CPU stuck

[Dmitry Nagornykh]

CPU stuck were discovered at task hung in do_truncate. The problem was originally found by syzbot, https://syzkaller.appspot.com/bug?id=18b2ab4c697021ee8369. It is reproduced by the root user in the docker container or host on Ubuntu 20.04.3 LTS with Linux 5.4.0-91-generic. The bug reproducer is built from https://raw.githubusercontent.com/dvyukov/syzkaller-repros/master/linux/18b2ab4c697021ee8369.c.
It reproduces in Ubuntu 18.04.6 LTSwith Linux 4.15.0-163-generic and Ubuntu 20.04.3 LTS with Linux mainline v5.16-rc4 also. I used MSI GT72 6QD Dominator with i7-6820HK.

There are steps to reproduce in the Docker container:
-----------------------------------------------------------
docker pull ubuntu
docker run -ti ubuntu bash
apt update
apt install gcc wget
wget https://raw.githubusercontent.com/dvyukov/syzkaller-repros/master/linux/18b2ab4c697021ee8369.c
gcc ./18b2ab4c697021ee8369.c -static -pthread -o 18b2ab4c697021ee8369
./18b2ab4c697021ee8369

The kernel crash contains as a result:
----------------------------------------
root@de45b02a83c0:/# ./18b2ab4c697021ee8369
�� @cgroup.controllers�./file0[ 7977.039018] watchdog: BUG: soft lockup - CPU#1 stuck for 22s! [18b2ab4c697021e:4427]
[ 8005.212380] watchdog: BUG: soft lockup - CPU#1 stuck for 23s! [18b2ab4c697021e:4427]
[ 8012.900740] rcu: INFO: rcu_sched detected stalls on CPUs/tasks:
[ 8012.904199] rcu: 1-....: (148 ticks this GP) idle=db2/1/0x4000000000000004 softirq=30262/30262 fqs=7456
�� @cgroup.controllers�./file0�� @cgroup.controllers�./file0[ 8097.026740] watchdog: BUG: soft lockup - CPU#1 stuck for 22s! [apport:33113]
[ 8181.189733] watchdog: BUG: soft lockup - CPU#1 stuck for 23s! [kworker/1:0:1478]

ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: linux-image-5.4.0-91-generic 5.4.0-91.102
ProcVersionSignature: Ubuntu 5.4.0-91.102-generic 5.4.151
Uname: Linux 5.4.0-91-generic x86_64
AlsaDevices:
 total 0
 crw-rw---- 1 root audio 116, 1 Dec 7 14:39 seq
 crw-rw---- 1 root audio 116, 33 Dec 7 14:39 timer
AplayDevices: Error: [Errno 2] No such file or directory: 'aplay'
ApportVersion: 2.20.11-0ubuntu27.21
Architecture: amd64
ArecordDevices: Error: [Errno 2] No such file or directory: 'arecord'
AudioDevicesInUse: Error: command ['fuser', '-v', '/dev/snd/seq', '/dev/snd/timer'] failed with exit code 1:
CasperMD5CheckResult: pass
Date: Tue Dec 7 15:11:42 2021
InstallationDate: Installed on 2021-11-29 (8 days ago)
InstallationMedia: Ubuntu-Server 20.04.3 LTS "Focal Fossa" - Release amd64 (20210824)
IwConfig: Error: [Errno 2] No such file or directory: 'iwconfig'
Lsusb: Error: command ['lsusb'] failed with exit code 1:
Lsusb-t:

Lsusb-v: Error: command ['lsusb', '-v'] failed with exit code 1:
MachineType: QEMU Standard PC (i440FX + PIIX, 1996)
PciMultimedia:

ProcEnviron:
 TERM=vt220
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=C.UTF-8
 SHELL=/bin/bash
ProcFB: 0 bochs-drmdrmfb
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-5.4.0-91-generic root=UUID=2ad85404-d6b7-4c7d-a860-b873557a175c ro console=ttyS0 slub_debug=FZ crashkernel=256M
RelatedPackageVersions:
 linux-restricted-modules-5.4.0-91-generic N/A
 linux-backports-modules-5.4.0-91-generic N/A
 linux-firmware 1.187.20
RfKill: Error: [Errno 2] No such file or directory: 'rfkill'
SourcePackage: linux
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 04/01/2014
dmi.bios.vendor: SeaBIOS
dmi.bios.version: 1.13.0-1ubuntu1.1
dmi.chassis.type: 1
dmi.chassis.vendor: QEMU
dmi.chassis.version: pc-i440fx-focal
dmi.modalias: dmi:bvnSeaBIOS:bvr1.13.0-1ubuntu1.1:bd04/01/2014:svnQEMU:pnStandardPC(i440FX+PIIX,1996):pvrpc-i440fx-focal:cvnQEMU:ct1:cvrpc-i440fx-focal:
dmi.product.name: Standard PC (i440FX + PIIX, 1996)
dmi.product.version: pc-i440fx-focal
dmi.sys.vendor: QEMU

[Ubuntu Kernel Bot (ubuntu-kernel-bot)]

This change was made by a bot.