USBMSC reports repeated "USB UNPLUGGED" and can cause stack corruption

[savejeff]

Board

ESP32-S3 DevKitC-1

Device Description

Plane ESP32-S3 DevKitC-1

Hardware Configuration

no peripheral attached

Version

v2.0.4

IDE Name

Arduini IDE

Operating System

Windows 10

Flash frequency

80Mhz

PSRAM enabled

yes

Upload speed

921600

Description

There seems to be a bug in the USB MSC implementation. When the native USB Port is not connected to a USB Host (aka a Laptop/PC) it repeatedly fires the USB UNPLUGGED event. as the event queue is only 5 long, this can cause the code to crash with stack canary when there is enough other code running.

This can be easily reproduced by powering an ESP32-S3 (for example over the "UART" USB port on the devkit) and not connecting or disconnecting the "USB" USB Port.

I found a mention of a similar problem with the ESP32-S2 here and here

Sketch

unchanged USBMSC.ino example

Debug Message

USB UNPLUGGED <- this one is fired immediately
USB UNPLUGGED <- after a second the repeated event start
USB UNPLUGGED
USB UNPLUGGED
USB UNPLUGGED
USB UNPLUGGED
USB UNPLUGGED
USB UNPLUGGED
USB UNPLUGGED
USB UNPLUGGED
USB UNPLUGGED
USB UNPLUGGED
USB UNPLUGGED
USB UNPLUGGED
USB UNPLUGGED
USB UNPLUGGED
USB UNPLUGGED
USB UNPLUGGED
USB UNPLUGGED
USB UNPLUGGED
USB UNPLUGGED
USB UNPLUGGED
USB UNPLUGGED
USB UNPLUGGED
USB UNPLUGGED

Guru Meditation Error: Core  0 panic'ed (Unhandled debug exception). 
Debug exception reason: Stack canary watchpoint triggered (arduino_usb_eve) 
Core  0 register dump:
PC      : 0x40378413  PS      : 0x00060136  A0      : 0x00060130  A1      : 0x3fcf2130  
A2      : 0x3fcf2984  A3      : 0x3fcf2530  A4      : 0x3fcf241c  A5      : 0x00000000  
A6      : 0x00000001  A7      : 0x3fcf2454  A8      : 0x00000000  A9      : 0x00000001  
A10     : 0xa0000000  A11     : 0x00000000  A12     : 0x40000000  A13     : 0x00000000  
A14     : 0x02c92bd0  A15     : 0x00ffffff  SAR     : 0x00000004  EXCCAUSE: 0x00000001  
EXCVADDR: 0x00000000  LBEG    : 0x400556d5  LEND    : 0x400556e5  LCOUNT  : 0xffffffff  


Backtrace:0x40378410:0x3fcf21300x0006012d:0x3fcf2220  |<-CORRUPTED




ELF file SHA256: 0000000000000000

The stack canary can not be reproduced with the blank example code. I added this as an example exception that can happen when the event queue is not emptied fast enough.

Other Steps to Reproduce

The best way to reproduce the problem: 1.) connect both USB ports to the PC. 2.) Start the example code (a USB stick should be presented) 3.) disconnect the "USB" USB Port but leave the "UART" USB Port connected 4.) the USB UNPLUGGED will start to get printed repeatedly

I have checked existing issues, online documentation and the Troubleshooting Guide

• [X] I confirm I have checked existing issues, online documentation and Troubleshooting guide.

[savejeff]

@hathach Could you please look at this issue. I've seen you have investigated a similar issue before. Do you have an idea what could cause the USB UNPLUGGED event to be fired so rapidly? Help would be very appreciated!