io_uring/net: move receive multishot out of the generic msghdr path

Move the actual user_msghdr / compat_msghdr into the send and receive
sides, respectively, so we can move the uaddr receive handling into its
own handler, and ditto the multishot with buffer selection logic.
Signed-off-by: Jens Axboe <axboe@kernel.dk>

io_uring/net.c

@@ -204,46 +204,26 @@ static int io_setup_async_msg(struct io_kiocb *req,
 	return -EAGAIN;
 }
 
-static bool io_recvmsg_multishot_overflow(struct io_async_msghdr *iomsg)
-{
-	int hdr;
-
-	if (iomsg->namelen < 0)
-		return true;
-	if (check_add_overflow((int)sizeof(struct io_uring_recvmsg_out),
-			       iomsg->namelen, &hdr))
-		return true;
-	if (check_add_overflow(hdr, (int)iomsg->controllen, &hdr))
-		return true;
-
-	return false;
-}
-
 #ifdef CONFIG_COMPAT
-static int __io_compat_msg_copy_hdr(struct io_kiocb *req,
-				    struct io_async_msghdr *iomsg,
-				    struct sockaddr __user **addr, int ddir)
+static int io_compat_msg_copy_hdr(struct io_kiocb *req,
+				  struct io_async_msghdr *iomsg,
+				  struct compat_msghdr *msg, int ddir)
 {
 	struct io_sr_msg *sr = io_kiocb_to_cmd(req, struct io_sr_msg);
-	struct compat_msghdr msg;
 	struct compat_iovec __user *uiov;
 	int ret;
 
-	if (copy_from_user(&msg, sr->umsg_compat, sizeof(msg)))
+	if (copy_from_user(msg, sr->umsg_compat, sizeof(*msg)))
 		return -EFAULT;
 
-	ret = __get_compat_msghdr(&iomsg->msg, &msg, addr);
-	if (ret)
-		return ret;
-
-	uiov = compat_ptr(msg.msg_iov);
+	uiov = compat_ptr(msg->msg_iov);
 	if (req->flags & REQ_F_BUFFER_SELECT) {
 		compat_ssize_t clen;
 
 		iomsg->free_iov = NULL;
-		if (msg.msg_iovlen == 0) {
+		if (msg->msg_iovlen == 0) {
 			sr->len = 0;
-		} else if (msg.msg_iovlen > 1) {
+		} else if (msg->msg_iovlen > 1) {
 			return -EINVAL;
 		} else {
 			if (!access_ok(uiov, sizeof(*uiov)))
@@ -255,18 +235,11 @@ static int __io_compat_msg_copy_hdr(struct io_kiocb *req,
 			sr->len = clen;
 		}
 
-		if (ddir == ITER_DEST && req->flags & REQ_F_APOLL_MULTISHOT) {
-			iomsg->namelen = msg.msg_namelen;
-			iomsg->controllen = msg.msg_controllen;
-			if (io_recvmsg_multishot_overflow(iomsg))
-				return -EOVERFLOW;
-		}
-
 		return 0;
 	}
 
 	iomsg->free_iov = iomsg->fast_iov;
-	ret = __import_iovec(ddir, (struct iovec __user *)uiov, msg.msg_iovlen,
+	ret = __import_iovec(ddir, (struct iovec __user *)uiov, msg->msg_iovlen,
 				UIO_FASTIOV, &iomsg->free_iov,
 				&iomsg->msg.msg_iter, true);
 	if (unlikely(ret < 0))
@@ -276,47 +249,35 @@ static int __io_compat_msg_copy_hdr(struct io_kiocb *req,
 }
 #endif
 
-static int __io_msg_copy_hdr(struct io_kiocb *req, struct io_async_msghdr *iomsg,
-			     struct sockaddr __user **addr, int ddir)
+static int io_msg_copy_hdr(struct io_kiocb *req, struct io_async_msghdr *iomsg,
+			   struct user_msghdr *msg, int ddir)
 {
 	struct io_sr_msg *sr = io_kiocb_to_cmd(req, struct io_sr_msg);
-	struct user_msghdr msg;
 	int ret;
 
-	if (copy_from_user(&msg, sr->umsg, sizeof(*sr->umsg)))
+	if (copy_from_user(msg, sr->umsg, sizeof(*sr->umsg)))
 		return -EFAULT;
 
-	ret = __copy_msghdr(&iomsg->msg, &msg, addr);
-	if (ret)
-		return ret;
-
 	if (req->flags & REQ_F_BUFFER_SELECT) {
-		if (msg.msg_iovlen == 0) {
+		if (msg->msg_iovlen == 0) {
 			sr->len = iomsg->fast_iov[0].iov_len = 0;
 			iomsg->fast_iov[0].iov_base = NULL;
 			iomsg->free_iov = NULL;
-		} else if (msg.msg_iovlen > 1) {
+		} else if (msg->msg_iovlen > 1) {
 			return -EINVAL;
 		} else {
-			if (copy_from_user(iomsg->fast_iov, msg.msg_iov,
-					   sizeof(*msg.msg_iov)))
+			if (copy_from_user(iomsg->fast_iov, msg->msg_iov,
+					   sizeof(*msg->msg_iov)))
 				return -EFAULT;
 			sr->len = iomsg->fast_iov[0].iov_len;
 			iomsg->free_iov = NULL;
 		}
 
-		if (ddir == ITER_DEST && req->flags & REQ_F_APOLL_MULTISHOT) {
-			iomsg->namelen = msg.msg_namelen;
-			iomsg->controllen = msg.msg_controllen;
-			if (io_recvmsg_multishot_overflow(iomsg))
-				return -EOVERFLOW;
-		}
-
 		return 0;
 	}
 
 	iomsg->free_iov = iomsg->fast_iov;
-	ret = __import_iovec(ddir, msg.msg_iov, msg.msg_iovlen, UIO_FASTIOV,
+	ret = __import_iovec(ddir, msg->msg_iov, msg->msg_iovlen, UIO_FASTIOV,
 				&iomsg->free_iov, &iomsg->msg.msg_iter, false);
 	if (unlikely(ret < 0))
 		return ret;
@@ -324,30 +285,34 @@ static int __io_msg_copy_hdr(struct io_kiocb *req, struct io_async_msghdr *iomsg
 	return 0;
 }
 
-static int io_msg_copy_hdr(struct io_kiocb *req, struct io_async_msghdr *iomsg,
-			   struct sockaddr __user **addr, int ddir)
+static int io_sendmsg_copy_hdr(struct io_kiocb *req,
+			       struct io_async_msghdr *iomsg)
 {
+	struct io_sr_msg *sr = io_kiocb_to_cmd(req, struct io_sr_msg);
+	struct user_msghdr msg;
+	int ret;
+
 	iomsg->msg.msg_name = &iomsg->addr;
 	iomsg->msg.msg_iter.nr_segs = 0;
 
 #ifdef CONFIG_COMPAT
-	if (req->ctx->compat)
-		return __io_compat_msg_copy_hdr(req, iomsg, addr, ddir);
-#endif
+	if (unlikely(req->ctx->compat)) {
+		struct compat_msghdr cmsg;
 
-	return __io_msg_copy_hdr(req, iomsg, addr, ddir);
-}
+		ret = io_compat_msg_copy_hdr(req, iomsg, &cmsg, ITER_SOURCE);
+		if (unlikely(ret))
+			return ret;
 
-static int io_sendmsg_copy_hdr(struct io_kiocb *req,
-			       struct io_async_msghdr *iomsg)
-{
-	struct io_sr_msg *sr = io_kiocb_to_cmd(req, struct io_sr_msg);
-	int ret;
+		return __get_compat_msghdr(&iomsg->msg, &cmsg, NULL);
+	}
+#endif
 
-	ret = io_msg_copy_hdr(req, iomsg, NULL, ITER_SOURCE);
-	if (ret)
+	ret = io_msg_copy_hdr(req, iomsg, &msg, ITER_SOURCE);
+	if (unlikely(ret))
 		return ret;
 
+	ret = __copy_msghdr(&iomsg->msg, &msg, NULL);
+
 	/* save msg_control as sys_sendmsg() overwrites it */
 	sr->msg_control = iomsg->msg.msg_control_user;
 	return ret;
@@ -569,10 +534,66 @@ int io_send(struct io_kiocb *req, unsigned int issue_flags)
 	return IOU_OK;
 }
 
+static int io_recvmsg_mshot_prep(struct io_kiocb *req,
+				 struct io_async_msghdr *iomsg,
+				 size_t namelen, size_t controllen)
+{
+	if ((req->flags & (REQ_F_APOLL_MULTISHOT|REQ_F_BUFFER_SELECT)) ==
+			  (REQ_F_APOLL_MULTISHOT|REQ_F_BUFFER_SELECT)) {
+		int hdr;
+
+		if (unlikely(namelen < 0))
+			return -EOVERFLOW;
+		if (check_add_overflow((int)sizeof(struct io_uring_recvmsg_out),
+					namelen, &hdr))
+			return -EOVERFLOW;
+		if (check_add_overflow(hdr, (int)controllen, &hdr))
+			return -EOVERFLOW;
+
+		iomsg->namelen = namelen;
+		iomsg->controllen = controllen;
+		return 0;
+	}
+
+	return 0;
+}
+
 static int io_recvmsg_copy_hdr(struct io_kiocb *req,
 			       struct io_async_msghdr *iomsg)
 {
-	return io_msg_copy_hdr(req, iomsg, &iomsg->uaddr, ITER_DEST);
+	struct user_msghdr msg;
+	int ret;
+
+	iomsg->msg.msg_name = &iomsg->addr;
+	iomsg->msg.msg_iter.nr_segs = 0;
+
+#ifdef CONFIG_COMPAT
+	if (unlikely(req->ctx->compat)) {
+		struct compat_msghdr cmsg;
+
+		ret = io_compat_msg_copy_hdr(req, iomsg, &cmsg, ITER_DEST);
+		if (unlikely(ret))
+			return ret;
+
+		ret = __get_compat_msghdr(&iomsg->msg, &cmsg, &iomsg->uaddr);
+		if (unlikely(ret))
+			return ret;
+
+		return io_recvmsg_mshot_prep(req, iomsg, cmsg.msg_namelen,
+						cmsg.msg_controllen);
+	}
+#endif
+
+	ret = io_msg_copy_hdr(req, iomsg, &msg, ITER_DEST);
+	if (unlikely(ret))
+		return ret;
+
+	ret = __copy_msghdr(&iomsg->msg, &msg, &iomsg->uaddr);
+	if (unlikely(ret))
+		return ret;
+
+	return io_recvmsg_mshot_prep(req, iomsg, msg.msg_namelen,
+					msg.msg_controllen);
 }
 
 int io_recvmsg_prep_async(struct io_kiocb *req)