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 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 nh_res_table.

Cc: David Ahern <dsah...@kernel.org>
Cc: "David S. Miller" <da...@davemloft.net>
Cc: Eric Dumazet <eduma...@google.com>
Cc: Jakub Kicinski <k...@kernel.org>
Cc: Paolo Abeni <pab...@redhat.com>
Cc: net...@vger.kernel.org
Link: 
https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci
 [1]
Signed-off-by: Kees Cook <keesc...@chromium.org>
---
 include/net/nexthop.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/net/nexthop.h b/include/net/nexthop.h
index 5dc4b4bba8a5..09f9a732e640 100644
--- a/include/net/nexthop.h
+++ b/include/net/nexthop.h
@@ -92,7 +92,7 @@ struct nh_res_table {
        u32                     unbalanced_timer;
 
        u16                     num_nh_buckets;
-       struct nh_res_bucket    nh_buckets[];
+       struct nh_res_bucket    nh_buckets[] __counted_by(num_nh_buckets);
 };
 
 struct nh_grp_entry {
-- 
2.34.1


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