Bug 203937

Summary:	Program that sets FS register makes a Linux Hyper-V Instance crash
Product:	Virtualization	Reporter:	Jong Hyun Park (jonhpark7966)
Component:	kvm	Assignee:	virtualization_kvm
Status:	RESOLVED PATCH_ALREADY_AVAILABLE
Severity:	normal	CC:	Tianyu.Lan
Priority:	P1
Hardware:	x86-64
OS:	Linux
Kernel Version:	4.19-rc1	Subsystem:
Regression:	No	Bisected commit-id:

Description Jong Hyun Park 2019-06-20 01:12:56 UTC

I found out that a simple program makes a Linux Hyper-V instance crash.

The program that crashes.
- it is simple. creates threads, sets ldt entry, stores it to fs register, and does simple work.
- you can find it on my github. (https://github.com/jonhpark7966/test_codes)

Linux versions that is installed over hyper-v
- 4.18.20 has no problem, but 4.19-rc1 crashes
- 64bit also has no probelm, but 32bit crashes


Thanks,

Jong Hyun Park

Comment 1 Jong Hyun Park 2019-07-16 02:03:13 UTC

I tested with "nopti" option as a kernel parameter, then this problem does not happen.

I asked to Tianyu Lan <Tianyu.Lan@microsoft.com> about this issue,
because he commited some codes about hyper-v at 4.19-rc1 version.
He noticed me about this page table isolation issues. thanks to Lan.

Comment 2 Jong Hyun Park 2019-07-18 01:28:16 UTC

I also tested on vmware, but it works well.

Comment 3 Tianyu Lan 2019-10-11 02:48:12 UTC

The issue has been fixed in v5.3 by commit 4030b4c58 x86/hyper-v: Fix overflow bug in fill_gva_list().

Comment 4 Jong Hyun Park 2019-10-11 08:37:42 UTC

The issue has been resolved!