Public bug reported:
Hi,
I'm reproducing a kernel bug in vmalloc_sync_all() with a 32-bit x86
kernel.
The problem appears in
Linux ubuntu 4.15.0-50-generic #54-Ubuntu SMP Mon May 6 18:45:45 UTC
2019 i686 i686 i686 GNU/Linux
Kernels 4.15.0-49 and prior work fine.
The kernel 4.18.0-20-generic works fine.
This problem has not been experienced with upstream Linux kernels.
It appears that invoking vmalloc_sync_all() a few times end up
triggering this issue. This can be triggered by restarting the lttng-
sessiond service with lttng-modules-dkms installed (sometimes a few
restarts are needed to trigger the bug). This ends up unloading and
reloading those modules, which issues a few vmalloc_sync_all() as side-
effect.
I'm not reporting this issue with the "ubuntu-bug linux" command because
it crashes the system on that kernel (system hangs, no console output).
My test system runs within a kvm virtual machine on a 64-bit host.
lsb release:
Description: Ubuntu 18.04.2 LTS
Release: 18.04
Information about my kernel:
linux-image-4.15.0-50-generic:
Installed: 4.15.0-50.54
Candidate: 4.15.0-50.54
Version table:
*** 4.15.0-50.54 500
500 http://ca.archive.ubuntu.com/ubuntu bionic-updates/main i386
Packages
500 http://security.ubuntu.com/ubuntu bionic-security/main i386 Packages
100 /var/lib/dpkg/status
Information about lttng-modules-dkms:
lttng-modules-dkms:
Installed: 2.10.5-1ubuntu1.2
Candidate: 2.10.5-1ubuntu1.2
Version table:
*** 2.10.5-1ubuntu1.2 500
500 http://ca.archive.ubuntu.com/ubuntu bionic-updates/universe i386
Packages
100 /var/lib/dpkg/status
2.10.5-1ubuntu1 500
500 http://ca.archive.ubuntu.com/ubuntu bionic/universe i386 Packages
** Affects: linux (Ubuntu)
Importance: Undecided
Status: Confirmed
** Tags: bionic
** Attachment added: "kernel BUG screenshot"
https://bugs.launchpad.net/bugs/1830433/+attachment/5266352/+files/Screenshot_ubuntu-bionic-32bit_2019-05-23_10%3A20%3A08.png
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https://bugs.launchpad.net/bugs/1830433
Title:
32-bit x86 kernel 4.15.0-50 crash in vmalloc_sync_all
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