[BUG] commit 444d13ff10f introduced boot failure on s390x

[Eryu Guan]

Hi,

I hit boot failure on s390x host starting from 4.8-rc1 kernel, 4.7
kernel works fine. And I bisected to this commit 444d13ff10fb

    commit 444d13ff10fb13bc3e64859c3cf9ce43dcfeb075
    Author: Jessica Yu <jeyu@xxxxxxxxxx>
    Date:   Wed Jul 27 12:06:21 2016 +0930
    
        modules: add ro_after_init support
    
        Add ro_after_init support for modules by adding a new page-aligned section
        in the module layout (after rodata) for ro_after_init data and enabling RO
        protection for that section after module init runs.
    
        Signed-off-by: Jessica Yu <jeyu@xxxxxxxxxx>
        Acked-by: Kees Cook <keescook@xxxxxxxxxxxx>
        Signed-off-by: Rusty Russell <rusty@xxxxxxxxxxxxxxx>

and I've only hit this panic on s390x hosts. Console log is appended at
the end of email.

Thanks,
Eryu

[    2.050197] device-mapper: uevent: version 1.0.3
[    2.050370] device-mapper: ioctl: 4.34.0-ioctl (2015-10-28) initialised: dm-d
evel@xxxxxxxxxx
[    2.057615] Unable to handle kernel pointer dereference in virtual kernel add
ress space
[    2.057619] Failing address: 000003ff8001d000 TEID: 000003ff8001d407
[    2.057620] Fault in home space mode while using kernel ASCE.
[    2.057622] AS:0000000000a7c007 R3:000000007c974007 S:000000007cc24800 P:0000
00000239b21d
[    2.057665] Oops: 0004 ilc:3 [#1] SMP
[    2.057667] Modules linked in: dm_mod
[    2.057670] CPU: 0 PID: 399 Comm: modprobe Not tainted 4.7.0+ #7
[    2.057672] Hardware name: IBM              2827 H43              400
      (z/VM)
[    2.057673] task: 000000007cccd100 ti: 0000000002324000 task.ti: 000000000232
4000
[    2.057675] Krnl PSW : 0704c00180000000 000000000043a5c8 (__list_add_rcu+0x50
/0xa8)
[    2.057683]            R:0 T:1 IO:1 EX:1 Key:0 M:1 W:0 P:0 AS:3 CC:0 PM:0 RI:
0 EA:3
Krnl GPRS: 0000000000000006 000000000098b278 000003ff80117208 000000000098b278
[    2.057685]            000003ff8001df08 00000000001c913c 0000000000000002 000
000008001e55c
[    2.057686]            0000000000000560 0000000002327e00 000003ff80117218 000
003ff80117208
[    2.057687]            000000000098b278 000003ff8001df08 0000000002327cc0 000
0000002327c90
[    2.057696] Krnl Code: 000000000043a5b6: e3d0b0000024        stg     %r13,0(%
r11)
           000000000043a5bc: e3c0b0080024       stg     %r12,8(%r11)
          #000000000043a5c2: e3b0c0000024       stg     %r11,0(%r12)
          >000000000043a5c8: e3b0d0080024       stg     %r11,8(%r13)
           000000000043a5ce: e340f0b80004       lg      %r4,184(%r15)
           000000000043a5d4: ebbff0a00004       lmg     %r11,%r15,160(%r15)
           000000000043a5da: 07f4               bcr     15,%r4
           000000000043a5dc: e34040080004       lg      %r4,8(%r4)
[    2.057706] Call Trace:
[    2.057708] ([<0000000002327cc0>] 0x2327cc0)
[    2.057714] ([<00000000001c98d0>] load_module+0x8e0/0x1870)
[    2.057715] ([<00000000001caa74>] SyS_finit_module+0xb4/0xf0)
[    2.057720] ([<00000000006678b6>] system_call+0xd6/0x264)
[    2.057721] Last Breaking-Event-Address:
[    2.057722]  [<00000000001c98ca>] load_module+0x8da/0x1870
[    2.057723]
[    2.057724] Kernel panic - not syncing: Fatal exception: panic_on_oops