nfit, libnvdimm: fix interleave set cookie calculation

The interleave-set cookie is a sum that sanity checks the composition of
an interleave set has not changed from when the namespace was initially
created. The checksum is calculated by sorting the DIMMs by their
location in the interleave-set. The comparison for the sort must be
64-bit wide, not byte-by-byte as performed by memcmp() in the broken
case.

Fix the implementation to accept correct cookie values in addition to
the Linux "memcmp" order cookies, but only allow correct cookies to be
generated going forward. It does mean that namespaces created by
third-party-tooling, or created by newer kernels with this fix, will not
validate on older kernels. However, there are a couple mitigating
conditions:

1/ platforms with namespace-label capable NVDIMMs are not widely
available.

2/ interleave-sets with a single-dimm are by definition not affected
(nothing to sort). This covers the QEMU-KVM NVDIMM emulation case.

The cookie stored in the namespace label will be fixed by any write the
namespace label, the most straightforward way to achieve this is to
write to the "alt_name" attribute of a namespace in sysfs.

Cc: <[e-mail]>
Fixes: eaf961536e16 ("libnvdimm, nfit: add interleave-set state-tracking infrastructure")
Reported-by: Nicholas Moulin <[e-mail]>
Tested-by: Nicholas Moulin <[e-mail]>
Signed-off-by: Dan Williams <[e-mail]>

drivers/acpi/nfit/core.c

···
 		+ num_mappings * sizeof(struct nfit_set_info_map);
 }
 
-static int cmp_map(const void *m0, const void *m1)
+static int cmp_map_compat(const void *m0, const void *m1)
 {
 	const struct nfit_set_info_map *map0 = m0;
 	const struct nfit_set_info_map *map1 = m1;
 
 	return memcmp(&map0->region_offset, &map1->region_offset,
 			sizeof(u64));
+}
+
+static int cmp_map(const void *m0, const void *m1)
+{
+	const struct nfit_set_info_map *map0 = m0;
+	const struct nfit_set_info_map *map1 = m1;
+
+	return map0->region_offset - map1->region_offset;
 }
 
 /* Retrieve the nth entry referencing this spa */
···
 	sort(&info->mapping[0], nr, sizeof(struct nfit_set_info_map),
 			cmp_map, NULL);
 	nd_set->cookie = nd_fletcher64(info, sizeof_nfit_set_info(nr), 0);
+
+	/* support namespaces created with the wrong sort order */
+	sort(&info->mapping[0], nr, sizeof(struct nfit_set_info_map),
+			cmp_map_compat, NULL);
+	nd_set->altcookie = nd_fletcher64(info, sizeof_nfit_set_info(nr), 0);
+
 	ndr_desc->nd_set = nd_set;
 	devm_kfree(dev, info);
 

drivers/nvdimm/namespace_devs.c

···
 struct device *create_namespace_pmem(struct nd_region *nd_region,
 		struct nd_namespace_label *nd_label)
 {
+	u64 altcookie = nd_region_interleave_set_altcookie(nd_region);
 	u64 cookie = nd_region_interleave_set_cookie(nd_region);
 	struct nd_label_ent *label_ent;
 	struct nd_namespace_pmem *nspm;
···
 	if (__le64_to_cpu(nd_label->isetcookie) != cookie) {
 		dev_dbg(&nd_region->dev, "invalid cookie in label: %pUb\n",
 				nd_label->uuid);
-		return ERR_PTR(-EAGAIN);
+		if (__le64_to_cpu(nd_label->isetcookie) != altcookie)
+			return ERR_PTR(-EAGAIN);
+
+		dev_dbg(&nd_region->dev, "valid altcookie in label: %pUb\n",
+				nd_label->uuid);
 	}
 
 	nspm = kzalloc(sizeof(*nspm), GFP_KERNEL);
···
 	res->name = dev_name(&nd_region->dev);
 	res->flags = IORESOURCE_MEM;
 
-	for (i = 0; i < nd_region->ndr_mappings; i++)
-		if (!has_uuid_at_pos(nd_region, nd_label->uuid, cookie, i))
-			break;
+	for (i = 0; i < nd_region->ndr_mappings; i++) {
+		if (has_uuid_at_pos(nd_region, nd_label->uuid, cookie, i))
+			continue;
+		if (has_uuid_at_pos(nd_region, nd_label->uuid, altcookie, i))
+			continue;
+		break;
+	}
+
 	if (i < nd_region->ndr_mappings) {
 		struct nvdimm_drvdata *ndd = to_ndd(&nd_region->mapping[i]);
 

drivers/nvdimm/nd.h

···
 int nd_region_to_nstype(struct nd_region *nd_region);
 int nd_region_register_namespaces(struct nd_region *nd_region, int *err);
 u64 nd_region_interleave_set_cookie(struct nd_region *nd_region);
+u64 nd_region_interleave_set_altcookie(struct nd_region *nd_region);
 void nvdimm_bus_lock(struct device *dev);
 void nvdimm_bus_unlock(struct device *dev);
 bool is_nvdimm_bus_locked(struct device *dev);

drivers/nvdimm/region_devs.c

···
 	return 0;
 }
 
+u64 nd_region_interleave_set_altcookie(struct nd_region *nd_region)
+{
+	struct nd_interleave_set *nd_set = nd_region->nd_set;
+
+	if (nd_set)
+		return nd_set->altcookie;
+	return 0;
+}
+
 void nd_mapping_free_labels(struct nd_mapping *nd_mapping)
 {
 	struct nd_label_ent *label_ent, *e;

include/linux/libnvdimm.h

···
 
 struct nd_interleave_set {
 	u64 cookie;
+	/* compatibility with initial buggy Linux implementation */
+	u64 altcookie;
 };
 
 struct nd_mapping_desc {