[Pkg-virtualbox-devel] Bug#838766: virtualbox-qt: segfault while deleting a snapshot on a VM with two virtual hard drives

[js]

Package: virtualbox-qt
Version: 5.1.6-dfsg-2+b1
Severity: important

Dear Maintainer,

I am using VirtualBox (from the Debian repositories) for virtualisation. One of
my VMs uses two virtual hard drives (Fixed-size VDIs of 120 GBytes each,
visible to the guest as SATA drives). I am trying to delete the oldest snapshot
on this VM, so the "original" (fixed-size) VDI files are to be modified as
changes are merged back into them from the oldest "difference" VDIs. Snapshot
deletion was triggered using the "delete snaphot" button in the QT GUI; the
host system was freshly booted, and no VMs were running.
VirtualBox merges the "difference" VDI back into the first fixed-size VDI. It
then deletes the "difference" VDI from the host filesystem, but instead of
working on the second virtual disk, the progress indicator just disappears. The
snapshot is still visible; the Virtual media Manager lists the "difference" VDI
that was just being deleted as "missing" (so obviously, the media registry was
not updated).
dmesg delivers the message "[  868.272600] DeleteSnap[2018]: segfault at 31 ip
000000000052bf8c sp 00007fb4b7b6d9c0 error 4 in VBoxSVC[400000+482000]" (the
precediung and following lines are not associated with VirtualBox). I have no
hints of physical media errors in the kernel log, so I consider the hard drive
as OK here.
htop shows that I am now having a total of three active VirtualBox processes,
which load two physical CPU cores at 100% each.

The expected behaviour would have been that nothing crashes, the VirtualBox
media registry is updated correctly, and the second virtual disk is processed
as well. Then, the configuration file for this VM shall be updated according to
the snapshot deletion, and the snapshot shall disappear from the snapshot tree.

I restored the VM from a backup and tried again, with the same result (however,
I did not check  dmesg and htop in the 2nd attempt).

The last time I deleted snapshots for this VM was with VirtualBox 5.0.24; I did
not have trouble there. VirtualBox 5.1.6 now shows the described behaviour.

I have no problems with deleting snapshots for VMs that have only one virtual
hard drive in VirtualBox 5.1.6, so this seems to be linked to the number of
virtual drives.



-- System Information:
Debian Release: stretch/sid
  APT prefers unstable
  APT policy: (500, 'unstable')
Architecture: amd64 (x86_64)
Foreign Architectures: i386

Kernel: Linux 4.7.0-1-amd64 (SMP w/4 CPU cores)
Locale: LANG=de_DE.UTF-8, LC_CTYPE=de_DE.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)

Versions of packages virtualbox-qt depends on:
ii  libc6                     2.24-3
ii  libgcc1                   1:6.2.0-4
ii  libgl1-mesa-glx [libgl1]  12.0.3-1
ii  libqt5core5a              5.6.1+dfsg-3+b1
ii  libqt5gui5                5.6.1+dfsg-3+b1
ii  libqt5opengl5             5.6.1+dfsg-3+b1
ii  libqt5printsupport5       5.6.1+dfsg-3+b1
ii  libqt5widgets5            5.6.1+dfsg-3+b1
ii  libqt5x11extras5          5.6.1-2
ii  libstdc++6                6.2.0-4
ii  libx11-6                  2:1.6.3-1
ii  libxcb1                   1.11.1-1.1
ii  libxext6                  2:1.3.3-1
ii  libxinerama1              2:1.1.3-1+b1
ii  virtualbox                5.1.6-dfsg-2+b1

virtualbox-qt recommends no packages.

virtualbox-qt suggests no packages.

-- no debconf information