Re: [PATCH] nvdimm: nvdimm_bus_register: Avoid adding device to the unregistered bus

[lizhijian@xxxxxxxxxxx]

On 17/03/2023 10:26, Dan Williams wrote:
> lizhijian@xxxxxxxxxxx wrote:
>>
>>
>> On 16/03/2023 23:54, Dan Williams wrote:
>>> Li Zhijian wrote:
>>>> nvdimm_bus_register() could be called from other modules, such as nfit,
>>>> but it can only be called after the nvdimm_bus_type is registered.
>>>>
>>>>    BUG: kernel NULL pointer dereference, address: 0000000000000098
>>>>    #PF: supervisor read access in kernel mode
>>>>    #PF: error_code(0x0000) - not-present page
>>>>    PGD 0 P4D 0
>>>>    Oops: 0000 [#1] PREEMPT SMP PTI
>>>>    CPU: 0 PID: 117 Comm: systemd-udevd Not tainted 6.2.0-rc6-pmem+ #97
>>>>    Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.0-0-gd239552ce722-prebuilt.qemu.org 04/01/2014
>>>>    RIP: 0010:bus_add_device+0x58/0x150
>>>>    Call Trace:
>>>>     <TASK>
>>>>     device_add+0x3ac/0x980
>>>>     nvdimm_bus_register+0x16d/0x1d0
>>>>     acpi_nfit_init+0xb72/0x1f90 [nfit]
>>>>     acpi_nfit_add+0x1d5/0x200 [nfit]
>>>>     acpi_device_probe+0x45/0x160
>>>
>>> Can you explain a bit more how to hit this crash? This has not been a
>>> problem historically and the explanation above makes it sound like this
>>> is a theoretical issue.
>>>
>>
>> Dan,
>>
>> Configure the kconfig with ACPI_NFIT [=m] && LIBNVDIMM [=y], and add extra kernel booting parameter
>> 'initcall_blacklist=libnvdimm_init'. Then kernel panic!
>> Theoretically, it will also happen if nvdimm_bus_register() failed.
>>
>>
>> For kdump purpose[1], we need to disable libnvdimm driver to ensure metadata in pmem will not be updated again in kdump kernel
>> [1]https://lore.kernel.org/linux-mm/3c752fc2-b6a0-2975-ffec-dba3edcf4155@xxxxxxxxxxx/T/
> 
> Ah, great write up! Let me give that some thought. 

That would be great.


> Apologies for missing it earlier.

Never mind :)



> 
> This would have been a good use for:
> 
> Link: https://lore.kernel.org/linux-mm/3c752fc2-b6a0-2975-ffec-dba3edcf4155@xxxxxxxxxxx
> 
> ...in the above changelog.


sounds good, i will update it in next version.


Thanks
Zhijian