Re: [PATCH] pmem: fix a NULL pointer BUG in nd_pmem_notify

[Dan Williams]

On Tue, Apr 25, 2017 at 4:04 PM, Toshi Kani <toshi.kani@xxxxxxx> wrote:
> The following BUG was observed when nd_pmem_notify() was called
> for a BTT device.  The use of a pmem_device pointer is not valid
> with BTT.
>
>  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
>
> Fix nd_pmem_notify() by setting nd_region and badblocks pointers
> properly for BTT.
>
> Signed-off-by: Toshi Kani <toshi.kani@xxxxxxx>
> Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
> Cc: Vishal Verma <vishal.l.verma@xxxxxxxxx>


Hi Toshi, how did you trigger this? I'd like to get your test into the
regression suite.


> ---
>  drivers/nvdimm/pmem.c |   37 +++++++++++++++++++++++++------------
>  1 file changed, 25 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c
> index 5b536be..0fc1826 100644
> --- a/drivers/nvdimm/pmem.c
> +++ b/drivers/nvdimm/pmem.c
> @@ -388,12 +388,12 @@ static void nd_pmem_shutdown(struct device *dev)
>
>  static void nd_pmem_notify(struct device *dev, enum nvdimm_event event)
>  {
> -       struct pmem_device *pmem = dev_get_drvdata(dev);
> -       struct nd_region *nd_region = to_region(pmem);
> +       struct nd_region *nd_region;
>         resource_size_t offset = 0, end_trunc = 0;
>         struct nd_namespace_common *ndns;
>         struct nd_namespace_io *nsio;
>         struct resource res;
> +       struct badblocks *bb;
>
>         if (event != NVDIMM_REVALIDATE_POISON)
>                 return;
> @@ -402,20 +402,33 @@ static void nd_pmem_notify(struct device *dev, enum nvdimm_event event)
>                 struct nd_btt *nd_btt = to_nd_btt(dev);
>
>                 ndns = nd_btt->ndns;
> -       } else if (is_nd_pfn(dev)) {
> -               struct nd_pfn *nd_pfn = to_nd_pfn(dev);
> -               struct nd_pfn_sb *pfn_sb = nd_pfn->pfn_sb;
> +               nd_region = to_nd_region(ndns->dev.parent);
> +               nsio = to_nd_namespace_io(&ndns->dev);
> +               bb = &nsio->bb;
> +       } else {
> +               struct pmem_device *pmem = dev_get_drvdata(dev);
>
> -               ndns = nd_pfn->ndns;
> -               offset = pmem->data_offset + __le32_to_cpu(pfn_sb->start_pad);
> -               end_trunc = __le32_to_cpu(pfn_sb->end_trunc);
> -       } else
> -               ndns = to_ndns(dev);
> +               nd_region = to_region(pmem);
> +               bb = &pmem->bb;
> +
> +               if (is_nd_pfn(dev)) {
> +                       struct nd_pfn *nd_pfn = to_nd_pfn(dev);
> +                       struct nd_pfn_sb *pfn_sb = nd_pfn->pfn_sb;
> +
> +                       ndns = nd_pfn->ndns;
> +                       offset = pmem->data_offset +
> +                                       __le32_to_cpu(pfn_sb->start_pad);
> +                       end_trunc = __le32_to_cpu(pfn_sb->end_trunc);
> +               } else {
> +                       ndns = to_ndns(dev);
> +               }
> +
> +               nsio = to_nd_namespace_io(&ndns->dev);
> +       }
>
> -       nsio = to_nd_namespace_io(&ndns->dev);
>         res.start = nsio->res.start + offset;
>         res.end = nsio->res.end - end_trunc;
> -       nvdimm_badblocks_populate(nd_region, &pmem->bb, &res);
> +       nvdimm_badblocks_populate(nd_region, bb, &res);
>  }
>
>  MODULE_ALIAS("pmem");