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

["lizhijian@fujitsu.com" <lizhijian@fujitsu.com>]

On 17/03/2023 13:59, Dan Williams wrote:
> lizhijian@fujitsu.com 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!
> 
> That's expected though,

Do you mean we just keep it as it is.


> you can't block libnvdimm_init and then expect
> modules that link to libnvdimm to work.
Ah, we would rather see it *unable to work* than panic, isn't it.



Thanks
Zhijian


> You would also need to block all
> modules / initcalls that depend on libnvdimm_init having runI'll
> respond to the other thread with some ideas.