net/mlx5: Annotate struct mlx5_flow_handle 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 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 mlx5_flow_handle.

Cc: Saeed Mahameed <[email protected]>
Cc: Leon Romanovsky <[email protected]>
Cc: "David S. Miller" <[email protected]>
Cc: Eric Dumazet <[email protected]>
Cc: Jakub Kicinski <[email protected]>
Cc: Paolo Abeni <[email protected]>
Cc: [email protected]
Cc: [email protected]
Link: https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci [1]
Signed-off-by: Kees Cook <[email protected]>
Reviewed-by: Justin Stitt <[email protected]>
Reviewed-by: Gustavo A. R. Silva <[email protected]>
Reviewed-by: Leon Romanovsky <[email protected]>
Signed-off-by: Saeed Mahameed <[email protected]>

Author: kees

drivers/net/ethernet/mellanox/mlx5/core/fs_core.h

@@ -181,7 +181,7 @@ struct mlx5_flow_rule {
 
 struct mlx5_flow_handle {
 	int num_rules;
-	struct mlx5_flow_rule *rule[];
+	struct mlx5_flow_rule *rule[] __counted_by(num_rules);
 };
 
 /* Type of children is mlx5_flow_group */