io_uring/net: use the correct msghdr union member in io_sendmsg_copy_hdr

Rather than assign the user pointer to msghdr->msg_control, assign it
to msghdr->msg_control_user to make sparse happy. They are in a union
so the end result is the same, but let's avoid new sparse warnings and
squash this one.
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202306210654.mDMcyMuB-lkp@intel.com/
Fixes: cac9e441 ("io_uring/net: save msghdr->msg_control for retries")
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

io_uring/net.c

@@ -203,7 +203,7 @@ static int io_sendmsg_copy_hdr(struct io_kiocb *req,
 	ret = sendmsg_copy_msghdr(&iomsg->msg, sr->umsg, sr->msg_flags,
 					&iomsg->free_iov);
 	/* save msg_control as sys_sendmsg() overwrites it */
-	sr->msg_control = iomsg->msg.msg_control;
+	sr->msg_control = iomsg->msg.msg_control_user;
 	return ret;
 }
 
@@ -302,7 +302,7 @@ int io_sendmsg(struct io_kiocb *req, unsigned int issue_flags)
 
 	if (req_has_async_data(req)) {
 		kmsg = req->async_data;
-		kmsg->msg.msg_control = sr->msg_control;
+		kmsg->msg.msg_control_user = sr->msg_control;
 	} else {
 		ret = io_sendmsg_copy_hdr(req, &iomsg);
 		if (ret)