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Subject[PATCH 4.13 045/110] libnvdimm, namespace: fix btt claim class crash
Date
4.13-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Dan Williams <dan.j.williams@intel.com>

commit 33a56086712561b8b9cdc881e0317f4c36861f72 upstream.

Maurice reports:

BUG: unable to handle kernel NULL pointer dereference at 0000000000000028
IP: holder_class_store+0x253/0x2b0 [libnvdimm]

...while trying to reconfigure an NVDIMM-N namespace into 'sector' /
'btt' mode. The crash points to this line:

(gdb) li *(holder_class_store+0x253)
0x7773 is in holder_class_store (drivers/nvdimm/namespace_devs.c:1420).
1415 for (i = 0; i < nd_region->ndr_mappings; i++) {
1416 struct nd_mapping *nd_mapping = &nd_region->mapping[i];
1417 struct nvdimm_drvdata *ndd = to_ndd(nd_mapping);
1418 struct nd_namespace_index *nsindex;
1419
1420 nsindex = to_namespace_index(ndd, ndd->ns_current);

...where we are failing because ndd is NULL due to NVDIMM-N dimms not
supporting labels.

Long story short, default to the BTTv1 format in the label-less /
NVDIMM-N case.

Fixes: 14e494542636 ("libnvdimm, btt: BTT updates for UEFI 2.7 format")
Cc: Vishal Verma <vishal.l.verma@intel.com>
Reported-by: Maurice A. Saldivar <maurice.a.saldivar@hpe.com>
Tested-by: Maurice A. Saldivar <maurice.a.saldivar@hpe.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/nvdimm/namespace_devs.c | 9 +++++++++
1 file changed, 9 insertions(+)

--- a/drivers/nvdimm/namespace_devs.c
+++ b/drivers/nvdimm/namespace_devs.c
@@ -1417,6 +1417,15 @@ static int btt_claim_class(struct device
struct nvdimm_drvdata *ndd = to_ndd(nd_mapping);
struct nd_namespace_index *nsindex;

+ /*
+ * If any of the DIMMs do not support labels the only
+ * possible BTT format is v1.
+ */
+ if (!ndd) {
+ loop_bitmask = 0;
+ break;
+ }
+
nsindex = to_namespace_index(ndd, ndd->ns_current);
if (nsindex == NULL)
loop_bitmask |= 1;

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