[PATCH] tools/testing/nvdimm: Stop read past end of global handle array

[Alison Schofield <alison.schofield@intel.com>]

KASAN reports a global-out-of-bounds access when running these nfit
tests: clear.sh, pmem-errors, pfn-meta-errors.sh, btt-errors.sh,
daxdev-errors.sh, and inject-error.sh.

[] BUG: KASAN: global-out-of-bounds in nfit_test_ctl+0x769f/0x7840 [nfit_test]
[] Read of size 4 at addr ffffffffc03ea01c by task ndctl/1215
[] The buggy address belongs to the variable:
[] handle+0x1c/0x1df4 [nfit_test]

The nfit_test mock platform defines a static table of 7 NFIT DIMM
handles, but nfit_test.0 builds 8 mock DIMMs total (5 DCR + 3 PM).
When the final DIMM (id == 7) is selected, this code:
    spa->devices[0].nfit_device_handle = handle[nvdimm->id];
indexes past the end of the 7-entry table, triggering KASAN.

Fix this by adding an eighth entry to the handle[] table and a
defensive bounds check so the test fails cleanly instead of
dereferencing out-of-bounds memory.

To generate a unique handle, the new entry sets the 'imc' field rather
than the 'chan' field. This matches the pattern of earlier entries
and avoids introducing a non-zero 'chan' which is never used in the
table. Computing the new handle shows no collision.

Notes from spelunkering for a Fixes Tag:

Commit 209851649dc4 ("acpi: nfit: Add support for hot-add") increased
the mock DIMMs to eight yet kept the handle[] array at seven.

Commit 10246dc84dfc ("acpi nfit: nfit_test supports translate SPA")
began using the last mock DIMM, triggering the KASAN.

Commit af31b04b67f4 ("tools/testing/nvdimm: Fix the array size for
dimm devices.") addressed a related KASAN warning but not the actual
handle array length.

Fixes: 209851649dc4 ("acpi: nfit: Add support for hot-add")
Cc: <stable@vger.kernel.org>
Signed-off-by: Alison Schofield <alison.schofield@intel.com>
---
 tools/testing/nvdimm/test/nfit.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/tools/testing/nvdimm/test/nfit.c b/tools/testing/nvdimm/test/nfit.c
index cfd4378e2129..cdbf9e8ee80a 100644
--- a/tools/testing/nvdimm/test/nfit.c
+++ b/tools/testing/nvdimm/test/nfit.c
@@ -129,6 +129,7 @@ static u32 handle[] = {
 	[4] = NFIT_DIMM_HANDLE(0, 1, 0, 0, 0),
 	[5] = NFIT_DIMM_HANDLE(1, 0, 0, 0, 0),
 	[6] = NFIT_DIMM_HANDLE(1, 0, 0, 0, 1),
+	[7] = NFIT_DIMM_HANDLE(1, 0, 1, 0, 1),
 };
 
 static unsigned long dimm_fail_cmd_flags[ARRAY_SIZE(handle)];
@@ -688,6 +689,13 @@ static int nfit_test_search_spa(struct nvdimm_bus *bus,
 	nd_mapping = &nd_region->mapping[nd_region->ndr_mappings - 1];
 	nvdimm = nd_mapping->nvdimm;
 
+	if (WARN_ON_ONCE(nvdimm->id >= ARRAY_SIZE(handle))) {
+		dev_err(&bus->dev,
+			"invalid nvdimm->id %u >= handle array size %zu\n",
+			nvdimm->id, ARRAY_SIZE(handle));
+		return -EINVAL;
+	}
+
 	spa->devices[0].nfit_device_handle = handle[nvdimm->id];
 	spa->num_nvdimms = 1;
 	spa->devices[0].dpa = dpa;

base-commit: 211ddde0823f1442e4ad052a2f30f050145ccada
-- 
2.37.3