stress-ng procfs test triggers kernel bug in mm/usercopy.c

[Jeffrey Bastian <jbastian@xxxxxxxxxx>]

I just opened a BZ for "kernel BUG at mm/usercopy.c:99!" while running
the stress-ng procfs stressor on the 5.10.0-rc1 kernel:

https://bugzilla.kernel.org/show_bug.cgi?id=209919

It's easily reproducible on x86_64 and arm64 (aarch64) systems.  I'm
testing on ppc64le and s390x next.

--
Jeff Bastian
Kernel QE - Hardware Enablement
Red Hat