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>

2 files changed, 111 insertions, 0 deletions

diff --git a/Documentation/devicetree/bindings/csky/cpus.txt b/Documentation/devicetree/bindings/csky/cpus.txt
new file mode 100644
index 000000000..ae79412f2
--- /dev/null
+++ b/Documentation/devicetree/bindings/csky/cpus.txt
@@ -0,0 +1,73 @@
+==================
+C-SKY CPU Bindings
+==================
+
+The device tree allows to describe the layout of CPUs in a system through
+the "cpus" node, which in turn contains a number of subnodes (ie "cpu")
+defining properties for every cpu.
+
+Only SMP system need to care about the cpus node and single processor
+needn't define cpus node at all.
+
+=====================================
+cpus and cpu node bindings definition
+=====================================
+
+- cpus node
+
+	Description: Container of cpu nodes
+
+	The node name must be "cpus".
+
+	A cpus node must define the following properties:
+
+	- #address-cells
+		Usage: required
+		Value type: <u32>
+		Definition: must be set to 1
+	- #size-cells
+		Usage: required
+		Value type: <u32>
+		Definition: must be set to 0
+
+- cpu node
+
+	Description: Describes one of SMP cores
+
+	PROPERTIES
+
+	- device_type
+		Usage: required
+		Value type: <string>
+		Definition: must be "cpu"
+	- reg
+		Usage: required
+		Value type: <u32>
+		Definition: CPU index
+	- compatible:
+		Usage: required
+		Value type: <string>
+		Definition: must contain "csky", eg:
+			"csky,610"
+			"csky,807"
+			"csky,810"
+			"csky,860"
+
+Example:
+--------
+
+	cpus {
+		#address-cells = <1>;
+		#size-cells = <0>;
+		cpu@0 {
+			device_type = "cpu";
+			reg = <0>;
+			status = "ok";
+		};
+
+		cpu@1 {
+			device_type = "cpu";
+			reg = <1>;
+			status = "ok";
+		};
+	};
diff --git a/Documentation/devicetree/bindings/csky/pmu.txt b/Documentation/devicetree/bindings/csky/pmu.txt
new file mode 100644
index 000000000..728d05ca6
--- /dev/null
+++ b/Documentation/devicetree/bindings/csky/pmu.txt
@@ -0,0 +1,38 @@
+===============================
+C-SKY Performance Monitor Units
+===============================
+
+C-SKY Performance Monitor is designed for ck807/ck810/ck860 SMP soc and
+it could count cpu's events for helping analysis performance issues.
+
+============================
+PMU node bindings definition
+============================
+
+	Description: Describes PMU
+
+	PROPERTIES
+
+	- compatible
+		Usage: required
+		Value type: <string>
+		Definition: must be "csky,csky-pmu"
+	- interrupts
+		Usage: required
+		Value type: <u32 IRQ_TYPE_XXX>
+		Definition: must be pmu irq num defined by soc
+	- count-width
+		Usage: optional
+		Value type: <u32>
+		Definition: the width of pmu counter
+
+Examples:
+---------
+#include <dt-bindings/interrupt-controller/irq.h>
+
+	pmu: performace-monitor {
+		compatible = "csky,csky-pmu";
+		interrupts = <23 IRQ_TYPE_EDGE_RISING>;
+		interrupt-parent = <&intc>;
+		count-width = <48>;
+        };