[PATCH v2 12/12] test: dm: virtio_rng: Test virtio-rng with faked device

[Andrew Scull <ascull@google.com>]

Add a regression test for virtio-rng reading beyond the end of its
buffer if the virtio device provides an invalid length.

Signed-off-by: Andrew Scull <ascull@google.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
---
 test/dm/Makefile     |  1 +
 test/dm/virtio_rng.c | 52 ++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 53 insertions(+)
 create mode 100644 test/dm/virtio_rng.c

diff --git a/test/dm/Makefile b/test/dm/Makefile
index 6c467b145e..ba08c19515 100644
--- a/test/dm/Makefile
+++ b/test/dm/Makefile
@@ -109,6 +109,7 @@ obj-$(CONFIG_DM_VIDEO) += video.o
 ifeq ($(CONFIG_VIRTIO_SANDBOX),y)
 obj-y += virtio.o
 obj-$(CONFIG_VIRTIO_RNG) += virtio_device.o
+obj-$(CONFIG_VIRTIO_RNG) += virtio_rng.o
 endif
 ifeq ($(CONFIG_WDT_GPIO)$(CONFIG_WDT_SANDBOX),yy)
 obj-y += wdt.o
diff --git a/test/dm/virtio_rng.c b/test/dm/virtio_rng.c
new file mode 100644
index 0000000000..ff5646b4e1
--- /dev/null
+++ b/test/dm/virtio_rng.c
@@ -0,0 +1,52 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (c) 2022 Google, Inc.
+ * Written by Andrew Scull <ascull@google.com>
+ */
+
+#include <common.h>
+#include <dm.h>
+#include <virtio_types.h>
+#include <virtio.h>
+#include <virtio_ring.h>
+#include <dm/device-internal.h>
+#include <dm/test.h>
+#include <rng.h>
+#include <test/test.h>
+#include <test/ut.h>
+
+/* This is a brittle means of getting access to the virtqueue */
+struct virtio_rng_priv {
+	struct virtqueue *rng_vq;
+};
+
+/* Test the virtio-rng driver validates the used size */
+static int dm_test_virtio_rng_check_len(struct unit_test_state *uts)
+{
+	struct udevice *bus, *dev;
+	struct virtio_rng_priv *priv;
+	u8 buffer[16];
+
+	/* check probe success */
+	ut_assertok(uclass_first_device(UCLASS_VIRTIO, &bus));
+	ut_assertnonnull(bus);
+
+	/* check the child virtio-rng device is bound */
+	ut_assertok(device_find_first_child(bus, &dev));
+	ut_assertnonnull(dev);
+
+	/* probe the virtio-rng driver */
+	ut_assertok(device_probe(dev));
+
+	/* simulate the device returning the buffer with too much data */
+	priv = dev_get_priv(dev);
+	priv->rng_vq->vring.used->idx = 1;
+	priv->rng_vq->vring.used->ring[0].id = 0;
+	priv->rng_vq->vring.used->ring[0].len = U32_MAX;
+
+	/* check the driver gracefully handles the error */
+	ut_asserteq(-EIO, dm_rng_read(dev, buffer, sizeof(buffer)));
+
+	return 0;
+}
+DM_TEST(dm_test_virtio_rng_check_len, UT_TESTF_SCAN_PDATA | UT_TESTF_SCAN_FDT);
-- 
2.35.1.1178.g4f1659d476-goog