[PATCH] pmem: fix a NULL pointer BUG in nd_pmem_notify

From: Toshi Kani
Date: Tue Apr 25 2017 - 19:04:54 EST


The following BUG was observed when nd_pmem_notify() was called
for a BTT device. The use of a pmem_device pointer is not valid
with BTT.

BUG: unable to handle kernel NULL pointer dereference at 0000000000000030
IP: nd_pmem_notify+0x30/0xf0 [nd_pmem]
Call Trace:
nd_device_notify+0x40/0x50
child_notify+0x10/0x20
device_for_each_child+0x50/0x90
nd_region_notify+0x20/0x30
nd_device_notify+0x40/0x50
nvdimm_region_notify+0x27/0x30
acpi_nfit_scrub+0x341/0x590 [nfit]
process_one_work+0x197/0x450
worker_thread+0x4e/0x4a0
kthread+0x109/0x140

Fix nd_pmem_notify() by setting nd_region and badblocks pointers
properly for BTT.

Signed-off-by: Toshi Kani <toshi.kani@xxxxxxx>
Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
Cc: Vishal Verma <vishal.l.verma@xxxxxxxxx>
---
drivers/nvdimm/pmem.c | 37 +++++++++++++++++++++++++------------
1 file changed, 25 insertions(+), 12 deletions(-)

diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c
index 5b536be..0fc1826 100644
--- a/drivers/nvdimm/pmem.c
+++ b/drivers/nvdimm/pmem.c
@@ -388,12 +388,12 @@ static void nd_pmem_shutdown(struct device *dev)

static void nd_pmem_notify(struct device *dev, enum nvdimm_event event)
{
- struct pmem_device *pmem = dev_get_drvdata(dev);
- struct nd_region *nd_region = to_region(pmem);
+ struct nd_region *nd_region;
resource_size_t offset = 0, end_trunc = 0;
struct nd_namespace_common *ndns;
struct nd_namespace_io *nsio;
struct resource res;
+ struct badblocks *bb;

if (event != NVDIMM_REVALIDATE_POISON)
return;
@@ -402,20 +402,33 @@ static void nd_pmem_notify(struct device *dev, enum nvdimm_event event)
struct nd_btt *nd_btt = to_nd_btt(dev);

ndns = nd_btt->ndns;
- } else if (is_nd_pfn(dev)) {
- struct nd_pfn *nd_pfn = to_nd_pfn(dev);
- struct nd_pfn_sb *pfn_sb = nd_pfn->pfn_sb;
+ nd_region = to_nd_region(ndns->dev.parent);
+ nsio = to_nd_namespace_io(&ndns->dev);
+ bb = &nsio->bb;
+ } else {
+ struct pmem_device *pmem = dev_get_drvdata(dev);

- ndns = nd_pfn->ndns;
- offset = pmem->data_offset + __le32_to_cpu(pfn_sb->start_pad);
- end_trunc = __le32_to_cpu(pfn_sb->end_trunc);
- } else
- ndns = to_ndns(dev);
+ nd_region = to_region(pmem);
+ bb = &pmem->bb;
+
+ if (is_nd_pfn(dev)) {
+ struct nd_pfn *nd_pfn = to_nd_pfn(dev);
+ struct nd_pfn_sb *pfn_sb = nd_pfn->pfn_sb;
+
+ ndns = nd_pfn->ndns;
+ offset = pmem->data_offset +
+ __le32_to_cpu(pfn_sb->start_pad);
+ end_trunc = __le32_to_cpu(pfn_sb->end_trunc);
+ } else {
+ ndns = to_ndns(dev);
+ }
+
+ nsio = to_nd_namespace_io(&ndns->dev);
+ }

- nsio = to_nd_namespace_io(&ndns->dev);
res.start = nsio->res.start + offset;
res.end = nsio->res.end - end_trunc;
- nvdimm_badblocks_populate(nd_region, &pmem->bb, &res);
+ nvdimm_badblocks_populate(nd_region, bb, &res);
}

MODULE_ALIAS("pmem");