io_uring: check that data field is 0 in ringfd unregister

Only allow data field to be 0 in struct io_uring_rsrc_update user
arguments to allow for future possible usage.

Fixes: e7a6c00 ("io_uring: add support for registering ring file descriptors")
Signed-off-by: Eugene Syromiatnikov <esyr@redhat.com>
Link: https://lore.kernel.org/r/20220429142218.GA28696@asgard.redhat.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

fs/io_uring.c

@@ -10593,7 +10593,7 @@ static int io_ringfd_unregister(struct io_ring_ctx *ctx, void __user *__arg,
 			ret = -EFAULT;
 			break;
 		}
-		if (reg.resv || reg.offset >= IO_RINGFD_REG_MAX) {
+		if (reg.resv || reg.data || reg.offset >= IO_RINGFD_REG_MAX) {
 			ret = -EINVAL;
 			break;
 		}