** Changed in: linux (Ubuntu Focal)
       Status: In Progress => Fix Committed

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https://bugs.launchpad.net/bugs/1874057

Title:
  [UBUNTU 20.04] s390x/pci: do not allow to create more pci functions
  than configured via CONFIG_PCI_NR_FUNCTIONS

Status in Ubuntu on IBM z Systems:
  In Progress
Status in linux package in Ubuntu:
  In Progress
Status in linux source package in Focal:
  Fix Committed
Status in linux source package in Groovy:
  In Progress

Bug description:
  SRU Justification:
  ==================

  [Impact]

  * PCI Functions with UIDs >128 are currently not accounted correctly
  in the s390x/pci (zPCI) code.

  * Furthermore, the code allows that more than CONFIG_PCI_NR_FUNCTIONS
  are created.

  * This can lead to issues with data structures which were only
  allocated for CONFIG_PCI_NR_FUNCTIONS.

  [Fix]

  * https://launchpadlibrarian.net/478235080/0001-s390-pci-Fix-
  zpci_alloc_domain-over-allocation.patch

  [Test Case]

  * Set the kernel parameter CONFIG_PCI_NR_FUNCTIONS to a specific
  (reasonablly low) number.

  * And check if more PCI functions can be created than specified by
  CONFIG_PCI_NR_FUNCTIONS (e.g. using a RoCE adapter) and watch for
  kernel message 'Adding PCI function ... failed'

  [Regression Potential]

  * There is regression potential can be considered as low, since:

  * the zPCI cards are less wide spread than for example ccw adapters on
  s390x

  * the fix got already upstream accepted in 5.7, hence upstream
  reviewed, too

  * the modifications span just two files and both are s390x arch
  specific

  [Other Info]

  * the above patch-file is based on commit
  969ae01bab2fe938b4c8324836038b5ac1c78fac ("s390/pci: Fix
  zpci_alloc_domain() over allocation"), but this backport was needed
  for getting this applied to focal master-next

  * and this patch got upstream accepted with kernel v5.7-rc1, hence on
  the long term it should be in 'gorilla'

  __________

  PCI Functions with UIDs >128 are currently not accounted correctly in
  the s390x/pci code. Furthermore, the code allows that more than
  CONFIG_PCI_NR_FUNCTIONS are created. This can lead to issues with data
  structures which were only allocated for CONFIG_PCI_NR_FUNCTIONS.

  This has been fixed in the following upstream commit:

  969ae01bab2fe938b4c8324836038b5ac1c78fac
  ("s390/pci: Fix zpci_alloc_domain() over allocation")

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