[PATCH v3 for-next 1/3] net: copy from user before calling __copy_msghdr

[Dylan Yudaken <dylany@fb.com>]

this is in preparation for multishot receive from io_uring, where it needs
to have access to the original struct user_msghdr.

functionally this should be a no-op.

Acked-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Dylan Yudaken <dylany@fb.com>
---
 include/linux/socket.h |  7 +++----
 io_uring/net.c         | 17 +++++++++--------
 net/socket.c           | 37 ++++++++++++++++---------------------
 3 files changed, 28 insertions(+), 33 deletions(-)

diff --git a/include/linux/socket.h b/include/linux/socket.h
index 17311ad9f9af..be24f1c8568a 100644
--- a/include/linux/socket.h
+++ b/include/linux/socket.h
@@ -416,10 +416,9 @@ extern int recvmsg_copy_msghdr(struct msghdr *msg,
 			       struct user_msghdr __user *umsg, unsigned flags,
 			       struct sockaddr __user **uaddr,
 			       struct iovec **iov);
-extern int __copy_msghdr_from_user(struct msghdr *kmsg,
-				   struct user_msghdr __user *umsg,
-				   struct sockaddr __user **save_addr,
-				   struct iovec __user **uiov, size_t *nsegs);
+extern int __copy_msghdr(struct msghdr *kmsg,
+			 struct user_msghdr *umsg,
+			 struct sockaddr __user **save_addr);
 
 /* helpers which do the actual work for syscalls */
 extern int __sys_recvfrom(int fd, void __user *ubuf, size_t size,
diff --git a/io_uring/net.c b/io_uring/net.c
index dc9190eafbe7..da7667ed3610 100644
--- a/io_uring/net.c
+++ b/io_uring/net.c
@@ -329,31 +329,32 @@ static int __io_recvmsg_copy_hdr(struct io_kiocb *req,
 				 struct io_async_msghdr *iomsg)
 {
 	struct io_sr_msg *sr = io_kiocb_to_cmd(req);
-	struct iovec __user *uiov;
-	size_t iov_len;
+	struct user_msghdr msg;
 	int ret;
 
-	ret = __copy_msghdr_from_user(&iomsg->msg, sr->umsg,
-					&iomsg->uaddr, &uiov, &iov_len);
+	if (copy_from_user(&msg, sr->umsg, sizeof(*sr->umsg)))
+		return -EFAULT;
+
+	ret = __copy_msghdr(&iomsg->msg, &msg, &iomsg->uaddr);
 	if (ret)
 		return ret;
 
 	if (req->flags & REQ_F_BUFFER_SELECT) {
-		if (iov_len == 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 (iov_len > 1) {
+		} else if (msg.msg_iovlen > 1) {
 			return -EINVAL;
 		} else {
-			if (copy_from_user(iomsg->fast_iov, uiov, sizeof(*uiov)))
+			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;
 		}
 	} else {
 		iomsg->free_iov = iomsg->fast_iov;
-		ret = __import_iovec(READ, uiov, iov_len, UIO_FASTIOV,
+		ret = __import_iovec(READ, msg.msg_iov, msg.msg_iovlen, UIO_FASTIOV,
 				     &iomsg->free_iov, &iomsg->msg.msg_iter,
 				     false);
 		if (ret > 0)
diff --git a/net/socket.c b/net/socket.c
index 96300cdc0625..843545c21ec2 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -2358,25 +2358,20 @@ struct used_address {
 	unsigned int name_len;
 };
 
-int __copy_msghdr_from_user(struct msghdr *kmsg,
-			    struct user_msghdr __user *umsg,
-			    struct sockaddr __user **save_addr,
-			    struct iovec __user **uiov, size_t *nsegs)
+int __copy_msghdr(struct msghdr *kmsg,
+		  struct user_msghdr *msg,
+		  struct sockaddr __user **save_addr)
 {
-	struct user_msghdr msg;
 	ssize_t err;
 
-	if (copy_from_user(&msg, umsg, sizeof(*umsg)))
-		return -EFAULT;
-
 	kmsg->msg_control_is_user = true;
 	kmsg->msg_get_inq = 0;
-	kmsg->msg_control_user = msg.msg_control;
-	kmsg->msg_controllen = msg.msg_controllen;
-	kmsg->msg_flags = msg.msg_flags;
+	kmsg->msg_control_user = msg->msg_control;
+	kmsg->msg_controllen = msg->msg_controllen;
+	kmsg->msg_flags = msg->msg_flags;
 
-	kmsg->msg_namelen = msg.msg_namelen;
-	if (!msg.msg_name)
+	kmsg->msg_namelen = msg->msg_namelen;
+	if (!msg->msg_name)
 		kmsg->msg_namelen = 0;
 
 	if (kmsg->msg_namelen < 0)
@@ -2386,11 +2381,11 @@ int __copy_msghdr_from_user(struct msghdr *kmsg,
 		kmsg->msg_namelen = sizeof(struct sockaddr_storage);
 
 	if (save_addr)
-		*save_addr = msg.msg_name;
+		*save_addr = msg->msg_name;
 
-	if (msg.msg_name && kmsg->msg_namelen) {
+	if (msg->msg_name && kmsg->msg_namelen) {
 		if (!save_addr) {
-			err = move_addr_to_kernel(msg.msg_name,
+			err = move_addr_to_kernel(msg->msg_name,
 						  kmsg->msg_namelen,
 						  kmsg->msg_name);
 			if (err < 0)
@@ -2401,12 +2396,10 @@ int __copy_msghdr_from_user(struct msghdr *kmsg,
 		kmsg->msg_namelen = 0;
 	}
 
-	if (msg.msg_iovlen > UIO_MAXIOV)
+	if (msg->msg_iovlen > UIO_MAXIOV)
 		return -EMSGSIZE;
 
 	kmsg->msg_iocb = NULL;
-	*uiov = msg.msg_iov;
-	*nsegs = msg.msg_iovlen;
 	return 0;
 }
 
@@ -2418,8 +2411,10 @@ static int copy_msghdr_from_user(struct msghdr *kmsg,
 	struct user_msghdr msg;
 	ssize_t err;
 
-	err = __copy_msghdr_from_user(kmsg, umsg, save_addr, &msg.msg_iov,
-					&msg.msg_iovlen);
+	if (copy_from_user(&msg, umsg, sizeof(*umsg)))
+		return -EFAULT;
+
+	err = __copy_msghdr(kmsg, &msg, save_addr);
 	if (err)
 		return err;
 
-- 
2.30.2