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 ib_pkey_cache.

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

Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Leon Romanovsky <leon@kernel.org>
Cc: "Håkon Bugge" <haakon.bugge@oracle.com>
Cc: Avihai Horon <avihaih@nvidia.com>
Cc: Anand Khoje <anand.a.khoje@oracle.com>
Cc: Mark Bloch <mbloch@nvidia.com>
Cc: linux-rdma@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
---
 drivers/infiniband/core/cache.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/infiniband/core/cache.c b/drivers/infiniband/core/cache.c
index 7acc0f936dad..c02a96d3572a 100644
--- a/drivers/infiniband/core/cache.c
+++ b/drivers/infiniband/core/cache.c
@@ -46,7 +46,7 @@
 
 struct ib_pkey_cache {
 	int             table_len;
-	u16             table[];
+	u16             table[] __counted_by(table_len);
 };
 
 struct ib_update_work {
-- 
2.34.1