linux-kernel - Re: [PATCH] libnvdimm, pmem: fix badblocks notification crash

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Message-ID: <CAPcyv4jFk2nAdhViv_3CWQ7UxE=OCYro-d2OW-yAFAsxVUQWZw@mail.gmail.com>
Date:   Thu, 27 Apr 2017 15:26:49 -0700
From:   Dan Williams <dan.j.williams@...el.com>
To:     "Kani, Toshimitsu" <toshi.kani@....com>
Cc:     "linux-nvdimm@...ts.01.org" <linux-nvdimm@...ts.01.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
        "Verma, Vishal L" <vishal.l.verma@...el.com>
Subject: Re: [PATCH] libnvdimm, pmem: fix badblocks notification crash

On Thu, Apr 27, 2017 at 3:25 PM, Kani, Toshimitsu <toshi.kani@....com> wrote:
> On Thu, 2017-04-27 at 15:10 -0700, Dan Williams wrote:
>> The nd_pmem_notify() routine is called whenever an ARS
>> (address-range-scrub) completes to communicate results to the
>> per-namespace badblocks instances.
>>
>> When the namespace is in btt mode we crash because we do not allocate
>> a struct pmem_device instance in that case. Resulting in the
>> following crash signature:
>>
>>  BUG: unable to handle kernel NULL pointer dereference at
>> 0000000000000030
>>  IP: nd_pmem_notify+0x30/0xf0 [nd_pmem]
>>  Call Trace:
>>   nd_device_notify+0x40/0x50
>>   child_notify+0x10/0x20
>>   device_for_each_child+0x50/0x90
>>   nd_region_notify+0x20/0x30
>>   nd_device_notify+0x40/0x50
>>   nvdimm_region_notify+0x27/0x30
>>   acpi_nfit_scrub+0x341/0x590 [nfit]
>>   process_one_work+0x197/0x450
>>   worker_thread+0x4e/0x4a0
>>   kthread+0x109/0x140
>>
>> Given that we don't even populate the btt badblocks instance, just
>> return early and skip the device to region lookup.
>
> We populate the btt badblocks into nsio->bb, and check/clear them in
> nsio_rw_bytes().

Argh, yes, we don't populate them out to the disk badblocks. I'll go
with your patch.