linux-kernel - [PATCH 4.13 045/110] libnvdimm, namespace: fix btt claim class crash

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Message-Id: <20171003114243.170269543@linuxfoundation.org>
Date:   Tue,  3 Oct 2017 14:29:07 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Vishal Verma <vishal.l.verma@...el.com>,
        "Maurice A. Saldivar" <maurice.a.saldivar@....com>,
        Dan Williams <dan.j.williams@...el.com>
Subject: [PATCH 4.13 045/110] libnvdimm, namespace: fix btt claim class crash

4.13-stable review patch.  If anyone has any objections, please let me know.

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

From: Dan Williams <dan.j.williams@...el.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@...el.com>
Reported-by: Maurice A. Saldivar <maurice.a.saldivar@....com>
Tested-by: Maurice A. Saldivar <maurice.a.saldivar@....com>
Signed-off-by: Dan Williams <dan.j.williams@...el.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.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;