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, 28 insertions, 0 deletions

diff --git a/include/net/ipconfig.h b/include/net/ipconfig.h
new file mode 100644
index 000000000..8276897d0
--- /dev/null
+++ b/include/net/ipconfig.h
@@ -0,0 +1,28 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ *  Copyright (C) 1997 Martin Mares
+ *
+ *  Automatic IP Layer Configuration
+ */
+
+/* The following are initdata: */
+
+#include <linux/types.h>
+
+extern int ic_proto_enabled;	/* Protocols enabled (see IC_xxx) */
+extern int ic_set_manually;	/* IPconfig parameters set manually */
+
+extern __be32 ic_myaddr;		/* My IP address */
+extern __be32 ic_gateway;		/* Gateway IP address */
+
+extern __be32 ic_servaddr;		/* Boot server IP address */
+
+extern __be32 root_server_addr;	/* Address of NFS server */
+extern u8 root_server_path[];	/* Path to mount as root */
+
+
+/* bits in ic_proto_{enabled,used} */
+#define IC_PROTO	0xFF	/* Protocols mask: */
+#define IC_BOOTP	0x01	/*   BOOTP (or DHCP, see below) */
+#define IC_RARP		0x02	/*   RARP */
+#define IC_USE_DHCP    0x100	/* If on, use DHCP instead of BOOTP */