4.7.6->4.8.1 Possible regression

[Alexander Shiyan]

Hello.

After a kernel update from 4.7.6 to 4.8.1, the bug appear once kernel run "init".
...
VFS: Mounted root (squashfs filesystem) readonly on device 31:3.
devtmpfs: mounted
Freeing unused kernel memory: 144K (c04da000 - c04fe000)
This architecture does not have kernel memory protection.

Please press Enter to activate this console.
starting pid 448, tty '': '-/bin/ash'
Unable to handle kernel NULL pointer dereference at virtual address 00000008
pgd = c3b58000
[00000008] *pgd=800000000, *pte=00000000, *ppte=feff4140
Internal error: Oops: 63c11817 [#1] PREEMPT ARM
CPU: 0 PID: 448 Comm: ash Not tainted 4.8.1+ #1
Hardware name: Cirrus Logic CLPS711X (Device Tree Support)
task: c39e03a0 ti: c3b4e000 task.ti: c3b4e000
PC is at __dabt_svc+0x4c/0x60
LR is at do_page_fault+0x144/0x2ac
pc : [<c000d3ac>]    lr : [<c000fcec>]    psr: 60000093
sp : c3b4fe6c  ip : 00000001  fp : b6f1bf88
r10: c387a5a0  r9 : 00000000  r8 : e4e0e001
r7 : bee3ef83  r6 : 00100000  r5 :  80000013 r4 : c022fcf8
r3 : 00000000  r2 : 00000008  r1 : bf000000  r0 : 00000000
Flags: nZCv  IRQs off  FIQs on  Mode SVC_32  ISA ARM  Segment user
Control: 0000217f  Table: c3b58055  DAC: 00000055
Process ash (pid: 448, stack limit = 0xc3b4e190)
Stack: (0xc3b4fe6c to 0xc3b50000)
fe60:                            bee3ef83 c05168d1 ffffffff 00000000 c3adfe80
fe80: c3a03300 00000000 c3b4fed0 c3a03400 bee3ef83 c387a5a0 b6f1bf88 00000001
fea0: c3b4febc 00000076 c022fcf8  80000013 ffffffff 0000003f bf000000 bee3ef83
fec0: 00000004 00000000 c3adfe80 c00e432c 00000812 00000005 00000001 00000006
fee0: b6f1b000 00000000 00010000 0003c944 0004d000 0004d439 00010000 b6f1b000
ff00: 00000005 00000000 00015ecc c3b4fed0 0000000a 00000000 00000000 c00a1dc0
ff20: befff000 c3a03300 c3b4e000 c0507cd8 c0508024 fffffff8 c3a03300 00000000
ff40: c0516a58 c00a35bc c39e03a0 000001c0 bea84ce8 0004e008 c3b3a000 c00a3ac0
ff60: c3b40374 c3b3a000 bea84d11 00000000 c0500188 bea84d11 bea84ce8 00000001
ff80: 0000000b c000a304 c3b4e000 00000000 bea84ce4 c00a3cd0 00000000 bea84d11
ffa0: bea84ce8 c000a160 bea84d11 bea84ce8 bea84d11 bea84ce8 0004e008 0004d450
ffc0: bea84d11 bea84ce8 00000001 0000000b b6f45ee4 00000000 b6f5ff70 bea84ce4
ffe0: b6f2f130 bea84cb0 b6f2f194 b6ef29f4 a0000010 bea84d11 02c7cffa 02c7cffd
[<c000d3ac>] (__dabt_svc) from [<c022fcf8>] (__copy_to_user_std+0xf8/0x330)
[<c022fcf8>] (__copy_to_user_std) from [<c00e432c>] (load_elf_binary+0x920/0x107c)
[<c00e432c>] (load_elf_binary) from [<c00a35bc>] (search_binary_handler+0x80/0x16c)
[<c00a35bc>] (search_binary_handler) from [<c00a3ac0>] (do_execveat_common+0x418/0x600)
[<c00a3ac0>] (do_execveat_common) from [<c00a3cd0>] (do_execve+0x28/0x30)
[<c00a3cd0>] (do_execve) from [<c000a160>] (ret_fast_syscall+0x0/0x30)
Code: e1a0200d eb00136b e321f093 e59d104c (e5891008)
---[ end trace 4b4f8086ebef98c5 ]---
process '-/bin/ash' (pid 448) exited. Scheduling for restart.


Git-bisect found a bad commit: "ARM: save and reset the address limit when entering an exception"
Reverting this commit on top of 4.8.1 solve this problem.

Can anyone have similar problems? Any ideas?

Thanks.
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