linux-hardening - [PATCH] libnvdimm: Annotate struct nd_region with __counted

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Date: Fri, 22 Sep 2023 10:52:39 -0700
From: Kees Cook <keescook@...omium.org>
To: Dan Williams <dan.j.williams@...el.com>
Cc: Kees Cook <keescook@...omium.org>,
	Vishal Verma <vishal.l.verma@...el.com>,
	Dave Jiang <dave.jiang@...el.com>,
	Ira Weiny <ira.weiny@...el.com>,
	nvdimm@...ts.linux.dev,
	Nathan Chancellor <nathan@...nel.org>,
	Nick Desaulniers <ndesaulniers@...gle.com>,
	Tom Rix <trix@...hat.com>,
	linux-kernel@...r.kernel.org,
	llvm@...ts.linux.dev,
	linux-hardening@...r.kernel.org
Subject: [PATCH] libnvdimm: Annotate struct nd_region with __counted_by

Prepare for the coming implementation by GCC and Clang of the __counted_by
attribute. Flexible array members annotated with __counted_by can have
their accesses bounds-checked at run-time checking via CONFIG_UBSAN_BOUNDS
(for array indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family
functions).

As found with Coccinelle[1], add __counted_by for struct nd_region.
Additionally, since the element count member must be set before accessing
the annotated flexible array member, move its initialization earlier.

[1] https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci

Cc: Dan Williams <dan.j.williams@...el.com>
Cc: Vishal Verma <vishal.l.verma@...el.com>
Cc: Dave Jiang <dave.jiang@...el.com>
Cc: Ira Weiny <ira.weiny@...el.com>
Cc: nvdimm@...ts.linux.dev
Signed-off-by: Kees Cook <keescook@...omium.org>
---
 drivers/nvdimm/nd.h          | 2 +-
 drivers/nvdimm/region_devs.c | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/nvdimm/nd.h b/drivers/nvdimm/nd.h
index e8b9d27dbb3c..ae2078eb6a62 100644
--- a/drivers/nvdimm/nd.h
+++ b/drivers/nvdimm/nd.h
@@ -422,7 +422,7 @@ struct nd_region {
 	struct nd_interleave_set *nd_set;
 	struct nd_percpu_lane __percpu *lane;
 	int (*flush)(struct nd_region *nd_region, struct bio *bio);
-	struct nd_mapping mapping[];
+	struct nd_mapping mapping[] __counted_by(ndr_mappings);
 };
 
 static inline bool nsl_validate_nlabel(struct nd_region *nd_region,
diff --git a/drivers/nvdimm/region_devs.c b/drivers/nvdimm/region_devs.c
index 0a81f87f6f6c..5be65fce85cf 100644
--- a/drivers/nvdimm/region_devs.c
+++ b/drivers/nvdimm/region_devs.c
@@ -1028,6 +1028,7 @@ static struct nd_region *nd_region_create(struct nvdimm_bus *nvdimm_bus,
 
 	if (!nd_region)
 		return NULL;
+	nd_region->ndr_mappings = ndr_desc->num_mappings;
 	/* CXL pre-assigns memregion ids before creating nvdimm regions */
 	if (test_bit(ND_REGION_CXL, &ndr_desc->flags)) {
 		nd_region->id = ndr_desc->memregion;
@@ -1062,7 +1063,6 @@ static struct nd_region *nd_region_create(struct nvdimm_bus *nvdimm_bus,
 
 		get_device(&nvdimm->dev);
 	}
-	nd_region->ndr_mappings = ndr_desc->num_mappings;
 	nd_region->provider_data = ndr_desc->provider_data;
 	nd_region->nd_set = ndr_desc->nd_set;
 	nd_region->num_lanes = ndr_desc->num_lanes;
-- 
2.34.1