This bug was fixed in the package linux - 4.15.0-39.42

---------------
linux (4.15.0-39.42) bionic; urgency=medium

  * linux: 4.15.0-39.42 -proposed tracker (LP: #1799411)

  * Linux: insufficient shootdown for paging-structure caches (LP: #1798897)
    - mm: move tlb_table_flush to tlb_flush_mmu_free
    - mm/tlb: Remove tlb_remove_table() non-concurrent condition
    - mm/tlb, x86/mm: Support invalidating TLB caches for RCU_TABLE_FREE
    - [Config] CONFIG_HAVE_RCU_TABLE_INVALIDATE=y

  * Ubuntu18.04: GPU total memory is reduced (LP: #1792102)
    - Revert "powerpc/powernv: Increase memory block size to 1GB on radix"

  * arm64: snapdragon: reduce boot noise (LP: #1797154)
    - [Config] arm64: snapdragon: DRM_MSM=m
    - [Config] arm64: snapdragon: SND*=m
    - [Config] arm64: snapdragon: disable ARM_SDE_INTERFACE
    - [Config] arm64: snapdragon: disable DRM_I2C_ADV7511_CEC
    - [Config] arm64: snapdragon: disable VIDEO_ADV7511, VIDEO_COBALT

  * [Bionic] CPPC bug fixes (LP: #1796949)
    - ACPI / CPPC: Update all pr_(debug/err) messages to log the susbspace id
    - cpufreq: CPPC: Don't set transition_latency
    - ACPI / CPPC: Fix invalid PCC channel status errors

  * regression in 'ip --family bridge neigh' since linux v4.12 (LP: #1796748)
    - rtnetlink: fix rtnl_fdb_dump() for ndmsg header

  * screen displays abnormally on the lenovo M715 with the AMD GPU (Radeon Vega
    8 Mobile, rev ca, 1002:15dd) (LP: #1796786)
    - drm/amd/display: Fix takover from VGA mode
    - drm/amd/display: early return if not in vga mode in disable_vga
    - drm/amd/display: Refine disable VGA

  * arm64: snapdragon: WARNING: CPU: 0 PID: 1 arch/arm64/kernel/setup.c:271
    reserve_memblock_reserved_regions (LP: #1797139)
    - SAUCE: arm64: Fix /proc/iomem for reserved but not memory regions

  * The front MIC can't work on the Lenovo M715 (LP: #1797292)
    - ALSA: hda/realtek - Fix the problem of the front MIC on the Lenovo M715

  * Keyboard backlight sysfs sometimes is missing on Dell laptops (LP: #1797304)
    - platform/x86: dell-smbios: Correct some style warnings
    - platform/x86: dell-smbios: Rename dell-smbios source to dell-smbios-base
    - platform/x86: dell-smbios: Link all dell-smbios-* modules together
    - [Config] CONFIG_DELL_SMBIOS_SMM=y, CONFIG_DELL_SMBIOS_WMI=y

  * rpi3b+: ethernet not working (LP: #1797406)
    - lan78xx: Don't reset the interface on open

  * 87cdf3148b11 was never backported to 4.15  (LP: #1795653)
    - xfrm: Verify MAC header exists before overwriting eth_hdr(skb)->h_proto

  * [Ubuntu18.04][Power9][DD2.2]package installation segfaults inside debian
    chroot env in P9 KVM guest with HTM enabled (kvm) (LP: #1792501)
    - KVM: PPC: Book3S HV: Fix guest r11 corruption with POWER9 TM workarounds

  * Provide mode where all vCPUs on a core must be the same VM (LP: #1792957)
    - KVM: PPC: Book3S HV: Provide mode where all vCPUs on a core must be the 
same
      VM

  * fscache: bad refcounting in fscache_op_complete leads to OOPS (LP: #1797314)
    - SAUCE: fscache: Fix race in decrementing refcount of op->npages

  * CVE-2018-9363
    - Bluetooth: hidp: buffer overflow in hidp_process_report

  * CVE-2017-13168
    - scsi: sg: mitigate read/write abuse

  * [Bionic] ACPI / PPTT: use ACPI ID whenever ACPI_PPTT_ACPI_PROCESSOR_ID_VALID
    is set (LP: #1797200)
    - ACPI / PPTT: use ACPI ID whenever ACPI_PPTT_ACPI_PROCESSOR_ID_VALID is set

  * [Bionic] arm64: topology: Avoid checking numa mask for scheduler MC
    selection (LP: #1797202)
    - arm64: topology: Avoid checking numa mask for scheduler MC selection

  * crypto/vmx - Backport of Fix sleep-in-atomic bugs patch for 18.04
    (LP: #1790832)
    - crypto: vmx - Fix sleep-in-atomic bugs

  * hns3: autoneg settings get lost on down/up (LP: #1797654)
    - net: hns3: Fix for information of phydev lost problem when down/up

  * not able to unwind the stack from within __kernel_clock_gettime in the Linux
    vDSO (LP: #1797963)
    - powerpc/vdso: Correct call frame information

  * Signal 7 error when running GPFS tracing in cluster (LP: #1792195)
    - powerpc/mm/books3s: Add new pte bit to mark pte temporarily invalid.
    - powerpc/mm/radix: Only need the Nest MMU workaround for R -> RW transition

  * Support Edge Gateway's WIFI LED (LP: #1798330)
    - SAUCE: mwifiex: Switch WiFi LED state according to the device status

  * Support Edge Gateway's Bluetooth LED (LP: #1798332)
    - SAUCE: Bluetooth: Support for LED on Edge Gateways

  * USB cardreader (0bda:0328) make the system can't enter s3 or hang
    (LP: #1798328)
    - usb: Don't disable Latency tolerance Messaging (LTM) before port reset

  * CVE-2018-15471
    - xen-netback: fix input validation in xenvif_set_hash_mapping()

  * CVE-2018-16658
    - cdrom: Fix info leak/OOB read in cdrom_ioctl_drive_status

  * [Bionic] Update ThunderX2 implementation defined pmu core events
    (LP: #1796904)
    - perf vendor events arm64: Update ThunderX2 implementation defined pmu core
      events

  * the machine of lenovo M715 with the AMD GPU (Radeon Vega 8 Mobile, rev ca,
    1002:15dd) often hangs randomly (LP: #1796789)
    - drm/amd: Add missing fields in atom_integrated_system_info_v1_11

  * [18.04] GLK hang after a while (LP: #1760545)
    - drm/i915/glk: Add MODULE_FIRMWARE for Geminilake

  * Fix usbcore.quirks when used at boot (LP: #1795784)
    - usb: core: safely deal with the dynamic quirk lists

 -- Kleber Sacilotto de Souza <kleber.so...@canonical.com>  Tue, 23 Oct
2018 14:44:55 +0000

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

** CVE added: https://cve.mitre.org/cgi-bin/cvename.cgi?name=2017-13168

** CVE added: https://cve.mitre.org/cgi-bin/cvename.cgi?name=2018-15471

** CVE added: https://cve.mitre.org/cgi-bin/cvename.cgi?name=2018-16658

** CVE added: https://cve.mitre.org/cgi-bin/cvename.cgi?name=2018-9363

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https://bugs.launchpad.net/bugs/1797963

Title:
  not able to unwind the stack from within __kernel_clock_gettime in the
  Linux vDSO

Status in The Ubuntu-power-systems project:
  Fix Committed
Status in linux package in Ubuntu:
  Fix Committed
Status in linux source package in Bionic:
  Fix Released
Status in linux source package in Cosmic:
  Fix Committed

Bug description:
  == SRU Justification ==
  IBM is requesting this commit in Bionic and Cosmic.  They report that they
  are not able to unwind the stack from within __kernel_clock_gettime in the
  Linux vDSO on Summit. This affects both DDT and MAP (via GDB and libunwind).
  The issue is more serious than may first appear as the function appears to
  be called somewhat often by the CUDA runtime, and can defer to a syscall
  making it relatively time consuming (making it more likely to be encountered).

  This commit is currently still in linux-next.

  == Fix ==
  56d20861c027 ("powerpc/vdso: Correct call frame information") linux-next

  == Regression Potential ==
  Low.  Limited to powerpc.





  
  Original Bug Description

  We're not able to unwind the stack from within __kernel_clock_gettime
  in the Linux vDSO on Summit. This affects both DDT and MAP (via GDB
  and libunwind). The issue is more serious than may first appear as the
  function appears to be called somewhat often by the CUDA runtime, and
  can defer to a syscall making it relatively time consuming (making it
  more likely to be encountered).

  To reproduce:

  Compile $CUDA_DIR/samples/0_Simple/matrixMul (attached is a small
  patch to modify the Makefile to compile outside of the samples
  directory)

  Run the following GDB commands:
  user@deb3qwsp1:/usr/local/cuda-10.0/samples/0_Simple/matrixMul$ gdb 
./matrixMul
  GNU gdb (Ubuntu 8.1-0ubuntu3) 8.1.0.20180409-git
  Copyright (C) 2018 Free Software Foundation, Inc.
  License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
  This is free software: you are free to change and redistribute it.
  There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
  and "show warranty" for details.
  This GDB was configured as "powerpc64le-linux-gnu".
  Type "show configuration" for configuration details.
  For bug reporting instructions, please see:
  <http://www.gnu.org/software/gdb/bugs/>.
  Find the GDB manual and other documentation resources online at:
  <http://www.gnu.org/software/gdb/documentation/>.
  For help, type "help".
  Type "apropos word" to search for commands related to "word"...
  Reading symbols from ./matrixMul...(no debugging symbols found)...done.
  (gdb) break main
  Breakpoint 1 at 0x8284
  (gdb) run
  Starting program: /usr/local/cuda-10.0/samples/0_Simple/matrixMul/matrixMul
  [Thread debugging using libthread_db enabled]
  Using host libthread_db library 
"/lib/powerpc64le-linux-gnu/libthread_db.so.1".

  Breakpoint 1, 0x0000000100008284 in main ()
  (gdb) break *(__kernel_clock_gettime+144)
  Breakpoint 2 at 0x7ffff7f805e4: file 
/build/linux-ZIBxfV/linux-4.15.0/arch/powerpc/kernel/vdso64/gettimeofday.S, 
line 127.
  (gdb) continue
  Continuing.
  [Matrix Multiply Using CUDA] - Starting...

  Breakpoint 2, __kernel_clock_gettime () at 
/build/linux-ZIBxfV/linux-4.15.0/arch/powerpc/kernel/vdso64/gettimeofday.S:127
  127   
/build/linux-ZIBxfV/linux-4.15.0/arch/powerpc/kernel/vdso64/gettimeofday.S: No 
such file or directory.
  (gdb) bt
  #0  __kernel_clock_gettime () at 
/build/linux-ZIBxfV/linux-4.15.0/arch/powerpc/kernel/vdso64/gettimeofday.S:127
  #1  0x00007ffff7b8f530 in ?? () from /lib/powerpc64le-linux-gnu/libc.so.6
  #2  0x00007ffff6b81118 in ?? () from 
/usr/lib/powerpc64le-linux-gnu/libcuda.so.1
  #3  0x00007ffff6a69c70 in ?? () from 
/usr/lib/powerpc64le-linux-gnu/libcuda.so.1
  #4  0x00007ffff6bf0ba0 in cuInit () from 
/usr/lib/powerpc64le-linux-gnu/libcuda.so.1
  #5  0x000000010003ca50 in cudart::__loadDriverInternalUtil() ()
  #6  0x00007ffff7f05274 in __pthread_once_slow (
      once_control=0x1000c00f0 
<cudart::globalState::loadDriver()::loadDriverControl>,
      init_routine=0x10003c950 <cudart::__loadDriverInternalUtil()>) at 
pthread_once.c:116
  #7  0x000000010008ea88 in cudart::cuosOnce(int*, void (*)()) ()
  #8  0x00000001000410a8 in cudart::globalState::initializeDriver() ()
  #9  0x000000010005ec90 in cudaGetDeviceCount ()
  #10 0x0000000100009930 in gpuGetMaxGflopsDeviceId() ()
  #11 0x0000000100009bf4 in findCudaDevice(int, char const**) ()
  #12 0x000000010000836c in main ()
  (gdb) step
  128   in 
/build/linux-ZIBxfV/linux-4.15.0/arch/powerpc/kernel/vdso64/gettimeofday.S
  (gdb) bt
  #0  __kernel_clock_gettime () at 
/build/linux-ZIBxfV/linux-4.15.0/arch/powerpc/kernel/vdso64/gettimeofday.S:128
  #1  0x0000000000000000 in ?? ()
  (gdb)

  Note: __kernel_clock_gettime+144 is currently the point in the
  function at which the syscall made, and is liable to change if
  updated. It corresponds to the "sc" instruction here:
  https://gitlab.com/TeeFirefly/linux-
  
kernel/blob/7408b38cfdf9b0c6c3bda97402c75bd27ef69a85/arch/powerpc/kernel/vdso64/gettimeofday.S#L127
  and can be rediscovered if needed by disassembling the function.

  Note that a backtrace can be collected before entering the syscall,
  but not during. The inability to unwind also prevents GDB from being
  able to "finish" (step out of) the function:

  (gdb) finish
  Run till exit from #0  __kernel_clock_gettime ()
      at 
/build/linux-ZIBxfV/linux-4.15.0/arch/powerpc/kernel/vdso64/gettimeofday.S:128
  Warning:
  Cannot insert breakpoint 0.
  Cannot access memory at address 0x0

  Command aborted.
  (gdb)

  The cause of the issue is a lack of Call Frame Information (CFI) in
  the syscall code path, and so a potential fix here could be to save
  the link register and add the corresponding CFI directive for the
  syscall code path (as is done for the alternative code path).[Less]

  This is now upstream accepted in the powerpc tree as git commit
  
https://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux.git/commit/?h=next&id=56d20861c027498b5a1112b4f9f05b56d906fdda
  ("powerpc/vdso: Correct call frame information")

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