qemu-system_x86_64 crashes when internal system mount virtio-9p

[Wei Tsui]

I'm using Ubuntu 16.04 amd64.

Host system executes command like:

    qemu-system-x86_64 -initrd ./hyper-initrd.img -kernel ./kernel -m 512 -smp 1 -fsdev local,id=virtio9p,path=`pwd`/rootfs,security_model=none -device virtio-9p-pci,fsdev=virtio9p,mount_tag=share_dir

Qemu Intern system executes API like:

    mkdir("/nfs", 0755);
    mount("share_dir", "/nfs", "9p", MS_MGC_VAL| MS_NODEV, "trans=virtio,cache=loose")

Then, external qemu-system_x86-64 crashes!

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: qemu-kvm 1:2.5+dfsg-1ubuntu3
ProcVersionSignature: Ubuntu 4.3.0-5.16-generic 4.3.3
Uname: Linux 4.3.0-5-generic x86_64
ApportVersion: 2.19.3-0ubuntu3
Architecture: amd64
CurrentDesktop: GNOME-Flashback
Date: Fri Jan 22 17:08:41 2016
JournalErrors:
MachineType: LENOVO ThinkCentre M8400t
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-4.3.0-5-generic root=UUID=da1b1143-7e41-4242-a0a5-5c5b748b3bfe ro quiet cgroup_enable=memory swapaccount=1
SourcePackage: qemu
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 09/17/2013
dmi.bios.vendor: LENOVO
dmi.bios.version: 9SKT75AUS
dmi.board.name: MAHOBAY
dmi.board.vendor: LENOVO
dmi.board.version: NOK
dmi.chassis.type: 3
dmi.chassis.vendor: LENOVO
dmi.chassis.version: None
dmi.modalias: dmi:bvnLENOVO:bvr9SKT75AUS:bd09/17/2013:svnLENOVO:pnThinkCentreM8400t:pvrLenovoProduct:rvnLENOVO:rnMAHOBAY:rvrNOK:cvnLENOVO:ct3:cvrNone:
dmi.product.name: ThinkCentre M8400t
dmi.product.version: Lenovo Product
dmi.sys.vendor: LENOVO

[Wei Tsui (ghostplant)]

A test script is appended.

This script works on Trusty, Utopic, Vivid and Wily, while crashes on Xenial.

[Wei Tsui (ghostplant)]

I think this the bug is caused by qemu 2.5 because I install qemu 2.3 (wily version) in to xernial (linux 4.4), and it doesn't crash.

[Serge Hallyn (serge-hallyn)]

Hi,

I just tested this in the new xenial package and it did not crash.

mounting 9p shared fs ..
inside_9pfs

BusyBox v1.22.1 (Ubuntu 1:1.22.0-15ubuntu1) built-in shell (ash)
Enter 'help' for a list of built-in commands.

# [ 2.858868] Switched to clocksource tsc

Could you check whether it has been fixed for you as well in
1:2.5+dfsg-5ubuntu1?

[Wei Tsui (ghostplant)]

Okay, version "2.5+dfsg-5ubuntu1" fix this bug, thanks!