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, 313 insertions, 0 deletions

diff --git a/drivers/usb/chipidea/debug.c b/drivers/usb/chipidea/debug.c
new file mode 100644
index 000000000..e72c43615
--- /dev/null
+++ b/drivers/usb/chipidea/debug.c
@@ -0,0 +1,313 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/kernel.h>
+#include <linux/device.h>
+#include <linux/types.h>
+#include <linux/spinlock.h>
+#include <linux/debugfs.h>
+#include <linux/seq_file.h>
+#include <linux/uaccess.h>
+#include <linux/usb/ch9.h>
+#include <linux/usb/gadget.h>
+#include <linux/usb/phy.h>
+#include <linux/usb/otg.h>
+#include <linux/usb/otg-fsm.h>
+#include <linux/usb/chipidea.h>
+
+#include "ci.h"
+#include "udc.h"
+#include "bits.h"
+#include "otg.h"
+
+/*
+ * ci_device_show: prints information about device capabilities and status
+ */
+static int ci_device_show(struct seq_file *s, void *data)
+{
+	struct ci_hdrc *ci = s->private;
+	struct usb_gadget *gadget = &ci->gadget;
+
+	seq_printf(s, "speed             = %d\n", gadget->speed);
+	seq_printf(s, "max_speed         = %d\n", gadget->max_speed);
+	seq_printf(s, "is_otg            = %d\n", gadget->is_otg);
+	seq_printf(s, "is_a_peripheral   = %d\n", gadget->is_a_peripheral);
+	seq_printf(s, "b_hnp_enable      = %d\n", gadget->b_hnp_enable);
+	seq_printf(s, "a_hnp_support     = %d\n", gadget->a_hnp_support);
+	seq_printf(s, "a_alt_hnp_support = %d\n", gadget->a_alt_hnp_support);
+	seq_printf(s, "name              = %s\n",
+		   (gadget->name ? gadget->name : ""));
+
+	if (!ci->driver)
+		return 0;
+
+	seq_printf(s, "gadget function   = %s\n",
+		       (ci->driver->function ? ci->driver->function : ""));
+	seq_printf(s, "gadget max speed  = %d\n", ci->driver->max_speed);
+
+	return 0;
+}
+DEFINE_SHOW_ATTRIBUTE(ci_device);
+
+/*
+ * ci_port_test_show: reads port test mode
+ */
+static int ci_port_test_show(struct seq_file *s, void *data)
+{
+	struct ci_hdrc *ci = s->private;
+	unsigned long flags;
+	unsigned mode;
+
+	pm_runtime_get_sync(ci->dev);
+	spin_lock_irqsave(&ci->lock, flags);
+	mode = hw_port_test_get(ci);
+	spin_unlock_irqrestore(&ci->lock, flags);
+	pm_runtime_put_sync(ci->dev);
+
+	seq_printf(s, "mode = %u\n", mode);
+
+	return 0;
+}
+
+/*
+ * ci_port_test_write: writes port test mode
+ */
+static ssize_t ci_port_test_write(struct file *file, const char __user *ubuf,
+				  size_t count, loff_t *ppos)
+{
+	struct seq_file *s = file->private_data;
+	struct ci_hdrc *ci = s->private;
+	unsigned long flags;
+	unsigned mode;
+	char buf[32];
+	int ret;
+
+	count = min_t(size_t, sizeof(buf) - 1, count);
+	if (copy_from_user(buf, ubuf, count))
+		return -EFAULT;
+
+	/* sscanf requires a zero terminated string */
+	buf[count] = '\0';
+
+	if (sscanf(buf, "%u", &mode) != 1)
+		return -EINVAL;
+
+	if (mode > 255)
+		return -EBADRQC;
+
+	pm_runtime_get_sync(ci->dev);
+	spin_lock_irqsave(&ci->lock, flags);
+	ret = hw_port_test_set(ci, mode);
+	spin_unlock_irqrestore(&ci->lock, flags);
+	pm_runtime_put_sync(ci->dev);
+
+	return ret ? ret : count;
+}
+
+static int ci_port_test_open(struct inode *inode, struct file *file)
+{
+	return single_open(file, ci_port_test_show, inode->i_private);
+}
+
+static const struct file_operations ci_port_test_fops = {
+	.open		= ci_port_test_open,
+	.write		= ci_port_test_write,
+	.read		= seq_read,
+	.llseek		= seq_lseek,
+	.release	= single_release,
+};
+
+/*
+ * ci_qheads_show: DMA contents of all queue heads
+ */
+static int ci_qheads_show(struct seq_file *s, void *data)
+{
+	struct ci_hdrc *ci = s->private;
+	unsigned long flags;
+	unsigned i, j;
+
+	if (ci->role != CI_ROLE_GADGET) {
+		seq_printf(s, "not in gadget mode\n");
+		return 0;
+	}
+
+	spin_lock_irqsave(&ci->lock, flags);
+	for (i = 0; i < ci->hw_ep_max/2; i++) {
+		struct ci_hw_ep *hweprx = &ci->ci_hw_ep[i];
+		struct ci_hw_ep *hweptx =
+			&ci->ci_hw_ep[i + ci->hw_ep_max/2];
+		seq_printf(s, "EP=%02i: RX=%08X TX=%08X\n",
+			   i, (u32)hweprx->qh.dma, (u32)hweptx->qh.dma);
+		for (j = 0; j < (sizeof(struct ci_hw_qh)/sizeof(u32)); j++)
+			seq_printf(s, " %04X:    %08X    %08X\n", j,
+				   *((u32 *)hweprx->qh.ptr + j),
+				   *((u32 *)hweptx->qh.ptr + j));
+	}
+	spin_unlock_irqrestore(&ci->lock, flags);
+
+	return 0;
+}
+DEFINE_SHOW_ATTRIBUTE(ci_qheads);
+
+/*
+ * ci_requests_show: DMA contents of all requests currently queued (all endpts)
+ */
+static int ci_requests_show(struct seq_file *s, void *data)
+{
+	struct ci_hdrc *ci = s->private;
+	unsigned long flags;
+	struct ci_hw_req *req = NULL;
+	struct td_node *node, *tmpnode;
+	unsigned i, j, qsize = sizeof(struct ci_hw_td)/sizeof(u32);
+
+	if (ci->role != CI_ROLE_GADGET) {
+		seq_printf(s, "not in gadget mode\n");
+		return 0;
+	}
+
+	spin_lock_irqsave(&ci->lock, flags);
+	for (i = 0; i < ci->hw_ep_max; i++)
+		list_for_each_entry(req, &ci->ci_hw_ep[i].qh.queue, queue) {
+			list_for_each_entry_safe(node, tmpnode, &req->tds, td) {
+				seq_printf(s, "EP=%02i: TD=%08X %s\n",
+					   i % (ci->hw_ep_max / 2),
+					   (u32)node->dma,
+					   ((i < ci->hw_ep_max/2) ?
+					   "RX" : "TX"));
+
+				for (j = 0; j < qsize; j++)
+					seq_printf(s, " %04X:    %08X\n", j,
+						   *((u32 *)node->ptr + j));
+			}
+		}
+	spin_unlock_irqrestore(&ci->lock, flags);
+
+	return 0;
+}
+DEFINE_SHOW_ATTRIBUTE(ci_requests);
+
+static int ci_otg_show(struct seq_file *s, void *unused)
+{
+	struct ci_hdrc *ci = s->private;
+	struct otg_fsm *fsm;
+
+	if (!ci || !ci_otg_is_fsm_mode(ci))
+		return 0;
+
+	fsm = &ci->fsm;
+
+	/* ------ State ----- */
+	seq_printf(s, "OTG state: %s\n\n",
+			usb_otg_state_string(ci->otg.state));
+
+	/* ------ State Machine Variables ----- */
+	seq_printf(s, "a_bus_drop: %d\n", fsm->a_bus_drop);
+
+	seq_printf(s, "a_bus_req: %d\n", fsm->a_bus_req);
+
+	seq_printf(s, "a_srp_det: %d\n", fsm->a_srp_det);
+
+	seq_printf(s, "a_vbus_vld: %d\n", fsm->a_vbus_vld);
+
+	seq_printf(s, "b_conn: %d\n", fsm->b_conn);
+
+	seq_printf(s, "adp_change: %d\n", fsm->adp_change);
+
+	seq_printf(s, "power_up: %d\n", fsm->power_up);
+
+	seq_printf(s, "a_bus_resume: %d\n", fsm->a_bus_resume);
+
+	seq_printf(s, "a_bus_suspend: %d\n", fsm->a_bus_suspend);
+
+	seq_printf(s, "a_conn: %d\n", fsm->a_conn);
+
+	seq_printf(s, "b_bus_req: %d\n", fsm->b_bus_req);
+
+	seq_printf(s, "b_bus_suspend: %d\n", fsm->b_bus_suspend);
+
+	seq_printf(s, "b_se0_srp: %d\n", fsm->b_se0_srp);
+
+	seq_printf(s, "b_ssend_srp: %d\n", fsm->b_ssend_srp);
+
+	seq_printf(s, "b_sess_vld: %d\n", fsm->b_sess_vld);
+
+	seq_printf(s, "b_srp_done: %d\n", fsm->b_srp_done);
+
+	seq_printf(s, "drv_vbus: %d\n", fsm->drv_vbus);
+
+	seq_printf(s, "loc_conn: %d\n", fsm->loc_conn);
+
+	seq_printf(s, "loc_sof: %d\n", fsm->loc_sof);
+
+	seq_printf(s, "adp_prb: %d\n", fsm->adp_prb);
+
+	seq_printf(s, "id: %d\n", fsm->id);
+
+	seq_printf(s, "protocol: %d\n", fsm->protocol);
+
+	return 0;
+}
+DEFINE_SHOW_ATTRIBUTE(ci_otg);
+
+static int ci_registers_show(struct seq_file *s, void *unused)
+{
+	struct ci_hdrc *ci = s->private;
+	u32 tmp_reg;
+
+	if (!ci || ci->in_lpm)
+		return -EPERM;
+
+	/* ------ Registers ----- */
+	tmp_reg = hw_read_intr_enable(ci);
+	seq_printf(s, "USBINTR reg: %08x\n", tmp_reg);
+
+	tmp_reg = hw_read_intr_status(ci);
+	seq_printf(s, "USBSTS reg: %08x\n", tmp_reg);
+
+	tmp_reg = hw_read(ci, OP_USBMODE, ~0);
+	seq_printf(s, "USBMODE reg: %08x\n", tmp_reg);
+
+	tmp_reg = hw_read(ci, OP_USBCMD, ~0);
+	seq_printf(s, "USBCMD reg: %08x\n", tmp_reg);
+
+	tmp_reg = hw_read(ci, OP_PORTSC, ~0);
+	seq_printf(s, "PORTSC reg: %08x\n", tmp_reg);
+
+	if (ci->is_otg) {
+		tmp_reg = hw_read_otgsc(ci, ~0);
+		seq_printf(s, "OTGSC reg: %08x\n", tmp_reg);
+	}
+
+	return 0;
+}
+DEFINE_SHOW_ATTRIBUTE(ci_registers);
+
+/**
+ * dbg_create_files: initializes the attribute interface
+ * @ci: device
+ *
+ * This function returns an error code
+ */
+void dbg_create_files(struct ci_hdrc *ci)
+{
+	struct dentry *dir;
+
+	dir = debugfs_create_dir(dev_name(ci->dev), usb_debug_root);
+
+	debugfs_create_file("device", S_IRUGO, dir, ci, &ci_device_fops);
+	debugfs_create_file("port_test", S_IRUGO | S_IWUSR, dir, ci, &ci_port_test_fops);
+	debugfs_create_file("qheads", S_IRUGO, dir, ci, &ci_qheads_fops);
+	debugfs_create_file("requests", S_IRUGO, dir, ci, &ci_requests_fops);
+
+	if (ci_otg_is_fsm_mode(ci))
+		debugfs_create_file("otg", S_IRUGO, dir, ci, &ci_otg_fops);
+
+	debugfs_create_file("registers", S_IRUGO, dir, ci, &ci_registers_fops);
+}
+
+/**
+ * dbg_remove_files: destroys the attribute interface
+ * @ci: device
+ */
+void dbg_remove_files(struct ci_hdrc *ci)
+{
+	debugfs_lookup_and_remove(dev_name(ci->dev), usb_debug_root);
+}