[PATCH 4/7] io_uring/net: verify msghdr before copying iovec

[Pavel Begunkov <asml.silence@gmail.com>]

Normally, net/ would verify msghdr before importing iovec, for example
see copy_msghdr_from_user(), which further assumed by __copy_msghdr()
validating msg->msg_iovlen.

io_uring does it in reverse order, which is fine, but it'll be more
convenient for flip it so that the iovec business is done at the end and
eventually can be nicely pulled out of msghdr parsing section and
thought as a sepaarate step. That also makes structure accesses more
localised, which should be better for caches.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---
 io_uring/net.c | 43 ++++++++++++++++++-------------------------
 1 file changed, 18 insertions(+), 25 deletions(-)

diff --git a/io_uring/net.c b/io_uring/net.c
index 67d768e6ecdd..14eeebfd8a5a 100644
--- a/io_uring/net.c
+++ b/io_uring/net.c
@@ -195,7 +195,8 @@ static inline void io_mshot_prep_retry(struct io_kiocb *req,
 #ifdef CONFIG_COMPAT
 static int io_compat_msg_copy_hdr(struct io_kiocb *req,
 				  struct io_async_msghdr *iomsg,
-				  struct compat_msghdr *msg, int ddir)
+				  struct compat_msghdr *msg, int ddir,
+				  struct sockaddr __user **save_addr)
 {
 	struct io_sr_msg *sr = io_kiocb_to_cmd(req, struct io_sr_msg);
 	struct compat_iovec __user *uiov;
@@ -213,6 +214,10 @@ static int io_compat_msg_copy_hdr(struct io_kiocb *req,
 	if (copy_from_user(msg, sr->umsg_compat, sizeof(*msg)))
 		return -EFAULT;
 
+	ret = __get_compat_msghdr(&iomsg->msg, msg, save_addr);
+	if (ret)
+		return ret;
+
 	uiov = compat_ptr(msg->msg_iov);
 	if (req->flags & REQ_F_BUFFER_SELECT) {
 		if (msg->msg_iovlen == 0) {
@@ -262,7 +267,8 @@ static int io_copy_msghdr_from_user(struct user_msghdr *msg,
 }
 
 static int io_msg_copy_hdr(struct io_kiocb *req, struct io_async_msghdr *iomsg,
-			   struct user_msghdr *msg, int ddir)
+			   struct user_msghdr *msg, int ddir,
+			   struct sockaddr __user **save_addr)
 {
 	struct io_sr_msg *sr = io_kiocb_to_cmd(req, struct io_sr_msg);
 	struct user_msghdr __user *umsg = sr->umsg;
@@ -283,6 +289,10 @@ static int io_msg_copy_hdr(struct io_kiocb *req, struct io_async_msghdr *iomsg,
 
 	msg->msg_flags = 0;
 
+	ret = __copy_msghdr(&iomsg->msg, msg, save_addr);
+	if (ret)
+		return ret;
+
 	if (req->flags & REQ_F_BUFFER_SELECT) {
 		if (msg->msg_iovlen == 0) {
 			sr->len = iov->iov_len = 0;
@@ -322,22 +332,14 @@ static int io_sendmsg_copy_hdr(struct io_kiocb *req,
 	if (io_is_compat(req->ctx)) {
 		struct compat_msghdr cmsg;
 
-		ret = io_compat_msg_copy_hdr(req, iomsg, &cmsg, ITER_SOURCE);
-		if (unlikely(ret))
-			return ret;
-
-		ret = __get_compat_msghdr(&iomsg->msg, &cmsg, NULL);
+		ret = io_compat_msg_copy_hdr(req, iomsg, &cmsg, ITER_SOURCE,
+					     NULL);
 		sr->msg_control = iomsg->msg.msg_control_user;
 		return ret;
 	}
 #endif
 
-	ret = io_msg_copy_hdr(req, iomsg, &msg, ITER_SOURCE);
-	if (unlikely(ret))
-		return ret;
-
-	ret = __copy_msghdr(&iomsg->msg, &msg, NULL);
-
+	ret = io_msg_copy_hdr(req, iomsg, &msg, ITER_SOURCE, NULL);
 	/* save msg_control as sys_sendmsg() overwrites it */
 	sr->msg_control = iomsg->msg.msg_control_user;
 	return ret;
@@ -719,27 +721,18 @@ static int io_recvmsg_copy_hdr(struct io_kiocb *req,
 	if (io_is_compat(req->ctx)) {
 		struct compat_msghdr cmsg;
 
-		ret = io_compat_msg_copy_hdr(req, iomsg, &cmsg, ITER_DEST);
+		ret = io_compat_msg_copy_hdr(req, iomsg, &cmsg, ITER_DEST,
+					     &iomsg->uaddr);
 		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);
+	ret = io_msg_copy_hdr(req, iomsg, &msg, ITER_DEST, &iomsg->uaddr);
 	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);
 }
-- 
2.48.1