cxl/acpi: Annotate struct cxl_cxims_data 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 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@stgolabs.net>
Cc: Jonathan Cameron <jonathan.cameron@huawei.com>
Cc: Dave Jiang <dave.jiang@intel.com>
Cc: Alison Schofield <alison.schofield@intel.com>
Cc: Vishal Verma <vishal.l.verma@intel.com>
Cc: Ira Weiny <ira.weiny@intel.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: linux-cxl@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Vishal Verma <vishal.l.verma@intel.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Link: https://lore.kernel.org/r/20230922175319.work.096-kees@kernel.org
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

diff --git a/drivers/cxl/acpi.c b/drivers/cxl/acpi.c
index d1c5598..40d0555 100644 (file)
--- 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;