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, 61 insertions, 0 deletions

diff --git a/include/net/wext.h b/include/net/wext.h
new file mode 100644
index 000000000..aa192a670
--- /dev/null
+++ b/include/net/wext.h
@@ -0,0 +1,61 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __NET_WEXT_H
+#define __NET_WEXT_H
+
+#include <net/iw_handler.h>
+
+struct net;
+
+#ifdef CONFIG_WEXT_CORE
+int wext_handle_ioctl(struct net *net, unsigned int cmd,
+		      void __user *arg);
+int compat_wext_handle_ioctl(struct net *net, unsigned int cmd,
+			     unsigned long arg);
+
+struct iw_statistics *get_wireless_stats(struct net_device *dev);
+int call_commit_handler(struct net_device *dev);
+#else
+static inline int wext_handle_ioctl(struct net *net, unsigned int cmd,
+				    void __user *arg)
+{
+	return -EINVAL;
+}
+static inline int compat_wext_handle_ioctl(struct net *net, unsigned int cmd,
+					   unsigned long arg)
+{
+	return -EINVAL;
+}
+#endif
+
+#ifdef CONFIG_WEXT_PROC
+int wext_proc_init(struct net *net);
+void wext_proc_exit(struct net *net);
+#else
+static inline int wext_proc_init(struct net *net)
+{
+	return 0;
+}
+static inline void wext_proc_exit(struct net *net)
+{
+	return;
+}
+#endif
+
+#ifdef CONFIG_WEXT_PRIV
+int ioctl_private_call(struct net_device *dev, struct iwreq *iwr,
+		       unsigned int cmd, struct iw_request_info *info,
+		       iw_handler handler);
+int compat_private_call(struct net_device *dev, struct iwreq *iwr,
+			unsigned int cmd, struct iw_request_info *info,
+			iw_handler handler);
+int iw_handler_get_private(struct net_device *		dev,
+			   struct iw_request_info *	info,
+			   union iwreq_data *		wrqu,
+			   char *			extra);
+#else
+#define ioctl_private_call NULL
+#define compat_private_call NULL
+#endif
+
+
+#endif /* __NET_WEXT_H */