host mode enumeration halts if configuration descriptor too long

[cleverca22]

Operating System

Linux

Board

rpi2

Firmware

custom https://github.com/librerpi/lk-overlay/tree/master/platform/bcm28xx/dwc2 + https://github.com/librerpi/lk-overlay/tree/master/lib/tinyusb

What happened ?

TU_ASSERT(total_len <= CFG_TUH_ENUMERATION_BUFSIZE, );
during enumeration, tinyusb will check if a config descriptor fits into the available buffer space
a usb webcam has a config descriptor over 1024 bytes, but the buffer is only 512 bytes

due to this assert, tinyusb just grinds to a halt, and stops enumerating, when it could have just left the device unconfigured and move to the next usb port

How to reproduce ?

connect something with a large config descriptor(a webcam for example) to a tinyusb host (any board/firmware should work)

Debug Log as txt file (LOG/CFG_TUSB_DEBUG=2)

process_enumeration() daddr=2 state=9
Get Configuration[0] Descriptor (9 bytes)
[0:2] Get Descriptor: 80 06 00 02 00 00 09 00 
 37.643664 [DWC2:hcd_setup_send:346]:   HOST0 SETUP 2.00 0xc4014d70/8 opep:0xc411418c
dumping channel 0
  HCCHAR0: 0x900008
    mps:8 ep:0 dir0 type:0 mc:1 addr:2
  HCSPLT0: 0x0
  HCINT0: 0x0
  HCINTMSK0: 0x7ff
  HCTSIZ0: 0x20000008
    size:8 packets:0 pid:1 ping:0
  HCDMA0: 0x0
 37.669686 [DWC2:dwc_check_interrupt:603]: hcd_event_xfer_complete(2, 0x0, 8, success, true)
 37.677843 [DWC2:dwc_irq:644]: irq time: 25849
on EP 00 with 8 bytes: OK
 37.792983 [DWC2:hcd_edpt_xfer:368]:    HOST0  <-   2.80 0xc4014d88/9 opep:0xc411418c type:0 pid:153
 38.801206 [DWC2:dwc_check_interrupt:500]: hcd_event_xfer_complete(2, 0x80, 9, success, true)
 38.807972 [DWC2:dwc_irq:644]: irq time: 6766
on EP 80 with 9 bytes: OK
[0:2] Control data:
  0000:  09 02 95 05 04 01 00 80 FA                       |.........|
 38.832633 [DWC2:hcd_edpt_xfer:376]:    HOST0  ->   2.00 0x0/0 opep:0xc411418c
dumping channel 0
  HCCHAR0: 0x900008
    mps:8 ep:0 dir0 type:0 mc:1 addr:2
  HCSPLT0: 0x0
  HCINT0: 0x0
  HCINTMSK0: 0x7ff
  HCTSIZ0: 0x0
    size:0 packets:0 pid:0 ping:0
  HCDMA0: 0x0
 38.855877 [DWC2:dwc_check_interrupt:603]: hcd_event_xfer_complete(2, 0x0, 0, success, true)
 38.864034 [DWC2:dwc_irq:644]: irq time: 25230
on EP 00 with 0 bytes: OK

process_enumeration() daddr=2 state=10
ENUM_GET_FULL_CONFIG_DESC
config size: 1429 vs 512
process_enumeration 1426: ASSERT FAILED

it successfully fetched the first 9 bytes of the config descriptor, noticed the size wont fit, and then gave up

Screenshots

No response

I have checked existing issues, dicussion and documentation

• I confirm I have checked existing issues, dicussion and documentation.

[hathach]

the fix is obvious, increase the configure buffer

[cleverca22]

@hathach but is that really effective, when you dont want to support such a device, and you can never know how big the buffer will need to be?

you always run the risk of your host-mode device breaking, because the user plugged in something with a bigger descriptor then you planned for

for context:
i want to use tinyusb on an rpi, to access MSD and keyboard
and i dont want a surprise webcam to break things, due to a fat descriptor
but if i just make it 2kb, it can still break when a bigger descriptor comes along
how big does it need to be? or should tinyusb just skip the device and avoid the problem

[hathach]

Ah i see, I skip the part where the host skip entirely rest of the hub. You are right, it should just skip device and continue though.

PS: I thought you want to support that webcam :D