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>

3 files changed, 205 insertions, 0 deletions

diff --git a/Documentation/devicetree/bindings/hsi/client-devices.txt b/Documentation/devicetree/bindings/hsi/client-devices.txt
new file mode 100644
index 000000000..104c9a3e5
--- /dev/null
+++ b/Documentation/devicetree/bindings/hsi/client-devices.txt
@@ -0,0 +1,44 @@
+Each HSI port is supposed to have one child node, which
+symbols the remote device connected to the HSI port. The
+following properties are standardized for HSI clients:
+
+Required HSI configuration properties:
+
+- hsi-channel-ids:	A list of channel ids
+
+- hsi-rx-mode:		Receiver Bit transmission mode ("stream" or "frame")
+- hsi-tx-mode:		Transmitter Bit transmission mode ("stream" or "frame")
+- hsi-mode:		May be used instead hsi-rx-mode and hsi-tx-mode if
+			the transmission mode is the same for receiver and
+			transmitter
+- hsi-speed-kbps:	Max bit transmission speed in kbit/s
+- hsi-flow:		RX flow type ("synchronized" or "pipeline")
+- hsi-arb-mode:		Arbitration mode for TX frame ("round-robin", "priority")
+
+Optional HSI configuration properties:
+
+- hsi-channel-names:	A list with one name per channel specified in the
+			hsi-channel-ids property
+
+
+Device Tree node example for an HSI client:
+
+hsi-controller {
+	hsi-port {
+		modem: hsi-client {
+			compatible = "nokia,n900-modem";
+
+			hsi-channel-ids = <0>, <1>, <2>, <3>;
+			hsi-channel-names = "mcsaab-control",
+					    "speech-control",
+					    "speech-data",
+					    "mcsaab-data";
+			hsi-speed-kbps = <55000>;
+			hsi-mode = "frame";
+			hsi-flow = "synchronized";
+			hsi-arb-mode = "round-robin";
+
+			/* more client specific properties */
+		};
+	};
+};
diff --git a/Documentation/devicetree/bindings/hsi/nokia-modem.txt b/Documentation/devicetree/bindings/hsi/nokia-modem.txt
new file mode 100644
index 000000000..53de1d9d0
--- /dev/null
+++ b/Documentation/devicetree/bindings/hsi/nokia-modem.txt
@@ -0,0 +1,59 @@
+Nokia modem client bindings
+
+The Nokia modem HSI client follows the common HSI client binding
+and inherits all required properties. The following additional
+properties are needed by the Nokia modem HSI client:
+
+Required properties:
+- compatible:		Should be one of
+      "nokia,n900-modem"
+      "nokia,n950-modem"
+      "nokia,n9-modem"
+- hsi-channel-names:	Should contain the following strings
+      "mcsaab-control"
+      "speech-control"
+      "speech-data"
+      "mcsaab-data"
+- gpios:		Should provide a GPIO handler for each GPIO listed in
+                        gpio-names
+- gpio-names:		Should contain the following strings
+      "cmt_apeslpx" (for n900, n950, n9)
+      "cmt_rst_rq"  (for n900, n950, n9)
+      "cmt_en"      (for n900, n950, n9)
+      "cmt_rst"     (for n900)
+      "cmt_bsi"     (for n900)
+- interrupts:		Should be IRQ handle for modem's reset indication
+
+Example:
+
+&ssi_port {
+	modem: hsi-client {
+		compatible = "nokia,n900-modem";
+
+		pinctrl-names = "default";
+		pinctrl-0 = <&modem_pins>;
+
+		hsi-channel-ids = <0>, <1>, <2>, <3>;
+		hsi-channel-names = "mcsaab-control",
+				    "speech-control",
+				    "speech-data",
+				    "mcsaab-data";
+		hsi-speed-kbps = <55000>;
+		hsi-mode = "frame";
+		hsi-flow = "synchronized";
+		hsi-arb-mode = "round-robin";
+
+		interrupts-extended = <&gpio3 8 IRQ_TYPE_EDGE_FALLING>; /* 72 */
+
+		gpios = <&gpio3  6 GPIO_ACTIVE_HIGH>, /* 70 */
+			<&gpio3  9 GPIO_ACTIVE_HIGH>, /* 73 */
+			<&gpio3 10 GPIO_ACTIVE_HIGH>, /* 74 */
+			<&gpio3 11 GPIO_ACTIVE_HIGH>, /* 75 */
+			<&gpio5 29 GPIO_ACTIVE_HIGH>; /* 157 */
+		gpio-names = "cmt_apeslpx",
+			     "cmt_rst_rq",
+			     "cmt_en",
+			     "cmt_rst",
+			     "cmt_bsi";
+	};
+};
diff --git a/Documentation/devicetree/bindings/hsi/omap-ssi.txt b/Documentation/devicetree/bindings/hsi/omap-ssi.txt
new file mode 100644
index 000000000..77a0c3c30
--- /dev/null
+++ b/Documentation/devicetree/bindings/hsi/omap-ssi.txt
@@ -0,0 +1,102 @@
+OMAP SSI controller bindings
+
+OMAP3's Synchronous Serial Interface (SSI) controller implements a
+legacy variant of MIPI's High Speed Synchronous Serial Interface (HSI),
+while the controller found inside OMAP4 is supposed to be fully compliant
+with the HSI standard.
+
+Required properties:
+- compatible:		Should include "ti,omap3-ssi" or "ti,omap4-hsi"
+- reg-names:		Contains the values "sys" and "gdd" (in this order).
+- reg:			Contains a matching register specifier for each entry
+			in reg-names.
+- interrupt-names:	Contains the value "gdd_mpu".
+- interrupts: 		Contains matching interrupt information for each entry
+			in interrupt-names.
+- ranges:		Represents the bus address mapping between the main
+			controller node and the child nodes below.
+- clock-names:		Must include the following entries:
+  "ssi_ssr_fck": The OMAP clock of that name
+  "ssi_sst_fck": The OMAP clock of that name
+  "ssi_ick": The OMAP clock of that name
+- clocks:		Contains a matching clock specifier for each entry in
+			clock-names.
+- #address-cells:	Should be set to <1>
+- #size-cells:		Should be set to <1>
+
+Each port is represented as a sub-node of the ti,omap3-ssi device.
+
+Required Port sub-node properties:
+- compatible:		Should be set to the following value
+			ti,omap3-ssi-port (applicable to OMAP34xx devices)
+			ti,omap4-hsi-port (applicable to OMAP44xx devices)
+- reg-names:		Contains the values "tx" and "rx" (in this order).
+- reg:			Contains a matching register specifier for each entry
+			in reg-names.
+- interrupts:		Should contain interrupt specifiers for mpu interrupts
+			0 and 1 (in this order).
+- ti,ssi-cawake-gpio:	Defines which GPIO pin is used to signify CAWAKE
+			events for the port. This is an optional board-specific
+			property. If it's missing the port will not be
+			enabled.
+
+Optional properties:
+- ti,hwmods:		Shall contain TI interconnect module name if needed
+			by the SoC
+
+Example for Nokia N900:
+
+ssi-controller@48058000 {
+	compatible = "ti,omap3-ssi";
+
+	/* needed until hwmod is updated to use the compatible string */
+	ti,hwmods = "ssi";
+
+	reg = <0x48058000 0x1000>,
+	      <0x48059000 0x1000>;
+	reg-names = "sys",
+		    "gdd";
+
+	interrupts = <55>;
+	interrupt-names = "gdd_mpu";
+
+	clocks = <&ssi_ssr_fck>,
+		 <&ssi_sst_fck>,
+		 <&ssi_ick>;
+	clock-names = "ssi_ssr_fck",
+		      "ssi_sst_fck",
+		      "ssi_ick";
+
+	#address-cells = <1>;
+	#size-cells = <1>;
+	ranges;
+
+	ssi-port@4805a000 {
+		compatible = "ti,omap3-ssi-port";
+
+		reg = <0x4805a000 0x800>,
+		      <0x4805a800 0x800>;
+		reg-names = "tx",
+			    "rx";
+
+		interrupt-parent = <&intc>;
+		interrupts = <67>,
+			     <68>;
+
+		ti,ssi-cawake-gpio = <&gpio5 23 GPIO_ACTIVE_HIGH>; /* 151 */
+	}
+
+	ssi-port@4805a000 {
+		compatible = "ti,omap3-ssi-port";
+
+		reg = <0x4805b000 0x800>,
+		      <0x4805b800 0x800>;
+		reg-names = "tx",
+			    "rx";
+
+		interrupt-parent = <&intc>;
+		interrupts = <69>,
+			     <70>;
+
+	}
+}