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, 152 insertions, 0 deletions

diff --git a/drivers/usb/misc/ezusb.c b/drivers/usb/misc/ezusb.c
new file mode 100644
index 000000000..7ab4856ab
--- /dev/null
+++ b/drivers/usb/misc/ezusb.c
@@ -0,0 +1,152 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * EZ-USB specific functions used by some of the USB to Serial drivers.
+ *
+ * Copyright (C) 1999 - 2002 Greg Kroah-Hartman (greg@kroah.com)
+ */
+
+#include <linux/kernel.h>
+#include <linux/slab.h>
+#include <linux/module.h>
+#include <linux/usb.h>
+#include <linux/firmware.h>
+#include <linux/ihex.h>
+#include <linux/usb/ezusb.h>
+
+struct ezusb_fx_type {
+	/* EZ-USB Control and Status Register.  Bit 0 controls 8051 reset */
+	unsigned short cpucs_reg;
+	unsigned short max_internal_adress;
+};
+
+static const struct ezusb_fx_type ezusb_fx1 = {
+	.cpucs_reg = 0x7F92,
+	.max_internal_adress = 0x1B3F,
+};
+
+/* Commands for writing to memory */
+#define WRITE_INT_RAM 0xA0
+#define WRITE_EXT_RAM 0xA3
+
+static int ezusb_writememory(struct usb_device *dev, int address,
+				unsigned char *data, int length, __u8 request)
+{
+	if (!dev)
+		return -ENODEV;
+
+	return usb_control_msg_send(dev, 0, request,
+				 USB_DIR_OUT | USB_TYPE_VENDOR | USB_RECIP_DEVICE,
+				 address, 0, data, length, 3000, GFP_KERNEL);
+}
+
+static int ezusb_set_reset(struct usb_device *dev, unsigned short cpucs_reg,
+			   unsigned char reset_bit)
+{
+	int response = ezusb_writememory(dev, cpucs_reg, &reset_bit, 1, WRITE_INT_RAM);
+	if (response < 0)
+		dev_err(&dev->dev, "%s-%d failed: %d\n",
+						__func__, reset_bit, response);
+	return response;
+}
+
+int ezusb_fx1_set_reset(struct usb_device *dev, unsigned char reset_bit)
+{
+	return ezusb_set_reset(dev, ezusb_fx1.cpucs_reg, reset_bit);
+}
+EXPORT_SYMBOL_GPL(ezusb_fx1_set_reset);
+
+static int ezusb_ihex_firmware_download(struct usb_device *dev,
+					struct ezusb_fx_type fx,
+					const char *firmware_path)
+{
+	int ret = -ENOENT;
+	const struct firmware *firmware = NULL;
+	const struct ihex_binrec *record;
+
+	if (request_ihex_firmware(&firmware, firmware_path,
+				  &dev->dev)) {
+		dev_err(&dev->dev,
+			"%s - request \"%s\" failed\n",
+			__func__, firmware_path);
+		goto out;
+	}
+
+	ret = ezusb_set_reset(dev, fx.cpucs_reg, 0);
+	if (ret < 0)
+		goto out;
+
+	record = (const struct ihex_binrec *)firmware->data;
+	for (; record; record = ihex_next_binrec(record)) {
+		if (be32_to_cpu(record->addr) > fx.max_internal_adress) {
+			ret = ezusb_writememory(dev, be32_to_cpu(record->addr),
+						(unsigned char *)record->data,
+						be16_to_cpu(record->len), WRITE_EXT_RAM);
+			if (ret < 0) {
+				dev_err(&dev->dev, "%s - ezusb_writememory "
+					"failed writing internal memory "
+					"(%d %04X %p %d)\n", __func__, ret,
+					be32_to_cpu(record->addr), record->data,
+					be16_to_cpu(record->len));
+				goto out;
+			}
+		}
+	}
+
+	ret = ezusb_set_reset(dev, fx.cpucs_reg, 1);
+	if (ret < 0)
+		goto out;
+	record = (const struct ihex_binrec *)firmware->data;
+	for (; record; record = ihex_next_binrec(record)) {
+		if (be32_to_cpu(record->addr) <= fx.max_internal_adress) {
+			ret = ezusb_writememory(dev, be32_to_cpu(record->addr),
+						(unsigned char *)record->data,
+						be16_to_cpu(record->len), WRITE_INT_RAM);
+			if (ret < 0) {
+				dev_err(&dev->dev, "%s - ezusb_writememory "
+					"failed writing external memory "
+					"(%d %04X %p %d)\n", __func__, ret,
+					be32_to_cpu(record->addr), record->data,
+					be16_to_cpu(record->len));
+				goto out;
+			}
+		}
+	}
+	ret = ezusb_set_reset(dev, fx.cpucs_reg, 0);
+out:
+	release_firmware(firmware);
+	return ret;
+}
+
+int ezusb_fx1_ihex_firmware_download(struct usb_device *dev,
+				     const char *firmware_path)
+{
+	return ezusb_ihex_firmware_download(dev, ezusb_fx1, firmware_path);
+}
+EXPORT_SYMBOL_GPL(ezusb_fx1_ihex_firmware_download);
+
+#if 0
+/*
+ * Once someone one needs these fx2 functions, uncomment them
+ * and add them to ezusb.h and all should be good.
+ */
+static struct ezusb_fx_type ezusb_fx2 = {
+	.cpucs_reg = 0xE600,
+	.max_internal_adress = 0x3FFF,
+};
+
+int ezusb_fx2_set_reset(struct usb_device *dev, unsigned char reset_bit)
+{
+	return ezusb_set_reset(dev, ezusb_fx2.cpucs_reg, reset_bit);
+}
+EXPORT_SYMBOL_GPL(ezusb_fx2_set_reset);
+
+int ezusb_fx2_ihex_firmware_download(struct usb_device *dev,
+				     const char *firmware_path)
+{
+	return ezusb_ihex_firmware_download(dev, ezusb_fx2, firmware_path);
+}
+EXPORT_SYMBOL_GPL(ezusb_fx2_ihex_firmware_download);
+#endif
+
+MODULE_DESCRIPTION("EZUSB device support");
+MODULE_LICENSE("GPL");