for 64 + * bytes of data with the maxpacket guessed as 64 (above) yields a + * request for 1 packet. + */ + if (err < 8) { debug("usb_new_device: usb_get_descriptor() failed\n"); return -EIO; }