io_uring: check reserved fields for recv/recvmsg

We should check unused fields for non-zero and -EINVAL if they are set,
making it consistent with other opcodes.

Fixes: aa1fa28 ("io_uring: add support for recvmsg()")
Signed-off-by: Jens Axboe <axboe@kernel.dk>

fs/io_uring.c

@@ -5420,6 +5420,8 @@ static int io_recvmsg_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
 
 	if (unlikely(req->ctx->flags & IORING_SETUP_IOPOLL))
 		return -EINVAL;
+	if (unlikely(sqe->addr2 || sqe->file_index))
+		return -EINVAL;
 
 	sr->umsg = u64_to_user_ptr(READ_ONCE(sqe->addr));
 	sr->len = READ_ONCE(sqe->len);