misc: fastrpc: Safekeep mmaps on interrupted invoke

If the userspace daemon is killed in the middle of an invoke (e.g.
audiopd listerner invoke), we need to skip the unmapping on device
release, otherwise the DSP will crash. So lets safekeep all the maps
only if there is in invoke interrupted, by attaching them to the channel
context (which is resident until RPMSG driver is removed), and free them
on RPMSG driver remove.
Signed-off-by: Abel Vesa <abel.vesa@linaro.org>
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Link: https://lore.kernel.org/r/20221125071405.148786-9-srinivas.kandagatla@linaro.orgSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/misc/fastrpc.c

@@ -275,6 +275,7 @@ struct fastrpc_channel_ctx {
 	struct fastrpc_device *secure_fdevice;
 	struct fastrpc_device *fdevice;
 	struct fastrpc_buf *remote_heap;
+	struct list_head invoke_interrupted_mmaps;
 	bool secure;
 	bool unsigned_support;
 };
@@ -1109,6 +1110,8 @@ static int fastrpc_internal_invoke(struct fastrpc_user *fl,  u32 kernel,
 				   struct fastrpc_invoke_args *args)
 {
 	struct fastrpc_invoke_ctx *ctx = NULL;
+	struct fastrpc_buf *buf, *b;
+
 	int err = 0;
 
 	if (!fl->sctx)
@@ -1172,6 +1175,13 @@ static int fastrpc_internal_invoke(struct fastrpc_user *fl,  u32 kernel,
 		fastrpc_context_put(ctx);
 	}
 
+	if (err == -ERESTARTSYS) {
+		list_for_each_entry_safe(buf, b, &fl->mmaps, node) {
+			list_del(&buf->node);
+			list_add_tail(&buf->node, &fl->cctx->invoke_interrupted_mmaps);
+		}
+	}
+
 	if (err)
 		dev_dbg(fl->sctx->dev, "Error: Invoke Failed %d\n", err);
 
@@ -2278,6 +2288,7 @@ static int fastrpc_rpmsg_probe(struct rpmsg_device *rpdev)
 	dev_set_drvdata(&rpdev->dev, data);
 	dma_set_mask_and_coherent(rdev, DMA_BIT_MASK(32));
 	INIT_LIST_HEAD(&data->users);
+	INIT_LIST_HEAD(&data->invoke_interrupted_mmaps);
 	spin_lock_init(&data->lock);
 	idr_init(&data->ctx_idr);
 	data->domain_id = domain_id;
@@ -2302,6 +2313,7 @@ static void fastrpc_notify_users(struct fastrpc_user *user)
 static void fastrpc_rpmsg_remove(struct rpmsg_device *rpdev)
 {
 	struct fastrpc_channel_ctx *cctx = dev_get_drvdata(&rpdev->dev);
+	struct fastrpc_buf *buf, *b;
 	struct fastrpc_user *user;
 	unsigned long flags;
 
@@ -2316,6 +2328,9 @@ static void fastrpc_rpmsg_remove(struct rpmsg_device *rpdev)
 	if (cctx->secure_fdevice)
 		misc_deregister(&cctx->secure_fdevice->miscdev);
 
+	list_for_each_entry_safe(buf, b, &cctx->invoke_interrupted_mmaps, node)
+		list_del(&buf->node);
+
 	if (cctx->remote_heap)
 		fastrpc_buf_free(cctx->remote_heap);