We’re seeing it happen on both bare metal and virtual machines.
The VMs are libvirt/QEMU/KVM managed by OpenNebula. The hypervisor is
running AlmaLinux 8 with the 4.18.0-477.15.1.el8_8.x86_64 kernel. The
VMs have 2 physical/8 vCPUs allocated to them. The VM I used for the
reproduction has 2GB of R
Thank you for providing more information.
Unfortunately I am still unable to reproduce the problem. I tried using
a container and a VM, to no avail.
But I did open the coredump:
(gdb) bt
#0 _int_free (av=av@entry=0x7fcbaccd8b80 ,
p=p@entry=0x558afb81e0c0, have_lock=, have_lock@entry=1) at
ma
Yes, seems pretty consistent. I just tried it again before I write out
the reproduction steps, and it took maybe a couple of minutes.
The configuration is basically just:
sed -i.bak 's/#LogLevel INFO/LogLevel DEBUG/g' /etc/ssh/sshd_config
systemctl restart sshd
As for making enough connections t
Hi Ivaylo, thanks for all the information so far!
Can you consistently reproduce it?
Would you also mind sharing the exact steps it would take for us to
reproduce it from a fresh focal install?
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After some more "stress testing" with GNU parallel, I was able to
reproduce the segmentation fault, too. See attachment.
** Attachment added: "sshd segmentation fault crash report"
https://bugs.launchpad.net/ubuntu/+source/openssh/+bug/2043114/+attachment/5717935/+files/_usr_sbin_sshd.0.crash
Apologies for the multiple messages, but I was under the impression that
apport-collect would upload the actual core dump file here :)
** Attachment added: "sshd abort crash report"
https://bugs.launchpad.net/ubuntu/+source/openssh/+bug/2043114/+attachment/5717896/+files/_usr_sbin_sshd.0.crash
While trying to reproduce the segfault, I encountered another crash, an
abort in malloc this time. I cannot be absolutely sure, but it seems
that they might be related, so I am uploading the report now.
Edit: forgot to mention, it seems that the abort has also occurred on
the physical machine that
Thanks for getting back to me!
1. The crash seems to happen in a large percentage of the runs of a particular
test that does a lot of rapid SSH connections to the machine. Sadly, I don’t
have an exact number, but 50% probably wouldn’t be an exaggeration. It was also
happening in the setup part
Thank you Ivaylo for creating this bug report and helping make Ubuntu
better!
I have 2 follow up questions:
1. How often do these segmentation faults occur for you?
2. Have you tried to SSH to the Focal server from multiple other systems? Do
you encounter this issue with multiple systems, or is i
Status changed to 'Confirmed' because the bug affects multiple users.
** Changed in: openssh (Ubuntu)
Status: New => Confirmed
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