[Bug 1883398] [NEW] USB serial device passtrough causes qemu to segfault and kill the VM

[Launchpad Bug Tracker]

You have been subscribed to a public bug by Rafael David Tinoco (rafaeldtinoco):

What happens:

When I pass trough my CH340G (very common USB-TTL serial module) with
high-baud data coming in to my Windows 10 VM. qemu segfaults and dirtily
shuts down my VM at some random point. The higher the baudrate, the more
likely it is to happen. 921600 means the death to my VM in somewhere
between 10 seconds and a few minutes. There's no blue screen or
anything, it's qemu dying and taking the VM with it.

So far I've also determined:
* It does not crash as often on lower baudrates.

* It does not seem to crash if there's no data coming in.

* It does not matter if something is reading the data or not.

* It does not matter what software is reading the serial device.


What should happen:

Qemu shouldn't crash on a device being passed trough.

System details:

Host - Ubuntu 20.04, qemu-system-common 4.2-3ubuntu6.1 (and everything
else as well latest from repository)

VM - Windows 10, latest updates installed

Diagnostics info:

dmesg output:
[19511.277076] qemu-system-x86[35900]: segfault at 558c4c000000 ip 00007fee658ce8a2 sp 00007ffc6015f720 error 4 in libc-2.31.so[7fee65856000+178000]
[19511.277082] Code: a8 02 75 34 48 8b 15 f5 d4 14 00 64 48 83 3a 00 0f 84 9a 00 00 00 48 8d 3d eb e2 14 00 a8 04 74 0c 48 89 f0 48 25 00 00 00 fc <48>
8b 38 31 d2 48 83 c4 18 e9 10 c1 ff ff 8b 15 fe d9 14 00 85 d2

lsusb output (this is a CH340G module, very very widespread and cheap):
Bus 002 Device 018: ID 0403:6001 Future Technology Devices International, Ltd FT232 Serial (UART) IC

** Affects: qemu (Ubuntu)
     Importance: Undecided
         Status: Incomplete

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USB serial device passtrough causes qemu to segfault and kill the VM
https://bugs.launchpad.net/bugs/1883398
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