Re: [PATCH] libnvdimm: Annotate struct nd_region with __counted_by

[Verma, Vishal L]

On Fri, 2023-09-22 at 10:52 -0700, Kees Cook wrote:
> 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@xxxxxxxxx>
> Cc: Vishal Verma <vishal.l.verma@xxxxxxxxx>
> Cc: Dave Jiang <dave.jiang@xxxxxxxxx>
> Cc: Ira Weiny <ira.weiny@xxxxxxxxx>
> Cc: nvdimm@xxxxxxxxxxxxxxx
> Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
> ---
>  drivers/nvdimm/nd.h          | 2 +-
>  drivers/nvdimm/region_devs.c | 2 +-
>  2 files changed, 2 insertions(+), 2 deletions(-)

Reviewed-by: Vishal Verma <vishal.l.verma@xxxxxxxxx>

> 
> 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;