Bug 207327

Summary:	Hang when reading encrypted DVD
Product:	Drivers	Reporter:	Tom Horsley (horsley1953)
Component:	USB	Assignee:	Default virtual assignee for Drivers/USB (drivers_usb)
Status:	NEW ---
Severity:	normal
Priority:	P1
Hardware:	All
OS:	Linux
See Also:	https://bugzilla.redhat.com/show_bug.cgi?id=1822948
Kernel Version:	5.5.15-200.fc31.x86_64	Subsystem:
Regression:	No	Bisected commit-id:

Description Tom Horsley 2020-04-17 17:34:56 UTC

This redhat bug has a huge collection of comments analyzing the problem.

https://bugzilla.redhat.com/show_bug.cgi?id=1822948

It comes down to two issues:

1. Reading an encrypted sector on a commercial movie DVD simply generates a scsi error with a directly connected sata drive, but put that same drive in an external USB enclosure and read the same sector, and the read seems to hang and leave the drive unusable.

2. systemd-udevd apparently decides to randomly read sectors, thus causing the drive to be useless as soon as you insert a movie DVD.

Probably udevd shouldn't be doing that, but it also seems like it should be getting an error rather than a hung process, which seems like a kernel bug (unless it is a fundamental flaw in usb enclosures. I tried two different ones with the same results, though they may be using the same chipset).

Comment 99 in the redhat bug has a somewhat more detailed summary:

https://bugzilla.redhat.com/show_bug.cgi?id=1822948#c99