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, 319 insertions, 0 deletions

diff --git a/drivers/usb/common/debug.c b/drivers/usb/common/debug.c
new file mode 100644
index 000000000..f204cec8d
--- /dev/null
+++ b/drivers/usb/common/debug.c
@@ -0,0 +1,319 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Common USB debugging functions
+ *
+ * Copyright (C) 2010-2011 Texas Instruments Incorporated - https://www.ti.com
+ *
+ * Authors: Felipe Balbi <balbi@ti.com>,
+ *	    Sebastian Andrzej Siewior <bigeasy@linutronix.de>
+ */
+
+#include <linux/kernel.h>
+#include <linux/usb/ch9.h>
+
+static void usb_decode_get_status(__u8 bRequestType, __u16 wIndex,
+				  __u16 wLength, char *str, size_t size)
+{
+	switch (bRequestType & USB_RECIP_MASK) {
+	case USB_RECIP_DEVICE:
+		snprintf(str, size, "Get Device Status(Length = %d)", wLength);
+		break;
+	case USB_RECIP_INTERFACE:
+		snprintf(str, size,
+			 "Get Interface Status(Intf = %d, Length = %d)",
+			 wIndex, wLength);
+		break;
+	case USB_RECIP_ENDPOINT:
+		snprintf(str, size, "Get Endpoint Status(ep%d%s)",
+			 wIndex & ~USB_DIR_IN,
+			 wIndex & USB_DIR_IN ? "in" : "out");
+		break;
+	}
+}
+
+static const char *usb_decode_device_feature(u16 wValue)
+{
+	switch (wValue) {
+	case USB_DEVICE_SELF_POWERED:
+		return "Self Powered";
+	case USB_DEVICE_REMOTE_WAKEUP:
+		return "Remote Wakeup";
+	case USB_DEVICE_TEST_MODE:
+		return "Test Mode";
+	case USB_DEVICE_U1_ENABLE:
+		return "U1 Enable";
+	case USB_DEVICE_U2_ENABLE:
+		return "U2 Enable";
+	case USB_DEVICE_LTM_ENABLE:
+		return "LTM Enable";
+	default:
+		return "UNKNOWN";
+	}
+}
+
+static const char *usb_decode_test_mode(u16 wIndex)
+{
+	switch (wIndex) {
+	case USB_TEST_J:
+		return ": TEST_J";
+	case USB_TEST_K:
+		return ": TEST_K";
+	case USB_TEST_SE0_NAK:
+		return ": TEST_SE0_NAK";
+	case USB_TEST_PACKET:
+		return ": TEST_PACKET";
+	case USB_TEST_FORCE_ENABLE:
+		return ": TEST_FORCE_EN";
+	default:
+		return ": UNKNOWN";
+	}
+}
+
+static void usb_decode_set_clear_feature(__u8 bRequestType,
+					 __u8 bRequest, __u16 wValue,
+					 __u16 wIndex, char *str, size_t size)
+{
+	switch (bRequestType & USB_RECIP_MASK) {
+	case USB_RECIP_DEVICE:
+		snprintf(str, size, "%s Device Feature(%s%s)",
+			 bRequest == USB_REQ_CLEAR_FEATURE ? "Clear" : "Set",
+			 usb_decode_device_feature(wValue),
+			 wValue == USB_DEVICE_TEST_MODE ?
+			 usb_decode_test_mode(wIndex) : "");
+		break;
+	case USB_RECIP_INTERFACE:
+		snprintf(str, size, "%s Interface Feature(%s)",
+			 bRequest == USB_REQ_CLEAR_FEATURE ? "Clear" : "Set",
+			 wValue == USB_INTRF_FUNC_SUSPEND ?
+			 "Function Suspend" : "UNKNOWN");
+		break;
+	case USB_RECIP_ENDPOINT:
+		snprintf(str, size, "%s Endpoint Feature(%s ep%d%s)",
+			 bRequest == USB_REQ_CLEAR_FEATURE ? "Clear" : "Set",
+			 wValue == USB_ENDPOINT_HALT ? "Halt" : "UNKNOWN",
+			 wIndex & ~USB_DIR_IN,
+			 wIndex & USB_DIR_IN ? "in" : "out");
+		break;
+	}
+}
+
+static void usb_decode_set_address(__u16 wValue, char *str, size_t size)
+{
+	snprintf(str, size, "Set Address(Addr = %02x)", wValue);
+}
+
+static void usb_decode_get_set_descriptor(__u8 bRequestType, __u8 bRequest,
+					  __u16 wValue, __u16 wIndex,
+					  __u16 wLength, char *str, size_t size)
+{
+	char *s;
+
+	switch (wValue >> 8) {
+	case USB_DT_DEVICE:
+		s = "Device";
+		break;
+	case USB_DT_CONFIG:
+		s = "Configuration";
+		break;
+	case USB_DT_STRING:
+		s = "String";
+		break;
+	case USB_DT_INTERFACE:
+		s = "Interface";
+		break;
+	case USB_DT_ENDPOINT:
+		s = "Endpoint";
+		break;
+	case USB_DT_DEVICE_QUALIFIER:
+		s = "Device Qualifier";
+		break;
+	case USB_DT_OTHER_SPEED_CONFIG:
+		s = "Other Speed Config";
+		break;
+	case USB_DT_INTERFACE_POWER:
+		s = "Interface Power";
+		break;
+	case USB_DT_OTG:
+		s = "OTG";
+		break;
+	case USB_DT_DEBUG:
+		s = "Debug";
+		break;
+	case USB_DT_INTERFACE_ASSOCIATION:
+		s = "Interface Association";
+		break;
+	case USB_DT_BOS:
+		s = "BOS";
+		break;
+	case USB_DT_DEVICE_CAPABILITY:
+		s = "Device Capability";
+		break;
+	case USB_DT_PIPE_USAGE:
+		s = "Pipe Usage";
+		break;
+	case USB_DT_SS_ENDPOINT_COMP:
+		s = "SS Endpoint Companion";
+		break;
+	case USB_DT_SSP_ISOC_ENDPOINT_COMP:
+		s = "SSP Isochronous Endpoint Companion";
+		break;
+	default:
+		s = "UNKNOWN";
+		break;
+	}
+
+	snprintf(str, size, "%s %s Descriptor(Index = %d, Length = %d)",
+		bRequest == USB_REQ_GET_DESCRIPTOR ? "Get" : "Set",
+		s, wValue & 0xff, wLength);
+}
+
+static void usb_decode_get_configuration(__u16 wLength, char *str, size_t size)
+{
+	snprintf(str, size, "Get Configuration(Length = %d)", wLength);
+}
+
+static void usb_decode_set_configuration(__u8 wValue, char *str, size_t size)
+{
+	snprintf(str, size, "Set Configuration(Config = %d)", wValue);
+}
+
+static void usb_decode_get_intf(__u16 wIndex, __u16 wLength, char *str,
+				size_t size)
+{
+	snprintf(str, size, "Get Interface(Intf = %d, Length = %d)",
+		 wIndex, wLength);
+}
+
+static void usb_decode_set_intf(__u8 wValue, __u16 wIndex, char *str,
+				size_t size)
+{
+	snprintf(str, size, "Set Interface(Intf = %d, Alt.Setting = %d)",
+		 wIndex, wValue);
+}
+
+static void usb_decode_synch_frame(__u16 wIndex, __u16 wLength,
+				   char *str, size_t size)
+{
+	snprintf(str, size, "Synch Frame(Endpoint = %d, Length = %d)",
+		 wIndex, wLength);
+}
+
+static void usb_decode_set_sel(__u16 wLength, char *str, size_t size)
+{
+	snprintf(str, size, "Set SEL(Length = %d)", wLength);
+}
+
+static void usb_decode_set_isoch_delay(__u8 wValue, char *str, size_t size)
+{
+	snprintf(str, size, "Set Isochronous Delay(Delay = %d ns)", wValue);
+}
+
+static void usb_decode_ctrl_generic(char *str, size_t size, __u8 bRequestType,
+				    __u8 bRequest, __u16 wValue, __u16 wIndex,
+				    __u16 wLength)
+{
+	u8 recip = bRequestType & USB_RECIP_MASK;
+	u8 type = bRequestType & USB_TYPE_MASK;
+
+	snprintf(str, size,
+		 "Type=%s Recipient=%s Dir=%s bRequest=%u wValue=%u wIndex=%u wLength=%u",
+		 (type == USB_TYPE_STANDARD)    ? "Standard" :
+		 (type == USB_TYPE_VENDOR)      ? "Vendor" :
+		 (type == USB_TYPE_CLASS)       ? "Class" : "Unknown",
+		 (recip == USB_RECIP_DEVICE)    ? "Device" :
+		 (recip == USB_RECIP_INTERFACE) ? "Interface" :
+		 (recip == USB_RECIP_ENDPOINT)  ? "Endpoint" : "Unknown",
+		 (bRequestType & USB_DIR_IN)    ? "IN" : "OUT",
+		 bRequest, wValue, wIndex, wLength);
+}
+
+static void usb_decode_ctrl_standard(char *str, size_t size, __u8 bRequestType,
+				     __u8 bRequest, __u16 wValue, __u16 wIndex,
+				     __u16 wLength)
+{
+	switch (bRequest) {
+	case USB_REQ_GET_STATUS:
+		usb_decode_get_status(bRequestType, wIndex, wLength, str, size);
+		break;
+	case USB_REQ_CLEAR_FEATURE:
+	case USB_REQ_SET_FEATURE:
+		usb_decode_set_clear_feature(bRequestType, bRequest, wValue,
+					     wIndex, str, size);
+		break;
+	case USB_REQ_SET_ADDRESS:
+		usb_decode_set_address(wValue, str, size);
+		break;
+	case USB_REQ_GET_DESCRIPTOR:
+	case USB_REQ_SET_DESCRIPTOR:
+		usb_decode_get_set_descriptor(bRequestType, bRequest, wValue,
+					      wIndex, wLength, str, size);
+		break;
+	case USB_REQ_GET_CONFIGURATION:
+		usb_decode_get_configuration(wLength, str, size);
+		break;
+	case USB_REQ_SET_CONFIGURATION:
+		usb_decode_set_configuration(wValue, str, size);
+		break;
+	case USB_REQ_GET_INTERFACE:
+		usb_decode_get_intf(wIndex, wLength, str, size);
+		break;
+	case USB_REQ_SET_INTERFACE:
+		usb_decode_set_intf(wValue, wIndex, str, size);
+		break;
+	case USB_REQ_SYNCH_FRAME:
+		usb_decode_synch_frame(wIndex, wLength, str, size);
+		break;
+	case USB_REQ_SET_SEL:
+		usb_decode_set_sel(wLength, str, size);
+		break;
+	case USB_REQ_SET_ISOCH_DELAY:
+		usb_decode_set_isoch_delay(wValue, str, size);
+		break;
+	default:
+		usb_decode_ctrl_generic(str, size, bRequestType, bRequest,
+					wValue, wIndex, wLength);
+		break;
+	}
+}
+
+/**
+ * usb_decode_ctrl - Returns human readable representation of control request.
+ * @str: buffer to return a human-readable representation of control request.
+ *       This buffer should have about 200 bytes.
+ * @size: size of str buffer.
+ * @bRequestType: matches the USB bmRequestType field
+ * @bRequest: matches the USB bRequest field
+ * @wValue: matches the USB wValue field (CPU byte order)
+ * @wIndex: matches the USB wIndex field (CPU byte order)
+ * @wLength: matches the USB wLength field (CPU byte order)
+ *
+ * Function returns decoded, formatted and human-readable description of
+ * control request packet.
+ *
+ * The usage scenario for this is for tracepoints, so function as a return
+ * use the same value as in parameters. This approach allows to use this
+ * function in TP_printk
+ *
+ * Important: wValue, wIndex, wLength parameters before invoking this function
+ * should be processed by le16_to_cpu macro.
+ */
+const char *usb_decode_ctrl(char *str, size_t size, __u8 bRequestType,
+			    __u8 bRequest, __u16 wValue, __u16 wIndex,
+			    __u16 wLength)
+{
+	switch (bRequestType & USB_TYPE_MASK) {
+	case USB_TYPE_STANDARD:
+		usb_decode_ctrl_standard(str, size, bRequestType, bRequest,
+					 wValue, wIndex, wLength);
+		break;
+	case USB_TYPE_VENDOR:
+	case USB_TYPE_CLASS:
+	default:
+		usb_decode_ctrl_generic(str, size, bRequestType, bRequest,
+					wValue, wIndex, wLength);
+		break;
+	}
+
+	return str;
+}
+EXPORT_SYMBOL_GPL(usb_decode_ctrl);