misc: fastrpc: Rework fastrpc_req_munmap

Move the lookup of the munmap request to the fastrpc_req_munmap and pass
on only the buf to the lower level fastrpc_req_munmap_impl. That way
we can use the lower level fastrpc_req_munmap_impl on error path in
fastrpc_req_mmap to free the buf without searching for the munmap
request it belongs to.

Co-developed-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Signed-off-by: Abel Vesa <abel.vesa@linaro.org>
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Link: https://lore.kernel.org/r/20221125071405.148786-7-srinivas.kandagatla@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/misc/fastrpc.c

@@ -1627,30 +1627,14 @@ static int fastrpc_get_dsp_info(struct fastrpc_user *fl, char __user *argp)
 	return 0;
 }
 
-static int fastrpc_req_munmap_impl(struct fastrpc_user *fl,
-				   struct fastrpc_req_munmap *req)
+static int fastrpc_req_munmap_impl(struct fastrpc_user *fl, struct fastrpc_buf *buf)
 {
 	struct fastrpc_invoke_args args[1] = { [0] = { 0 } };
-	struct fastrpc_buf *buf = NULL, *iter, *b;
 	struct fastrpc_munmap_req_msg req_msg;
 	struct device *dev = fl->sctx->dev;
 	int err;
 	u32 sc;
 
-	spin_lock(&fl->lock);
-	list_for_each_entry_safe(iter, b, &fl->mmaps, node) {
-		if ((iter->raddr == req->vaddrout) && (iter->size == req->size)) {
-			buf = iter;
-			break;
-		}
-	}
-	spin_unlock(&fl->lock);
-
-	if (!buf) {
-		dev_err(dev, "mmap not in list\n");
-		return -EINVAL;
-	}
-
 	req_msg.pgid = fl->tgid;
 	req_msg.size = buf->size;
 	req_msg.vaddr = buf->raddr;
@@ -1676,12 +1660,29 @@ static int fastrpc_req_munmap_impl(struct fastrpc_user *fl,
 
 static int fastrpc_req_munmap(struct fastrpc_user *fl, char __user *argp)
 {
+	struct fastrpc_buf *buf = NULL, *iter, *b;
 	struct fastrpc_req_munmap req;
+	struct device *dev = fl->sctx->dev;
 
 	if (copy_from_user(&req, argp, sizeof(req)))
 		return -EFAULT;
 
-	return fastrpc_req_munmap_impl(fl, &req);
+	spin_lock(&fl->lock);
+	list_for_each_entry_safe(iter, b, &fl->mmaps, node) {
+		if ((iter->raddr == req.vaddrout) && (iter->size == req.size)) {
+			buf = iter;
+			break;
+		}
+	}
+	spin_unlock(&fl->lock);
+
+	if (!buf) {
+		dev_err(dev, "mmap\t\tpt 0x%09llx [len 0x%08llx] not in list\n",
+			req.vaddrout, req.size);
+		return -EINVAL;
+	}
+
+	return fastrpc_req_munmap_impl(fl, buf);
 }
 
 static int fastrpc_req_mmap(struct fastrpc_user *fl, char __user *argp)
@@ -1690,7 +1691,6 @@ static int fastrpc_req_mmap(struct fastrpc_user *fl, char __user *argp)
 	struct fastrpc_buf *buf = NULL;
 	struct fastrpc_mmap_req_msg req_msg;
 	struct fastrpc_mmap_rsp_msg rsp_msg;
-	struct fastrpc_req_munmap req_unmap;
 	struct fastrpc_phy_page pages;
 	struct fastrpc_req_mmap req;
 	struct device *dev = fl->sctx->dev;
@@ -1752,18 +1752,17 @@ static int fastrpc_req_mmap(struct fastrpc_user *fl, char __user *argp)
 	spin_unlock(&fl->lock);
 
 	if (copy_to_user((void __user *)argp, &req, sizeof(req))) {
-		/* unmap the memory and release the buffer */
-		req_unmap.vaddrout = buf->raddr;
-		req_unmap.size = buf->size;
-		fastrpc_req_munmap_impl(fl, &req_unmap);
-		return -EFAULT;
+		err = -EFAULT;
+		goto err_assign;
 	}
 
 	dev_dbg(dev, "mmap\t\tpt 0x%09lx OK [len 0x%08llx]\n",
 		buf->raddr, buf->size);
 
 	return 0;
 
+err_assign:
+	fastrpc_req_munmap_impl(fl, buf);
 err_invoke:
 	fastrpc_buf_free(buf);