When running the crash tool on a s390 live system we get a kernel panic
for reading memory within the kernel image:

 # uname -a
   Linux r3545011 4.14.0-rc8-00066-g1c9dbd46 #45 SMP PREEMPT Fri Nov 10 16:16:22 CET 2017 s390x s390x s390x GNU/Linux
 # crash /boot/vmlinux-devel /dev/mem
 # crash> rd 0x100000

 usercopy: kernel memory exposure attempt detected from 0000000000100000 (<kernel text>) (8 bytes)
 ------------[ cut here ]------------
 kernel BUG at mm/usercopy.c:72!
 illegal operation: 0001 ilc:1 [#1] PREEMPT SMP.
 Modules linked in:
 CPU: 0 PID: 1461 Comm: crash Not tainted 4.14.0-rc8-00066-g1c9dbd46-dirty #46
 Hardware name: IBM 2827 H66 706 (z/VM 6.3.0)
 task: 000000001ad10100 task.stack: 000000001df78000
 Krnl PSW : 0704d00180000000 000000000038165c (__check_object_size+0x164/0x1d0)
            R:0 T:1 IO:1 EX:1 Key:0 M:1 W:0 P:0 AS:3 CC:1 PM:0 RI:0 EA:3
 Krnl GPRS: 0000000012440e1d 0000000080000000 0000000000000061 00000000001cabc0
            00000000001cc6d6 0000000000000000 0000000000cc4ed2 0000000000001000
            000003ffc22fdd20 0000000000000008 0000000000100008 0000000000000001
            0000000000000008 0000000000100000 0000000000381658 000000001df7bc90
 Krnl Code: 000000000038164c: c020004a1c4a        larl    %r2,cc4ee0
            0000000000381652: c0e5fff2581b        brasl   %r14,1cc688
           #0000000000381658: a7f40001            brc     15,38165a
           >000000000038165c: eb42000c000c        srlg    %r4,%r2,12
            0000000000381662: eb32001c000c        srlg    %r3,%r2,28
            0000000000381668: c0110003ffff        lgfi    %r1,262143
            000000000038166e: ec31ff752065        clgrj   %r3,%r1,2,381558
            0000000000381674: a7f4ff67            brc     15,381542
 Call Trace:
 ([<0000000000381658>] __check_object_size+0x160/0x1d0)
  [<000000000082263a>] read_mem+0xaa/0x130.
  [<0000000000386182>] __vfs_read+0x42/0x168.
  [<000000000038632e>] vfs_read+0x86/0x140.
  [<0000000000386a26>] SyS_read+0x66/0xc0.
  [<0000000000ace6a4>] system_call+0xc4/0x2b0.
 INFO: lockdep is turned off.
 Last Breaking-Event-Address:
  [<0000000000381658>] __check_object_size+0x160/0x1d0

 Kernel panic - not syncing: Fatal exception: panic_on_oops

With CONFIG_HARDENED_USERCOPY copy_to_user() checks in __check_object_size()
if the source address is within the kernel image. When the crash tool reads
from 0x100000, this check leads to the kernel BUG().

So disable the kernel config option until this bug is fixed.

Corresponding bug report on LKML: https://lkml.org/lkml/2017/11/10/341Signed-off-by: Michael Holzheu <holzheu@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>