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SubjectRe: [PATCH] nvdimm: nvdimm_bus_register: Avoid adding device to the unregistered bus
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, you can't block libnvdimm_init and then expect
modules that link to libnvdimm to work. You would also need to block all
modules / initcalls that depend on libnvdimm_init having run. I'll
respond to the other thread with some ideas.

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