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, 143 insertions, 0 deletions

diff --git a/drivers/acpi/proc.c b/drivers/acpi/proc.c
new file mode 100644
index 000000000..c08ead072
--- /dev/null
+++ b/drivers/acpi/proc.c
@@ -0,0 +1,143 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/proc_fs.h>
+#include <linux/seq_file.h>
+#include <linux/string_choices.h>
+#include <linux/suspend.h>
+#include <linux/bcd.h>
+#include <linux/acpi.h>
+#include <linux/uaccess.h>
+
+#include "sleep.h"
+#include "internal.h"
+
+/*
+ * this file provides support for:
+ * /proc/acpi/wakeup
+ */
+
+static int
+acpi_system_wakeup_device_seq_show(struct seq_file *seq, void *offset)
+{
+	struct acpi_device *dev, *tmp;
+
+	seq_printf(seq, "Device\tS-state\t  Status   Sysfs node\n");
+
+	mutex_lock(&acpi_device_lock);
+	list_for_each_entry_safe(dev, tmp, &acpi_wakeup_device_list,
+				 wakeup_list) {
+		struct acpi_device_physical_node *entry;
+
+		if (!dev->wakeup.flags.valid)
+			continue;
+
+		seq_printf(seq, "%s\t  S%llu\t",
+			   dev->pnp.bus_id,
+			   dev->wakeup.sleep_state);
+
+		mutex_lock(&dev->physical_node_lock);
+
+		if (!dev->physical_node_count) {
+			seq_printf(seq, "%c%-8s\n",
+				dev->wakeup.flags.valid ? '*' : ' ',
+				str_enabled_disabled(device_may_wakeup(&dev->dev)));
+		} else {
+			struct device *ldev;
+			list_for_each_entry(entry, &dev->physical_node_list,
+					node) {
+				ldev = get_device(entry->dev);
+				if (!ldev)
+					continue;
+
+				if (&entry->node !=
+						dev->physical_node_list.next)
+					seq_printf(seq, "\t\t");
+
+				seq_printf(seq, "%c%-8s  %s:%s\n",
+					dev->wakeup.flags.valid ? '*' : ' ',
+					str_enabled_disabled(device_may_wakeup(ldev) ||
+							     device_may_wakeup(&dev->dev)),
+					ldev->bus ? ldev->bus->name :
+					"no-bus", dev_name(ldev));
+				put_device(ldev);
+			}
+		}
+
+		mutex_unlock(&dev->physical_node_lock);
+	}
+	mutex_unlock(&acpi_device_lock);
+	return 0;
+}
+
+static void physical_device_enable_wakeup(struct acpi_device *adev)
+{
+	struct acpi_device_physical_node *entry;
+
+	mutex_lock(&adev->physical_node_lock);
+
+	list_for_each_entry(entry,
+		&adev->physical_node_list, node)
+		if (entry->dev && device_can_wakeup(entry->dev)) {
+			bool enable = !device_may_wakeup(entry->dev);
+			device_set_wakeup_enable(entry->dev, enable);
+		}
+
+	mutex_unlock(&adev->physical_node_lock);
+}
+
+static ssize_t
+acpi_system_write_wakeup_device(struct file *file,
+				const char __user * buffer,
+				size_t count, loff_t * ppos)
+{
+	struct acpi_device *dev, *tmp;
+	char strbuf[5];
+	char str[5] = "";
+
+	if (count > 4)
+		count = 4;
+
+	if (copy_from_user(strbuf, buffer, count))
+		return -EFAULT;
+	strbuf[count] = '\0';
+	sscanf(strbuf, "%s", str);
+
+	mutex_lock(&acpi_device_lock);
+	list_for_each_entry_safe(dev, tmp, &acpi_wakeup_device_list,
+				 wakeup_list) {
+		if (!dev->wakeup.flags.valid)
+			continue;
+
+		if (!strncmp(dev->pnp.bus_id, str, 4)) {
+			if (device_can_wakeup(&dev->dev)) {
+				bool enable = !device_may_wakeup(&dev->dev);
+				device_set_wakeup_enable(&dev->dev, enable);
+			} else {
+				physical_device_enable_wakeup(dev);
+			}
+			break;
+		}
+	}
+	mutex_unlock(&acpi_device_lock);
+	return count;
+}
+
+static int
+acpi_system_wakeup_device_open_fs(struct inode *inode, struct file *file)
+{
+	return single_open(file, acpi_system_wakeup_device_seq_show,
+			   pde_data(inode));
+}
+
+static const struct proc_ops acpi_system_wakeup_device_proc_ops = {
+	.proc_open	= acpi_system_wakeup_device_open_fs,
+	.proc_read	= seq_read,
+	.proc_write	= acpi_system_write_wakeup_device,
+	.proc_lseek	= seq_lseek,
+	.proc_release	= single_release,
+};
+
+void __init acpi_sleep_proc_init(void)
+{
+	/* 'wakeup device' [R/W] */
+	proc_create("wakeup", 0644, acpi_root_dir, &acpi_system_wakeup_device_proc_ops);
+}