io_uring/zcrx: check ctrl op payload struct sizes

Add a build check that ctrl payloads are of the same size and don't grow
struct zcrx_ctrl.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://patch.msgid.link/af66caf9776d18e9ff880ab828eb159a6a03caf5.1774261953.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Author: isilence

io_uring/zcrx.c

@@ -1253,6 +1253,8 @@ int io_zcrx_ctrl(struct io_ring_ctx *ctx, void __user *arg, unsigned nr_args)
 	struct zcrx_ctrl ctrl;
 	struct io_zcrx_ifq *zcrx;
 
+	BUILD_BUG_ON(sizeof(ctrl.zc_export) != sizeof(ctrl.zc_flush));
+
 	if (nr_args)
 		return -EINVAL;
 	if (copy_from_user(&ctrl, arg, sizeof(ctrl)))