io_uring: make io_buffer_select() return the user address directly

There's no point in having callers provide a kbuf, we're just returning
the address anyway.
Signed-off-by: Jens Axboe <axboe@kernel.dk>

fs/io_uring.c

@@ -3458,15 +3458,15 @@ static void io_buffer_add_list(struct io_ring_ctx *ctx,
 	list_add(&bl->list, list);
 }
 
-static struct io_buffer *io_buffer_select(struct io_kiocb *req, size_t *len,
-					  int bgid, unsigned int issue_flags)
+static void __user *io_buffer_select(struct io_kiocb *req, size_t *len,
+				     int bgid, unsigned int issue_flags)
 {
 	struct io_buffer *kbuf = req->kbuf;
 	struct io_ring_ctx *ctx = req->ctx;
 	struct io_buffer_list *bl;
 
 	if (req->flags & REQ_F_BUFFER_SELECTED)
-		return kbuf;
+		return u64_to_user_ptr(kbuf->addr);
 
 	io_ring_submit_lock(req->ctx, issue_flags);
 
@@ -3478,25 +3478,18 @@ static struct io_buffer *io_buffer_select(struct io_kiocb *req, size_t *len,
 			*len = kbuf->len;
 		req->flags |= REQ_F_BUFFER_SELECTED;
 		req->kbuf = kbuf;
-	} else {
-		kbuf = ERR_PTR(-ENOBUFS);
+		io_ring_submit_unlock(req->ctx, issue_flags);
+		return u64_to_user_ptr(kbuf->addr);
 	}
 
 	io_ring_submit_unlock(req->ctx, issue_flags);
-	return kbuf;
+	return ERR_PTR(-ENOBUFS);
 }
 
 static void __user *io_rw_buffer_select(struct io_kiocb *req, size_t *len,
 					unsigned int issue_flags)
 {
-	struct io_buffer *kbuf;
-	u16 bgid;
-
-	bgid = req->buf_index;
-	kbuf = io_buffer_select(req, len, bgid, issue_flags);
-	if (IS_ERR(kbuf))
-		return kbuf;
-	return u64_to_user_ptr(kbuf->addr);
+	return io_buffer_select(req, len, req->buf_index, issue_flags);
 }
 
 #ifdef CONFIG_COMPAT
@@ -5535,7 +5528,6 @@ static int io_recvmsg(struct io_kiocb *req, unsigned int issue_flags)
 	struct io_async_msghdr iomsg, *kmsg;
 	struct io_sr_msg *sr = &req->sr_msg;
 	struct socket *sock;
-	struct io_buffer *kbuf;
 	unsigned flags;
 	int ret, min_ret = 0;
 	bool force_nonblock = issue_flags & IO_URING_F_NONBLOCK;
@@ -5558,10 +5550,12 @@ static int io_recvmsg(struct io_kiocb *req, unsigned int issue_flags)
 		return io_setup_async_msg(req, kmsg);
 
 	if (req->flags & REQ_F_BUFFER_SELECT) {
-		kbuf = io_buffer_select(req, &sr->len, sr->bgid, issue_flags);
-		if (IS_ERR(kbuf))
-			return PTR_ERR(kbuf);
-		kmsg->fast_iov[0].iov_base = u64_to_user_ptr(kbuf->addr);
+		void __user *buf;
+
+		buf = io_buffer_select(req, &sr->len, sr->bgid, issue_flags);
+		if (IS_ERR(buf))
+			return PTR_ERR(buf);
+		kmsg->fast_iov[0].iov_base = buf;
 		kmsg->fast_iov[0].iov_len = sr->len;
 		iov_iter_init(&kmsg->msg.msg_iter, READ, kmsg->fast_iov, 1,
 				sr->len);
@@ -5603,10 +5597,8 @@ static int io_recvmsg(struct io_kiocb *req, unsigned int issue_flags)
 
 static int io_recv(struct io_kiocb *req, unsigned int issue_flags)
 {
-	struct io_buffer *kbuf;
 	struct io_sr_msg *sr = &req->sr_msg;
 	struct msghdr msg;
-	void __user *buf = sr->buf;
 	struct socket *sock;
 	struct iovec iov;
 	unsigned flags;
@@ -5622,13 +5614,15 @@ static int io_recv(struct io_kiocb *req, unsigned int issue_flags)
 		return -ENOTSOCK;
 
 	if (req->flags & REQ_F_BUFFER_SELECT) {
-		kbuf = io_buffer_select(req, &sr->len, sr->bgid, issue_flags);
-		if (IS_ERR(kbuf))
-			return PTR_ERR(kbuf);
-		buf = u64_to_user_ptr(kbuf->addr);
+		void __user *buf;
+
+		buf = io_buffer_select(req, &sr->len, sr->bgid, issue_flags);
+		if (IS_ERR(buf))
+			return PTR_ERR(buf);
+		sr->buf = buf;
 	}
 
-	ret = import_single_range(READ, buf, sr->len, &iov, &msg.msg_iter);
+	ret = import_single_range(READ, sr->buf, sr->len, &iov, &msg.msg_iter);
 	if (unlikely(ret))
 		goto out_free;