thunderbolt: Fix NULL dereference in tb_remove_work()grafted

There is a slight race between tb_remove_work() and tb_domain_remove()
which leads to dereferencing a NULL tb->root_switch pointer inside
tb_free_unplugged_xdomains():

        Thread A                            Thread B

  tb_remove_work()
                                    tb_domain_remove()
                                      mutex_lock(&tb->lock)
                                      tb_stop()
                                        /* doesn't cancel a running callback */
                                        cancel_delayed_work(&tcm->remove_work)
                                        ...
                                        tb_switch_remove(tb->root_switch)
                                        tb->root_switch = NULL
                                      mutex_unlock(&tb->lock)
    mutex_lock(&tb->lock)
    ...
    /* without checking ->root_switch */
    tb_free_unplugged_xdomains(tb->root_switch)
    mutex_unlock(&tb->lock)

Commit a8937f35cf39 ("thunderbolt: Remove XDomain from the bus without
holding tb->lock") doesn't seem right to move tb_free_unplugged_xdomains()
out of the &tb->lock section and the check for tb->root_switch, in
particular.  It states:

  For this reason separate removing the XDomain from the topology data
  structures (where we need the lock) from unregistering the device from
  the bus (where remove callbacks of the drivers are being called).

tb_free_unplugged_xdomains() belongs to the former group of functions
requiring the lock.  And it also calls tb_xdomain_remove() which should
only be called with &tb->lock held.

Found by Linux Verification Center (linuxtesting.org) with Svace static
analysis tool.

Fixes: a8937f35cf39 ("thunderbolt: Remove XDomain from the bus without holding tb->lock")
Cc: stable@vger.kernel.org
Signed-off-by: Fedor Pchelkin <pchelkin@ispras.ru>
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>

1 files changed, 190 insertions, 0 deletions

diff --git a/drivers/usb/misc/ehset.c b/drivers/usb/misc/ehset.c
new file mode 100644
index 000000000..36b6e9fa7
--- /dev/null
+++ b/drivers/usb/misc/ehset.c
@@ -0,0 +1,190 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2010-2013, The Linux Foundation. All rights reserved.
+ */
+
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/usb.h>
+#include <linux/usb/ch11.h>
+
+#define TEST_SE0_NAK_PID			0x0101
+#define TEST_J_PID				0x0102
+#define TEST_K_PID				0x0103
+#define TEST_PACKET_PID				0x0104
+#define TEST_HS_HOST_PORT_SUSPEND_RESUME	0x0106
+#define TEST_SINGLE_STEP_GET_DEV_DESC		0x0107
+#define TEST_SINGLE_STEP_SET_FEATURE		0x0108
+
+extern const struct usb_device_id *usb_device_match_id(struct usb_device *udev,
+						const struct usb_device_id *id);
+
+/*
+ * A list of USB hubs which requires to disable the power
+ * to the port before starting the testing procedures.
+ */
+static const struct usb_device_id ehset_hub_list[] = {
+	{ USB_DEVICE(0x0424, 0x4502) },
+	{ USB_DEVICE(0x0424, 0x4913) },
+	{ USB_DEVICE(0x0451, 0x8027) },
+	{ }
+};
+
+static int ehset_prepare_port_for_testing(struct usb_device *hub_udev, u16 portnum)
+{
+	int ret = 0;
+
+	/*
+	 * The USB2.0 spec chapter 11.24.2.13 says that the USB port which is
+	 * going under test needs to be put in suspend before sending the
+	 * test command. Most hubs don't enforce this precondition, but there
+	 * are some hubs which needs to disable the power to the port before
+	 * starting the test.
+	 */
+	if (usb_device_match_id(hub_udev, ehset_hub_list)) {
+		ret = usb_control_msg_send(hub_udev, 0, USB_REQ_CLEAR_FEATURE,
+					   USB_RT_PORT, USB_PORT_FEAT_ENABLE,
+					   portnum, NULL, 0, 1000, GFP_KERNEL);
+		/*
+		 * Wait for the port to be disabled. It's an arbitrary value
+		 * which worked every time.
+		 */
+		msleep(100);
+	} else {
+		/*
+		 * For the hubs which are compliant with the spec,
+		 * put the port in SUSPEND.
+		 */
+		ret = usb_control_msg_send(hub_udev, 0, USB_REQ_SET_FEATURE,
+					   USB_RT_PORT, USB_PORT_FEAT_SUSPEND,
+					   portnum, NULL, 0, 1000, GFP_KERNEL);
+	}
+	return ret;
+}
+
+static int ehset_probe(struct usb_interface *intf,
+		       const struct usb_device_id *id)
+{
+	int ret = -EINVAL;
+	struct usb_device *dev = interface_to_usbdev(intf);
+	struct usb_device *hub_udev = dev->parent;
+	struct usb_device_descriptor buf;
+	u8 portnum = dev->portnum;
+	u16 test_pid = le16_to_cpu(dev->descriptor.idProduct);
+
+	switch (test_pid) {
+	case TEST_SE0_NAK_PID:
+		ret = ehset_prepare_port_for_testing(hub_udev, portnum);
+		if (ret < 0)
+			break;
+		ret = usb_control_msg_send(hub_udev, 0, USB_REQ_SET_FEATURE,
+					   USB_RT_PORT, USB_PORT_FEAT_TEST,
+					   (USB_TEST_SE0_NAK << 8) | portnum,
+					   NULL, 0, 1000, GFP_KERNEL);
+		break;
+	case TEST_J_PID:
+		ret = ehset_prepare_port_for_testing(hub_udev, portnum);
+		if (ret < 0)
+			break;
+		ret = usb_control_msg_send(hub_udev, 0, USB_REQ_SET_FEATURE,
+					   USB_RT_PORT, USB_PORT_FEAT_TEST,
+					   (USB_TEST_J << 8) | portnum, NULL, 0,
+					   1000, GFP_KERNEL);
+		break;
+	case TEST_K_PID:
+		ret = ehset_prepare_port_for_testing(hub_udev, portnum);
+		if (ret < 0)
+			break;
+		ret = usb_control_msg_send(hub_udev, 0, USB_REQ_SET_FEATURE,
+					   USB_RT_PORT, USB_PORT_FEAT_TEST,
+					   (USB_TEST_K << 8) | portnum, NULL, 0,
+					   1000, GFP_KERNEL);
+		break;
+	case TEST_PACKET_PID:
+		ret = ehset_prepare_port_for_testing(hub_udev, portnum);
+		if (ret < 0)
+			break;
+		ret = usb_control_msg_send(hub_udev, 0, USB_REQ_SET_FEATURE,
+					   USB_RT_PORT, USB_PORT_FEAT_TEST,
+					   (USB_TEST_PACKET << 8) | portnum,
+					   NULL, 0, 1000, GFP_KERNEL);
+		break;
+	case TEST_HS_HOST_PORT_SUSPEND_RESUME:
+		/* Test: wait for 15secs -> suspend -> 15secs delay -> resume */
+		msleep(15 * 1000);
+		ret = usb_control_msg_send(hub_udev, 0, USB_REQ_SET_FEATURE,
+					   USB_RT_PORT, USB_PORT_FEAT_SUSPEND,
+					   portnum, NULL, 0, 1000, GFP_KERNEL);
+		if (ret < 0)
+			break;
+
+		msleep(15 * 1000);
+		ret = usb_control_msg_send(hub_udev, 0, USB_REQ_CLEAR_FEATURE,
+					   USB_RT_PORT, USB_PORT_FEAT_SUSPEND,
+					   portnum, NULL, 0, 1000, GFP_KERNEL);
+		break;
+	case TEST_SINGLE_STEP_GET_DEV_DESC:
+		/* Test: wait for 15secs -> GetDescriptor request */
+		msleep(15 * 1000);
+
+		ret = usb_control_msg_recv(dev, 0, USB_REQ_GET_DESCRIPTOR,
+					   USB_DIR_IN, USB_DT_DEVICE << 8, 0,
+					   &buf, USB_DT_DEVICE_SIZE,
+					   USB_CTRL_GET_TIMEOUT, GFP_KERNEL);
+		break;
+	case TEST_SINGLE_STEP_SET_FEATURE:
+		/*
+		 * GetDescriptor SETUP request -> 15secs delay -> IN & STATUS
+		 *
+		 * Note, this test is only supported on root hubs since the
+		 * SetPortFeature handling can only be done inside the HCD's
+		 * hub_control callback function.
+		 */
+		if (hub_udev != dev->bus->root_hub) {
+			dev_err(&intf->dev, "SINGLE_STEP_SET_FEATURE test only supported on root hub\n");
+			break;
+		}
+
+		ret = usb_control_msg_send(hub_udev, 0, USB_REQ_SET_FEATURE,
+					   USB_RT_PORT, USB_PORT_FEAT_TEST,
+					   (6 << 8) | portnum, NULL, 0,
+					   60 * 1000, GFP_KERNEL);
+
+		break;
+	default:
+		dev_err(&intf->dev, "%s: unsupported PID: 0x%x\n",
+			__func__, test_pid);
+	}
+
+	return ret;
+}
+
+static void ehset_disconnect(struct usb_interface *intf)
+{
+}
+
+static const struct usb_device_id ehset_id_table[] = {
+	{ USB_DEVICE(0x1a0a, TEST_SE0_NAK_PID) },
+	{ USB_DEVICE(0x1a0a, TEST_J_PID) },
+	{ USB_DEVICE(0x1a0a, TEST_K_PID) },
+	{ USB_DEVICE(0x1a0a, TEST_PACKET_PID) },
+	{ USB_DEVICE(0x1a0a, TEST_HS_HOST_PORT_SUSPEND_RESUME) },
+	{ USB_DEVICE(0x1a0a, TEST_SINGLE_STEP_GET_DEV_DESC) },
+	{ USB_DEVICE(0x1a0a, TEST_SINGLE_STEP_SET_FEATURE) },
+	{ }			/* Terminating entry */
+};
+MODULE_DEVICE_TABLE(usb, ehset_id_table);
+
+static struct usb_driver ehset_driver = {
+	.name =		"usb_ehset_test",
+	.probe =	ehset_probe,
+	.disconnect =	ehset_disconnect,
+	.id_table =	ehset_id_table,
+};
+
+module_usb_driver(ehset_driver);
+
+MODULE_DESCRIPTION("USB Driver for EHSET Test Fixture");
+MODULE_LICENSE("GPL v2");