Re: [PATCH 3/5] libnvdimm/namespace: Enforce memremap_compat_align()

[Aneesh Kumar K.V]

Dan Williams <dan.j.williams@xxxxxxxxx> writes:

> The pmem driver on PowerPC crashes with the following signature when
> instantiating misaligned namespaces that map their capacity via
> memremap_pages().
>
>     BUG: Unable to handle kernel data access at 0xc001000406000000
>     Faulting instruction address: 0xc000000000090790
>     NIP [c000000000090790] arch_add_memory+0xc0/0x130
>     LR [c000000000090744] arch_add_memory+0x74/0x130
>     Call Trace:
>      arch_add_memory+0x74/0x130 (unreliable)
>      memremap_pages+0x74c/0xa30
>      devm_memremap_pages+0x3c/0xa0
>      pmem_attach_disk+0x188/0x770
>      nvdimm_bus_probe+0xd8/0x470
>
> With the assumption that only memremap_pages() has alignment
> constraints, enforce memremap_compat_align() for
> pmem_should_map_pages(), nd_pfn, or nd_dax cases.
>

Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxx>

> Reported-by: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxx>
> Cc: Jeff Moyer <jmoyer@xxxxxxxxxx>
> Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
> ---
>  drivers/nvdimm/namespace_devs.c |   10 ++++++++++
>  1 file changed, 10 insertions(+)
>
> diff --git a/drivers/nvdimm/namespace_devs.c b/drivers/nvdimm/namespace_devs.c
> index 032dc61725ff..aff1f32fdb4f 100644
> --- a/drivers/nvdimm/namespace_devs.c
> +++ b/drivers/nvdimm/namespace_devs.c
> @@ -1739,6 +1739,16 @@ struct nd_namespace_common *nvdimm_namespace_common_probe(struct device *dev)
>  		return ERR_PTR(-ENODEV);
>  	}
>  
> +	if (pmem_should_map_pages(dev) || nd_pfn || nd_dax) {
> +		struct nd_namespace_io *nsio = to_nd_namespace_io(&ndns->dev);
> +		resource_size_t start = nsio->res.start;
> +
> +		if (!IS_ALIGNED(start | size, memremap_compat_align())) {
> +			dev_dbg(&ndns->dev, "misaligned, unable to map\n");
> +			return ERR_PTR(-EOPNOTSUPP);
> +		}
> +	}
> +
>  	if (is_namespace_pmem(&ndns->dev)) {
>  		struct nd_namespace_pmem *nspm;
>  
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