Re: [PATCH v3 3/5] libnvdimm/namespace: Enforce memremap_compat_align()

["Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>]

Dan Williams <dan.j.williams@intel.com> 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, and nd_dax cases. This includes
> preventing the creation of namespaces where the base address is
> misaligned and cases there infoblock padding parameters are invalid.
>

Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>

> Reported-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
> Cc: Jeff Moyer <jmoyer@redhat.com>
> Fixes: a3619190d62e ("libnvdimm/pfn: stop padding pmem namespaces to section alignment")
> Signed-off-by: Dan Williams <dan.j.williams@intel.com>
> ---
>  drivers/nvdimm/namespace_devs.c |   12 ++++++++++++
>  drivers/nvdimm/pfn_devs.c       |   26 +++++++++++++++++++++++---
>  2 files changed, 35 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/nvdimm/namespace_devs.c b/drivers/nvdimm/namespace_devs.c
> index 032dc61725ff..68e89855f779 100644
> --- a/drivers/nvdimm/namespace_devs.c
> +++ b/drivers/nvdimm/namespace_devs.c
> @@ -10,6 +10,7 @@
>  #include <linux/nd.h>
>  #include "nd-core.h"
>  #include "pmem.h"
> +#include "pfn.h"
>  #include "nd.h"
>  
>  static void namespace_io_release(struct device *dev)
> @@ -1739,6 +1740,17 @@ struct nd_namespace_common *nvdimm_namespace_common_probe(struct device *dev)
>  		return ERR_PTR(-ENODEV);
>  	}

May be add a comment here that both dax/fsdax namespace details are
checked in nd_pfn_validate() so that we look at start_pad and end_trunc
while validating the namespace?

>  
> +	if (pmem_should_map_pages(dev)) {
> +		struct nd_namespace_io *nsio = to_nd_namespace_io(&ndns->dev);
> +		struct resource *res = &nsio->res;
> +
> +		if (!IS_ALIGNED(res->start | (res->end + 1),
> +					memremap_compat_align())) {
> +			dev_err(&ndns->dev, "%pr misaligned, unable to map\n", res);
> +			return ERR_PTR(-EOPNOTSUPP);
> +		}
> +	}
> +
>  	if (is_namespace_pmem(&ndns->dev)) {
>  		struct nd_namespace_pmem *nspm;
>  
> diff --git a/drivers/nvdimm/pfn_devs.c b/drivers/nvdimm/pfn_devs.c
> index 79fe02d6f657..3bdd4b883d05 100644
> --- a/drivers/nvdimm/pfn_devs.c
> +++ b/drivers/nvdimm/pfn_devs.c
> @@ -446,6 +446,7 @@ static bool nd_supported_alignment(unsigned long align)
>  int nd_pfn_validate(struct nd_pfn *nd_pfn, const char *sig)
>  {
>  	u64 checksum, offset;
> +	struct resource *res;
>  	enum nd_pfn_mode mode;
>  	struct nd_namespace_io *nsio;
>  	unsigned long align, start_pad;
> @@ -578,13 +579,14 @@ int nd_pfn_validate(struct nd_pfn *nd_pfn, const char *sig)
>  	 * established.
>  	 */
>  	nsio = to_nd_namespace_io(&ndns->dev);
> -	if (offset >= resource_size(&nsio->res)) {
> +	res = &nsio->res;
> +	if (offset >= resource_size(res)) {
>  		dev_err(&nd_pfn->dev, "pfn array size exceeds capacity of %s\n",
>  				dev_name(&ndns->dev));
>  		return -EOPNOTSUPP;
>  	}
>  
> -	if ((align && !IS_ALIGNED(nsio->res.start + offset + start_pad, align))
> +	if ((align && !IS_ALIGNED(res->start + offset + start_pad, align))
>  			|| !IS_ALIGNED(offset, PAGE_SIZE)) {
>  		dev_err(&nd_pfn->dev,
>  				"bad offset: %#llx dax disabled align: %#lx\n",
> @@ -592,6 +594,18 @@ int nd_pfn_validate(struct nd_pfn *nd_pfn, const char *sig)
>  		return -EOPNOTSUPP;
>  	}
>  
> +	if (!IS_ALIGNED(res->start + le32_to_cpu(pfn_sb->start_pad),
> +				memremap_compat_align())) {
> +		dev_err(&nd_pfn->dev, "resource start misaligned\n");
> +		return -EOPNOTSUPP;
> +	}
> +
> +	if (!IS_ALIGNED(res->end + 1 - le32_to_cpu(pfn_sb->end_trunc),
> +				memremap_compat_align())) {
> +		dev_err(&nd_pfn->dev, "resource end misaligned\n");
> +		return -EOPNOTSUPP;
> +	}
> +
>  	return 0;
>  }
>  EXPORT_SYMBOL(nd_pfn_validate);
> @@ -750,7 +764,13 @@ static int nd_pfn_init(struct nd_pfn *nd_pfn)
>  	start = nsio->res.start;
>  	size = resource_size(&nsio->res);
>  	npfns = PHYS_PFN(size - SZ_8K);
> -	align = max(nd_pfn->align, SUBSECTION_SIZE);
> +	align = max(nd_pfn->align, memremap_compat_align());
> +	if (!IS_ALIGNED(start, memremap_compat_align())) {
> +		dev_err(&nd_pfn->dev, "%s: start %pa misaligned to %#lx\n",
> +				dev_name(&ndns->dev), &start,
> +				memremap_compat_align());
> +		return -EINVAL;
> +	}

This validates start in case of a new namespace creation where the user
updated nd_region->align value? A comment there would help when looking
at the code later?

>  	end_trunc = start + size - ALIGN_DOWN(start + size, align);
>  	if (nd_pfn->mode == PFN_MODE_PMEM) {
>  		/*
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