[Bug 1844455] Re: Memory leak of struct _virPCIDeviceAddress on libvirt

[Robie Basak]

Hello Guilherme, or anyone else affected,

Accepted libvirt into xenial-proposed. The package will build now and be
available at
https://launchpad.net/ubuntu/+source/libvirt/1.3.1-1ubuntu10.30 in a few
hours, and then in the -proposed repository.

Please help us by testing this new package.  See
https://wiki.ubuntu.com/Testing/EnableProposed for documentation on how
to enable and use -proposed.  Your feedback will aid us getting this
update out to other Ubuntu users.

If this package fixes the bug for you, please add a comment to this bug,
mentioning the version of the package you tested and change the tag from
verification-needed-xenial to verification-done-xenial. If it does not
fix the bug for you, please add a comment stating that, and change the
tag to verification-failed-xenial. In either case, without details of
your testing we will not be able to proceed.

Further information regarding the verification process can be found at
https://wiki.ubuntu.com/QATeam/PerformingSRUVerification .  Thank you in
advance for helping!

N.B. The updated package will be released to -updates after the bug(s)
fixed by this package have been verified and the package has been in
-proposed for a minimum of 7 days.

** Changed in: libvirt (Ubuntu Xenial)
       Status: In Progress => Fix Committed

** Tags added: verification-needed-xenial

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https://bugs.launchpad.net/bugs/1844455

Title:
  Memory leak of struct _virPCIDeviceAddress on libvirt

Status in Ubuntu Cloud Archive:
  Confirmed
Status in Ubuntu Cloud Archive mitaka series:
  Confirmed
Status in libvirt package in Ubuntu:
  Fix Released
Status in libvirt source package in Xenial:
  Fix Committed
Status in libvirt source package in Bionic:
  Fix Committed
Status in libvirt source package in Eoan:
  Fix Committed
Status in libvirt source package in Focal:
  Fix Released

Bug description:
  [Impact]
  * There's a long-term memory leak in libvirt related to the PCI information gathering from sysfs in Linux, specially related with SR-IOV devices. This was fixed by commit 38816336 ("node_device_conf: Don't leak @physical_function in virNodeDeviceGetPCISRIOVCaps") [ libvirt.org/git/?p=libvirt.git;a=commit;h=38816336 ].

  * In comment #9 there is a detailed explanation of what's going on,
  but the summary is that the variable physical_function (member of a
  PCI structure), of type _virPCIDeviceAddress, is allocated on
  virPCIGetDeviceAddressFromSysfsLink() and should be freed before reuse
  in virNodeDeviceGetPCISRIOVCaps(), but it wasn't before the fix was
  introduced.

  * The impact of the issue is a memory leak usually small but that may
  grow bigger depending on the amount of PCI devices and how/when they
  are enumerated by libvirt; if some user of those functions are
  actively exercising the leak path it may become a problem (OOM
  situation).

  [Test Case]
  * The basic testing done to exercise the memory leak path was running the virsh tool to generate the XML output of a SR-IOV PCI device in a loop, like:

  while true; do virsh nodedev-dumpxml pci_0000_08_12_0 >/dev/null; done

  * This was executed while Valgrind was used to debug libvirtd, in
  order to collect the signature of the leak. Without the patch we get
  the "definitely lost" type of leak with the PCI backtrace (on comment
  #9), whereas with the patch we don't see the leak anymore.

  [Regression Potential]
  * The potential of regressions is really low - the fix is upstream for a while and in Focal package, and it is self-contained and not intrusive. Considering hypothetical scenarios, if there's an issue with the fix it should come in form of unused memory or double-free (which is usually harmless), and only in PCI enumeration (or PCI XML generation) paths.

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