This bug was fixed in the package linux - 4.15.0-50.54

---------------
linux (4.15.0-50.54) bionic; urgency=medium

  * CVE-2018-12126 // CVE-2018-12127 // CVE-2018-12130
    - Documentation/l1tf: Fix small spelling typo
    - x86/cpu: Sanitize FAM6_ATOM naming
    - kvm: x86: Report STIBP on GET_SUPPORTED_CPUID
    - locking/atomics, asm-generic: Move some macros from <linux/bitops.h> to a
      new <linux/bits.h> file
    - tools include: Adopt linux/bits.h
    - x86/msr-index: Cleanup bit defines
    - x86/speculation: Consolidate CPU whitelists
    - x86/speculation/mds: Add basic bug infrastructure for MDS
    - x86/speculation/mds: Add BUG_MSBDS_ONLY
    - x86/kvm: Expose X86_FEATURE_MD_CLEAR to guests
    - x86/speculation/mds: Add mds_clear_cpu_buffers()
    - x86/speculation/mds: Clear CPU buffers on exit to user
    - x86/kvm/vmx: Add MDS protection when L1D Flush is not active
    - x86/speculation/mds: Conditionally clear CPU buffers on idle entry
    - x86/speculation/mds: Add mitigation control for MDS
    - x86/speculation/mds: Add sysfs reporting for MDS
    - x86/speculation/mds: Add mitigation mode VMWERV
    - Documentation: Move L1TF to separate directory
    - Documentation: Add MDS vulnerability documentation
    - x86/speculation/mds: Add mds=full,nosmt cmdline option
    - x86/speculation: Move arch_smt_update() call to after mitigation decisions
    - x86/speculation/mds: Add SMT warning message
    - x86/speculation/mds: Fix comment
    - x86/speculation/mds: Print SMT vulnerable on MSBDS with mitigations off
    - x86/speculation/mds: Add 'mitigations=' support for MDS

  * CVE-2017-5715 // CVE-2017-5753
    - s390/speculation: Support 'mitigations=' cmdline option

  * CVE-2017-5715 // CVE-2017-5753 // CVE-2017-5754 // CVE-2018-3639
    - powerpc/speculation: Support 'mitigations=' cmdline option

  * CVE-2017-5715 // CVE-2017-5754 // CVE-2018-3620 // CVE-2018-3639 //
    CVE-2018-3646
    - cpu/speculation: Add 'mitigations=' cmdline option
    - x86/speculation: Support 'mitigations=' cmdline option

  * Packaging resync (LP: #1786013)
    - [Packaging] resync git-ubuntu-log

linux (4.15.0-49.53) bionic; urgency=medium

  * linux: 4.15.0-49.53 -proposed tracker (LP: #1826358)

  * Backport support for software count cache flush Spectre v2 mitigation. (CVE)
    (required for POWER9 DD2.3) (LP: #1822870)
    - powerpc/64s: Add support for ori barrier_nospec patching
    - powerpc/64s: Patch barrier_nospec in modules
    - powerpc/64s: Enable barrier_nospec based on firmware settings
    - powerpc: Use barrier_nospec in copy_from_user()
    - powerpc/64: Use barrier_nospec in syscall entry
    - powerpc/64s: Enhance the information in cpu_show_spectre_v1()
    - powerpc/64: Disable the speculation barrier from the command line
    - powerpc/64: Make stf barrier PPC_BOOK3S_64 specific.
    - powerpc/64: Add CONFIG_PPC_BARRIER_NOSPEC
    - powerpc/64: Call setup_barrier_nospec() from setup_arch()
    - powerpc/64: Make meltdown reporting Book3S 64 specific
    - powerpc/lib/code-patching: refactor patch_instruction()
    - powerpc/lib/feature-fixups: use raw_patch_instruction()
    - powerpc/asm: Add a patch_site macro & helpers for patching instructions
    - powerpc/64s: Add new security feature flags for count cache flush
    - powerpc/64s: Add support for software count cache flush
    - powerpc/pseries: Query hypervisor for count cache flush settings
    - powerpc/powernv: Query firmware for count cache flush settings
    - powerpc/fsl: Add nospectre_v2 command line argument
    - KVM: PPC: Book3S: Add count cache flush parameters to 
kvmppc_get_cpu_char()
    - [Config] Add CONFIG_PPC_BARRIER_NOSPEC

  * Packaging resync (LP: #1786013)
    - [Packaging] resync git-ubuntu-log

  * autopkgtests run too often, too much and don't skip enough (LP: #1823056)
    - [Debian] Set +x on rebuild testcase.
    - [Debian] Skip rebuild test, for regression-suite deps.
    - [Debian] Make ubuntu-regression-suite skippable on unbootable kernels.
    - [Debian] make rebuild use skippable error codes when skipping.
    - [Debian] Only run regression-suite, if requested to.

  * bionic: fork out linux-snapdragon into its own topic kernel (LP: #1820868)
    - [Packaging] remove arm64 snapdragon from getabis
    - [Config] config changes for snapdragon split
    - packaging: arm64: disable building the snapdragon flavour
    - [Packaging] arm64: Drop snapdragon from kernel-versions

  * CVE-2017-5753
    - KVM: arm/arm64: vgic: fix possible spectre-v1 in vgic_get_irq()
    - media: dvb_ca_en50221: prevent using slot_info for Spectre attacs
    - sysvipc/sem: mitigate semnum index against spectre v1
    - libahci: Fix possible Spectre-v1 pmp indexing in ahci_led_store()
    - s390/keyboard: sanitize array index in do_kdsk_ioctl
    - arm64: fix possible spectre-v1 write in ptrace_hbp_set_event()
    - KVM: arm/arm64: vgic: Fix possible spectre-v1 write in 
vgic_mmio_write_apr()
    - pktcdvd: Fix possible Spectre-v1 for pkt_devs
    - net: socket: fix potential spectre v1 gadget in socketcall
    - net: socket: Fix potential spectre v1 gadget in sock_is_registered
    - drm/amdgpu/pm: Fix potential Spectre v1
    - netlink: Fix spectre v1 gadget in netlink_create()
    - ext4: fix spectre gadget in ext4_mb_regular_allocator()
    - drm/i915/kvmgt: Fix potential Spectre v1
    - net: sock_diag: Fix spectre v1 gadget in __sock_diag_cmd()
    - fs/quota: Fix spectre gadget in do_quotactl
    - hwmon: (nct6775) Fix potential Spectre v1
    - mac80211_hwsim: Fix possible Spectre-v1 for hwsim_world_regdom_custom
    - switchtec: Fix Spectre v1 vulnerability
    - misc: hmc6352: fix potential Spectre v1
    - tty: vt_ioctl: fix potential Spectre v1
    - nl80211: Fix possible Spectre-v1 for NL80211_TXRATE_HT
    - nl80211: Fix possible Spectre-v1 for CQM RSSI thresholds
    - IB/ucm: Fix Spectre v1 vulnerability
    - RDMA/ucma: Fix Spectre v1 vulnerability
    - drm/bufs: Fix Spectre v1 vulnerability
    - usb: gadget: storage: Fix Spectre v1 vulnerability
    - ptp: fix Spectre v1 vulnerability
    - HID: hiddev: fix potential Spectre v1
    - vhost: Fix Spectre V1 vulnerability
    - drivers/misc/sgi-gru: fix Spectre v1 vulnerability
    - ipv4: Fix potential Spectre v1 vulnerability
    - aio: fix spectre gadget in lookup_ioctx
    - ALSA: emux: Fix potential Spectre v1 vulnerabilities
    - ALSA: pcm: Fix potential Spectre v1 vulnerability
    - ip6mr: Fix potential Spectre v1 vulnerability
    - ALSA: rme9652: Fix potential Spectre v1 vulnerability
    - ALSA: emu10k1: Fix potential Spectre v1 vulnerabilities
    - KVM: arm/arm64: vgic: Fix off-by-one bug in vgic_get_irq()
    - drm/ioctl: Fix Spectre v1 vulnerabilities
    - char/mwave: fix potential Spectre v1 vulnerability
    - applicom: Fix potential Spectre v1 vulnerabilities
    - ipmi: msghandler: Fix potential Spectre v1 vulnerabilities
    - powerpc/ptrace: Mitigate potential Spectre v1
    - cfg80211: prevent speculation on cfg80211_classify8021d() return
    - ALSA: rawmidi: Fix potential Spectre v1 vulnerability
    - ALSA: seq: oss: Fix Spectre v1 vulnerability

  * Bionic: Sync to Xenial (Spectre) (LP: #1822760)
    - x86/speculation/l1tf: Suggest what to do on systems with too much RAM
    - KVM: SVM: Add MSR-based feature support for serializing LFENCE
    - KVM: VMX: fixes for vmentry_l1d_flush module parameter
    - KVM: X86: Allow userspace to define the microcode version
    - SAUCE: [Fix] x86/KVM/VMX: Add L1D flush logic
    - SAUCE: [Fix] x86/speculation: Use ARCH_CAPABILITIES to skip L1D flush on
      vmentry

  * [SRU] [B/OEM] Fix ACPI bug that causes boot failure (LP: #1819921)
    - SAUCE: ACPI / bus: Add some Lenovo laptops in list of acpi table term list

  * Bionic update: upstream stable patchset for fuse 2019-04-12 (LP: #1824553)
    - fuse: fix double request_end()
    - fuse: fix unlocked access to processing queue
    - fuse: umount should wait for all requests
    - fuse: Fix oops at process_init_reply()
    - fuse: Don't access pipe->buffers without pipe_lock()
    - fuse: Fix use-after-free in fuse_dev_do_read()
    - fuse: Fix use-after-free in fuse_dev_do_write()
    - fuse: set FR_SENT while locked
    - fuse: fix blocked_waitq wakeup
    - fuse: fix leaked notify reply
    - fuse: fix possibly missed wake-up after abort
    - fuse: fix use-after-free in fuse_direct_IO()
    - fuse: continue to send FUSE_RELEASEDIR when FUSE_OPEN returns ENOSYS
    - fuse: handle zero sized retrieve correctly
    - fuse: call pipe_buf_release() under pipe lock
    - fuse: decrement NR_WRITEBACK_TEMP on the right page

  * Backport support for software count cache flush Spectre v2 mitigation. (CVE)
    (required for POWER9 DD2.3) (LP: #1822870) // Backport support for software
    count cache flush Spectre v2 mitigation. (CVE) (required for POWER9 DD2.3)
    (LP: #1822870)
    - powerpc64s: Show ori31 availability in spectre_v1 sysfs file not v2
    - powerpc/fsl: Fix spectre_v2 mitigations reporting
    - powerpc: Avoid code patching freed init sections

  * Backport support for software count cache flush Spectre v2 mitigation. (CVE)
    (required for POWER9 DD2.3) (LP: #1822870) // Backport support for software
    count cache flush Spectre v2 mitigation. (CVE) (required for POWER9 DD2.3)
    (LP: #1822870) // Backport support for software count cache flush Spectre v2
    mitigation. (CVE) (required for POWER9 DD2.3) (LP: #1822870)
    - powerpc/security: Fix spectre_v2 reporting

  * CVE-2019-3874
    - sctp: use sk_wmem_queued to check for writable space
    - sctp: implement memory accounting on tx path
    - sctp: implement memory accounting on rx path

  * NULL pointer dereference when using z3fold and zswap (LP: #1814874)
    - z3fold: fix possible reclaim races

  * Kprobe event argument syntax in ftrace from ubuntu_kernel_selftests failed
    on B PowerPC (LP: #1812809)
    - selftests/ftrace: Add ppc support for kprobe args tests

  * The Realtek card reader does not enter PCIe 1.1/1.2 (LP: #1825487)
    - misc: rtsx: make various functions static
    - misc: rtsx: Enable OCP for rts522a rts524a rts525a rts5260
    - SAUCE: misc: rtsx: Fixed rts5260 power saving parameter and sd glitch

  * headset-mic doesn't work on two Dell laptops. (LP: #1825272)
    - ALSA: hda/realtek - add two more pin configuration sets to quirk table

  * CVE-2018-16884
    - sunrpc: use SVC_NET() in svcauth_gss_* functions
    - sunrpc: use-after-free in svc_process_common()

  * sky2 ethernet card don't work after returning from suspension (LP: #1798921)
    - sky2: Increase D3 delay again

  * CVE-2019-9500
    - brcmfmac: assure SSID length from firmware is limited

  * CVE-2019-9503
    - brcmfmac: add subtype check for event handling in data path

  * CVE-2019-3882
    - vfio/type1: Limit DMA mappings per container

  * Intel I210 Ethernet card not working after hotplug [8086:1533]
    (LP: #1818490)
    - igb: Fix WARN_ONCE on runtime suspend

  * bionic, xenial/hwe: misses "fuse: fix initial parallel dirops" patch
    (LP: #1823972)
    - fuse: fix initial parallel dirops

  * amdgpu resume failure: failed to allocate wb slot (LP: #1825074)
    - drm/amdgpu: fix&cleanups for wb_clear

  * Pop noise when headset is plugged in or removed from GHS/Line-out jack
    (LP: #1821290)
    - ALSA: hda/realtek - Add unplug function into unplug state of Headset Mode
      for ALC225
    - ALSA: hda/realtek - Disable headset Mic VREF for headset mode of ALC225
    - ALSA: hda/realtek - Add support headset mode for DELL WYSE AIO
    - ALSA: hda/realtek - Add support headset mode for New DELL WYSE NB

  * mac80211_hwsim unable to handle kernel NULL pointer dereference
    at0000000000000000  (LP: #1825058)
    - mac80211_hwsim: Timer should be initialized before device registered

  * [regression][snd_hda_codec_realtek] repeating crackling noise after 19.04
    upgrade (LP: #1821663)
    - ALSA: hda: Add Intel NUC7i3BNB to the power_save blacklist
    - ALSA: hda - add Lenovo IdeaCentre B550 to the power_save_blacklist
    - ALSA: hda - Add two more machines to the power_save_blacklist

  * ubuntu_nbd_smoke_test failed on P9 with Bionic kernel (LP: #1822247)
    - nbd: fix how we set bd_invalidated

  * TSC clocksource not available in nested guests (LP: #1822821)
    - kvmclock: fix TSC calibration for nested guests

  * 4.15 kernel ip_vs --ops causes performance and hang problem (LP: #1819786)
    - ipvs: fix refcount usage for conns in ops mode

  * systemd cause kernel trace "BUG: unable to handle kernel paging request at
    6db23a14" on Cosmic i386 (LP: #1813244) // systemd cause kernel trace "BUG:
    unable to handle kernel paging request at 6db23a14" on Cosmic i386
    (LP: #1813244)
    - openvswitch: fix flow actions reallocation

 -- Stefan Bader <stefan.ba...@canonical.com>  Mon, 06 May 2019 18:59:24
+0200

** Changed in: linux (Ubuntu Bionic)
       Status: Fix Committed => Fix Released

** CVE added: https://cve.mitre.org/cgi-bin/cvename.cgi?name=2017-5715

** CVE added: https://cve.mitre.org/cgi-bin/cvename.cgi?name=2017-5753

** CVE added: https://cve.mitre.org/cgi-bin/cvename.cgi?name=2017-5754

** CVE added: https://cve.mitre.org/cgi-bin/cvename.cgi?name=2018-12126

** CVE added: https://cve.mitre.org/cgi-bin/cvename.cgi?name=2018-12127

** CVE added: https://cve.mitre.org/cgi-bin/cvename.cgi?name=2018-12130

** CVE added: https://cve.mitre.org/cgi-bin/cvename.cgi?name=2018-16884

** CVE added: https://cve.mitre.org/cgi-bin/cvename.cgi?name=2018-3620

** CVE added: https://cve.mitre.org/cgi-bin/cvename.cgi?name=2018-3639

** CVE added: https://cve.mitre.org/cgi-bin/cvename.cgi?name=2018-3646

** CVE added: https://cve.mitre.org/cgi-bin/cvename.cgi?name=2019-3874

** CVE added: https://cve.mitre.org/cgi-bin/cvename.cgi?name=2019-3882

** CVE added: https://cve.mitre.org/cgi-bin/cvename.cgi?name=2019-9500

** CVE added: https://cve.mitre.org/cgi-bin/cvename.cgi?name=2019-9503

** Changed in: linux (Ubuntu Cosmic)
       Status: Fix Committed => Fix Released

** CVE added: https://cve.mitre.org/cgi-bin/cvename.cgi?name=2019-3887

-- 
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https://bugs.launchpad.net/bugs/1814874

Title:
  NULL pointer dereference when using z3fold and zswap

Status in Linux:
  Fix Released
Status in linux package in Ubuntu:
  Fix Released
Status in linux source package in Bionic:
  Fix Released
Status in linux source package in Cosmic:
  Fix Released

Bug description:
  == Justification ==
  When using z3fold and zswap on a VM under overcommitted memory stress,
  z3fold will complains about an "unknown buddy id 0" and fail to get a
  pointer to the mapped allocation in z3fold_map().

   z3fold: unknown buddy id 0
   WARNING: CPU: 2 PID: 1584 at mm/z3fold.c:971 z3fold_zpool_map+0xce/0x100 
[z3fold]

  And it will leads to a null pointer dereference in zswap

   BUG: unable to handle kernel NULL pointer dereference at 0000000000000000
   PGD 0 P4D 0
   Oops: 0000 [#1] SMP PTI
   CPU: 2 PID: 1584 Comm: stress Tainted: G        W         4.18.0-17-generic 
#18-Ubuntu
   Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.11.1-1ubuntu1 
04/01/2014
   RIP: 0010:zswap_writeback_entry+0x4d/0x360

  == Fix ==
  ca0246bb (z3fold: fix possible reclaim races)

  This patch has already in Disco, and can be cherry-picked into B/C.
  Not needed for Xenial and older kernels as z3fold is not supported.

  == Test ==
  Test kernels for Bionic / Cosmic could be found here:
  http://people.canonical.com/~phlin/kernel/lp-1814874-z3fold-zswap/Bionic/
  http://people.canonical.com/~phlin/kernel/lp-1814874-z3fold-zswap/Cosmic/

  This issue can be reproduced easily in a KVM with the following setup:
   * 8G disk, 4G RAM, 4 CPUs
   * 1G swap
   * "zswap.enabled=1 zswap.zpool=z3fold zswap.max_pool_percent=7" added to grub
   * "z3fold" module added into /etc/initramfs-tools/modules

  Stress it with two childs running:
   * stress --vm-bytes 512M --vm 4 --vm-hang 3
   * stress --vm-bytes 512M --vm 4 --vm-hang 7

  The VM is expected to crash within 5 minutes.

  With the patched kernel, the VM can withstand this stress for over an
  hour with crashing with this issue

  == Regression potential ==
  Small.

  Fix limited to z3fold. User needs to enable it explicitly for this
  feature.

  
  == Original Bug Report ==
  Under memory pressure, my VM locks up. This has been reported upstream though 
I don't know how far any solution has progressed.

  https://bugzilla.kernel.org/show_bug.cgi?id=201603

  Feb  6 07:15:42 vps632258 kernel: [151336.450064] z3fold: unknown buddy id 0
  Feb  6 07:15:42 vps632258 kernel: [151336.454450] BUG: unable to handle 
kernel NULL pointer dereference at 0000000000000008

  The little bit of log I managed to salvage is attached.

  This has happened to two identical VMs. Unusually it has not occurred
  on a third VM which is configured the same but has less RAM (fingers
  crossed it won't).

  Irrelevant information:
  I thought the lock-ups were due to me using a BTRFS filesystem, however I 
swapped over to NILFS2 and this still occurs. The only difference seems to be 
that I am now able to grab some of the kernel output.

  ProblemType: Bug
  DistroRelease: Ubuntu 18.04
  Package: linux-image-4.18.0-14-generic 4.18.0-14.15~18.04.1
  ProcVersionSignature: Ubuntu 4.18.0-14.15~18.04.1-generic 4.18.20
  Uname: Linux 4.18.0-14-generic x86_64
  ApportVersion: 2.20.9-0ubuntu7.5
  Architecture: amd64
  Date: Wed Feb  6 10:55:05 2019
  ProcEnviron:
   TERM=xterm
   PATH=(custom, no user)
   XDG_RUNTIME_DIR=<set>
   LANG=en_GB.UTF-8
   SHELL=/bin/bash
  SourcePackage: linux-signed-hwe
  UpgradeStatus: No upgrade log present (probably fresh install)

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