# Re: arm64/acpi: NULL dereference reports from UBSAN at boot

- From: Hanjun Guo \<guohanjun@huawei.com\>
- Date: 2020-05-22 08:07:25 
- List: linux-arm-kernel
- Page: https://ratatoskr.run/linux-arm-kernel/2020/05/5974720
- Thread: https://ratatoskr.run/linux-arm-kernel/2020/05/5973580/t.md

```text
Hi Will,

On 2020/5/21 18:09, Will Deacon wrote:
> Hi folks,
>
> I just tried booting the arm64 for-kernelci branch under QEMU (version
> 4.2.50 (v4.2.0-779-g4354edb6dcc7)) with UBSAN enabled, and I see a couple
> of NULL pointer dereferences reported at boot. I think they're both GIC
> related (log below). I don't see a panic with UBSAN disabled, so something's
> fishy here.
>
> Please can you take a look when you get a chance? I haven't had time to see
> if this is a regression or not, but I don't think it's particularly serious
> as I have all sorts of horrible stuff enabled in my .config, since I'm
> trying to chase down another bug:
>
> https://git.kernel.org/pub/scm/linux/kernel/git/mark/linux.git/plain/arch/arm64/configs/fuzzing.config?h=fuzzing/arm64-kernelci-20200519&id=c149cf6a51aa4f72d53fc681c6661094e93ef660
>
> (on top of defconfig)
>
> CONFIG_FAIL_PAGE_ALLOC may be to blame.

I enabled UBSAN and CONFIG_FAIL_PAGE_ALLOC on top of defconfig,
testing against the for-kernelci branch on the D06 board, I
can see some UBSAN warnings from megaraid_sas driver [0], but not
from any other subsystem including ACPI, I will try all your
configs above to see if I can get more warnings.

Thanks
Hanjun

[0]:
[   18.244272] ================================================================================
[   18.252673] UBSAN: array-index-out-of-bounds in drivers/scsi/megaraid/megaraid_sas_fp.c:104:32
[   18.261244] index 1 is out of range for type 'MR_LD_SPAN_MAP [1]'
[   18.267313] CPU: 0 PID: 656 Comm: kworker/0:1 Not tainted 5.7.0-rc6-1-14703-gf4582661223d-dirty #20
[   18.276314] Hardware name: Huawei TaiShan 2280 V2/BC82AMDC, BIOS 2280-V2 CS V3.B210.01 03/12/2020
[   18.285151] Workqueue: events work_for_cpu_fn
[   18.289488] Call trace:
[   18.291925]  dump_backtrace+0x0/0x248
[   18.295572]  show_stack+0x18/0x28
[   18.298873]  dump_stack+0xc0/0x10c
[   18.302261]  ubsan_epilogue+0x10/0x58
[   18.305905]  __ubsan_handle_out_of_bounds+0x8c/0xa8
[   18.310763]  mr_update_load_balance_params+0x118/0x120
[   18.315877]  MR_ValidateMapInfo+0x300/0xb00
[   18.320040]  megasas_get_map_info+0x134/0x1f8
[   18.324377]  megasas_init_adapter_fusion+0xba8/0x10a0
[   18.329403]  megasas_probe_one+0x6e0/0x1b70
[   18.333569]  local_pci_probe+0x40/0xb0
[   18.337299]  work_for_cpu_fn+0x1c/0x30
[   18.341031]  process_one_work+0x1f8/0x378
[   18.345022]  worker_thread+0x21c/0x4c0
[   18.348753]  kthread+0x150/0x158
[   18.351967]  ret_from_fork+0x10/0x18
[   18.355529] ================================================================================

[   18.592274] ================================================================================
[   18.600672] UBSAN: array-index-out-of-bounds in drivers/scsi/megaraid/megaraid_sas_fp.c:141:9
[   18.609155] index 1 is out of range for type 'MR_LD_SPAN_MAP [1]'
[   18.615221] CPU: 0 PID: 656 Comm: kworker/0:1 Not tainted 5.7.0-rc6-1-14703-gf4582661223d-dirty #20
[   18.624222] Hardware name: Huawei TaiShan 2280 V2/BC82AMDC, BIOS 2280-V2 CS V3.B210.01 03/12/2020
[   18.633050] Workqueue: events work_for_cpu_fn
[   18.637387] Call trace:
[   18.639822]  dump_backtrace+0x0/0x248
[   18.643467]  show_stack+0x18/0x28
[   18.646767]  dump_stack+0xc0/0x10c
[   18.650152]  ubsan_epilogue+0x10/0x58
[   18.653796]  __ubsan_handle_out_of_bounds+0x8c/0xa8
[   18.658652]  MR_GetLDTgtId+0x58/0x60
[   18.662211]  megasas_sync_map_info+0xd0/0x1c0
[   18.666547]  megasas_init_adapter_fusion+0xd60/0x10a0
[   18.671574]  megasas_probe_one+0x6e0/0x1b70
[   18.675736]  local_pci_probe+0x40/0xb0
[   18.679466]  work_for_cpu_fn+0x1c/0x30
[   18.683197]  process_one_work+0x1f8/0x378
[   18.687188]  worker_thread+0x21c/0x4c0
[   18.690920]  kthread+0x150/0x158
[   18.694123]  ret_from_fork+0x10/0x18
[   18.697683] ================================================================================


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