[Bug 1877089] Re: zfcpdump kernel can not be IPLed when secure boot is requested

[Dimitri John Ledkov]

Hm, I'm not sure we can sign the zfcpdump-kernel.

By convention, in Focal, signed kernels enforce signed module loading &
lockdown that prevents unsigned module loading, kexec unsigned kernels
or reading arbitrary kernel memory from userspace. And I am under
impression that zfcpdump kernel/initrd rely on being able to read kernel
memory.

The zfcpdump-kernel flavour currently is built using zfcpdump_defconfig.
I would be more comfortable if we could use the stock signed kernel
image as the zfcpdump one, instead of the purpose built one. And include
any missing modules in the zfcpdump initrd and/or adjust the cmdline to
do things like PANIC_ON_OOPS=y. But i guess we will not get
CONFIG_CC_OPTIMIZE_FOR_SIZE=y with the stock kernel image.

Does zfcdump work with locked-down kernels?
Why do we want/prefer a separate kernel flavour for zfcpdump, instead of the stock one?

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Title:
  zfcpdump kernel can not be IPLed when secure boot is requested

Status in Ubuntu on IBM z Systems:
  Triaged
Status in s390-tools package in Ubuntu:
  Invalid
Status in zfcpdump-kernel package in Ubuntu:
  Confirmed
Status in zfcpdump-kernel source package in Focal:
  Confirmed
Status in zfcpdump-kernel source package in Groovy:
  Confirmed

Bug description:
  I installed Ubuntu 20.04 on IBM z15 with secure=1 in zipl conf.
  System can be secure booted, /sys/firmware/ipl/secure shows "1".
  I prepared zfcp dump disk as described in LTC bug 185713.
  Stopped the system and performed a SCSI dump with "Enable Secure Boot for Linux" enabled.

  Operating System Messages on HMC:
  Preparing system.
  Starting system.
  System version 8.
  Watchdog enabled.
  Running 'ZBootLoader' version '1.0.0' level 'D41C.D41C_0014'.
  ZBootLoader 2.1.0.
  MLOLOA6269064E Secure IPL: There are no signed components available on device HB
  A=0.0.1800, WWPN=500507630309D327, LUN=4046400900000000.
  IPL failed.

  Without "Enable Secure Boot for Linux" the dump kernel was IPLed and a
  dump created.

  Then I tried to rewrite the zfcp dump kernel with explicite setting of --secure=1:
  root at t35lp25:~# zipl --secure=1 -d /dev/disk/by-id/scsi-36005076303ffd3270000000000004609-part1
  Building bootmap directly on partition '/dev/disk/by-id/scsi-36005076303ffd3270000000000004609-part1'
  Adding dump section
    initial ramdisk...: /lib/s390-tools/zfcpdump/zfcpdump-initrd
    kernel image......: /lib/s390-tools/zfcpdump/zfcpdump-image
    kernel parmline...: 'root=/dev/ram0 dump_mem=1 possible_cpus=1 cgroup_disable=memory '
    component address:
      heap area.......: 0x00002000-0x00005fff
      stack area......: 0x0000f000-0x0000ffff
      internal loader.: 0x0000a000-0x0000dfff
      parameters......: 0x00009000-0x000091ff
      kernel image....: 0x00010000-0x001b9fff
      parmline........: 0x001ba000-0x001ba1ff
      initial ramdisk.: 0x001c0000-0x0020edff
  Preparing boot device: sde.
  Done.

  ...and tried to SCSI dump this device again. But the same  failure occured.
  Again, without "Enable Secure Boot for Linux" the dump kernel was IPLed and a dump created.

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