Re: [PATCH] cxl/acpi: Annotate struct cxl_cxims_data with __counted_by

From: Gustavo A. R. Silva
Date: Sat Sep 23 2023 - 04:58:47 EST


On Fri, Sep 22, 2023 at 10:53:19AM -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 cxl_cxims_data.
> 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: Davidlohr Bueso <dave@xxxxxxxxxxxx>
> Cc: Jonathan Cameron <jonathan.cameron@xxxxxxxxxx>
> Cc: Dave Jiang <dave.jiang@xxxxxxxxx>
> Cc: Alison Schofield <alison.schofield@xxxxxxxxx>
> Cc: Vishal Verma <vishal.l.verma@xxxxxxxxx>
> Cc: Ira Weiny <ira.weiny@xxxxxxxxx>
> Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
> Cc: linux-cxl@xxxxxxxxxxxxxxx
> Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>

Reviewed-by: Gustavo A. R. Silva <gustavoars@xxxxxxxxxx>

Thanks
--
Gustavo

> ---
> drivers/cxl/acpi.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/cxl/acpi.c b/drivers/cxl/acpi.c
> index d1c559879dcc..40d055560e52 100644
> --- a/drivers/cxl/acpi.c
> +++ b/drivers/cxl/acpi.c
> @@ -14,7 +14,7 @@
>
> struct cxl_cxims_data {
> int nr_maps;
> - u64 xormaps[];
> + u64 xormaps[] __counted_by(nr_maps);
> };
>
> /*
> @@ -112,9 +112,9 @@ static int cxl_parse_cxims(union acpi_subtable_headers *header, void *arg,
> GFP_KERNEL);
> if (!cximsd)
> return -ENOMEM;
> + cximsd->nr_maps = nr_maps;
> memcpy(cximsd->xormaps, cxims->xormap_list,
> nr_maps * sizeof(*cximsd->xormaps));
> - cximsd->nr_maps = nr_maps;
> cxlrd->platform_data = cximsd;
>
> return 0;
> --
> 2.34.1
>
>