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, 272 insertions, 0 deletions

diff --git a/Documentation/devicetree/bindings/dpll/dpll-device.yaml b/Documentation/devicetree/bindings/dpll/dpll-device.yaml
new file mode 100644
index 000000000..fb8d7a9a3
--- /dev/null
+++ b/Documentation/devicetree/bindings/dpll/dpll-device.yaml
@@ -0,0 +1,76 @@
+# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/dpll/dpll-device.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Digital Phase-Locked Loop (DPLL) Device
+
+maintainers:
+  - Ivan Vecera <ivecera@redhat.com>
+
+description:
+  Digital Phase-Locked Loop (DPLL) device is used for precise clock
+  synchronization in networking and telecom hardware. The device can
+  have one or more channels (DPLLs) and one or more physical input and
+  output pins. Each DPLL channel can either produce pulse-per-clock signal
+  or drive ethernet equipment clock. The type of each channel can be
+  indicated by dpll-types property.
+
+properties:
+  $nodename:
+    pattern: "^dpll(@.*)?$"
+
+  "#address-cells":
+    const: 0
+
+  "#size-cells":
+    const: 0
+
+  dpll-types:
+    description: List of DPLL channel types, one per DPLL instance.
+    $ref: /schemas/types.yaml#/definitions/non-unique-string-array
+    items:
+      enum: [pps, eec]
+
+  input-pins:
+    type: object
+    description: DPLL input pins
+    unevaluatedProperties: false
+
+    properties:
+      "#address-cells":
+        const: 1
+      "#size-cells":
+        const: 0
+
+    patternProperties:
+      "^pin@[0-9a-f]+$":
+        $ref: /schemas/dpll/dpll-pin.yaml
+        unevaluatedProperties: false
+
+    required:
+      - "#address-cells"
+      - "#size-cells"
+
+  output-pins:
+    type: object
+    description: DPLL output pins
+    unevaluatedProperties: false
+
+    properties:
+      "#address-cells":
+        const: 1
+      "#size-cells":
+        const: 0
+
+    patternProperties:
+      "^pin@[0-9]+$":
+        $ref: /schemas/dpll/dpll-pin.yaml
+        unevaluatedProperties: false
+
+    required:
+      - "#address-cells"
+      - "#size-cells"
+
+additionalProperties: true
diff --git a/Documentation/devicetree/bindings/dpll/dpll-pin.yaml b/Documentation/devicetree/bindings/dpll/dpll-pin.yaml
new file mode 100644
index 000000000..1287a472f
--- /dev/null
+++ b/Documentation/devicetree/bindings/dpll/dpll-pin.yaml
@@ -0,0 +1,58 @@
+# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/dpll/dpll-pin.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: DPLL Pin
+
+maintainers:
+  - Ivan Vecera <ivecera@redhat.com>
+
+description: |
+  The DPLL pin is either a physical input or output pin that is provided
+  by a DPLL( Digital Phase-Locked Loop) device. The pin is identified by
+  its physical order number that is stored in reg property and can have
+  an additional set of properties like supported (allowed) frequencies,
+  label, type and may support embedded sync.
+
+  Note that the pin in this context has nothing to do with pinctrl.
+
+properties:
+  reg:
+    description: Hardware index of the DPLL pin.
+    maxItems: 1
+
+  connection-type:
+    description: Connection type of the pin
+    $ref: /schemas/types.yaml#/definitions/string
+    enum: [ext, gnss, int, mux, synce]
+
+  esync-control:
+    description: Indicates whether the pin supports embedded sync functionality.
+    type: boolean
+
+  label:
+    description: String exposed as the pin board label
+    $ref: /schemas/types.yaml#/definitions/string
+
+  ref-sync-sources:
+    description: |
+      List of phandles to input pins that can serve as the sync source
+      in a Reference-Sync pair with this pin acting as the clock source.
+      A Ref-Sync pair consists of a clock reference and a low-frequency
+      sync signal.  The DPLL locks to the clock reference but
+      phase-aligns to the sync reference.
+      Only valid for input pins.  Each referenced pin must be a
+      different input pin on the same device.
+    $ref: /schemas/types.yaml#/definitions/phandle-array
+    items:
+      maxItems: 1
+
+  supported-frequencies-hz:
+    description: List of supported frequencies for this pin, expressed in Hz.
+
+required:
+  - reg
+
+additionalProperties: false
diff --git a/Documentation/devicetree/bindings/dpll/microchip,zl30731.yaml b/Documentation/devicetree/bindings/dpll/microchip,zl30731.yaml
new file mode 100644
index 000000000..17983e6c3
--- /dev/null
+++ b/Documentation/devicetree/bindings/dpll/microchip,zl30731.yaml
@@ -0,0 +1,138 @@
+# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/dpll/microchip,zl30731.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Microchip Azurite DPLL device
+
+maintainers:
+  - Ivan Vecera <ivecera@redhat.com>
+
+description:
+  Microchip Azurite DPLL (ZL3073x) is a family of DPLL devices that
+  provides up to 5 independent DPLL channels, up to 10 differential or
+  single-ended inputs and 10 differential or 20 single-ended outputs.
+  These devices support both I2C and SPI interfaces.
+  The ZL3064x line card timing ICs  share the ZL3073x register map
+  and are described with a fallback to the register equivalent ZL3073x
+  part.
+
+properties:
+  compatible:
+    oneOf:
+      - enum:
+          - microchip,zl30731
+          - microchip,zl30732
+          - microchip,zl30733
+          - microchip,zl30734
+          - microchip,zl30735
+      - items:
+          - const: microchip,zl30643
+          - const: microchip,zl30733
+
+  reg:
+    maxItems: 1
+
+required:
+  - compatible
+  - reg
+
+allOf:
+  - $ref: /schemas/dpll/dpll-device.yaml#
+  - $ref: /schemas/spi/spi-peripheral-props.yaml#
+
+unevaluatedProperties: false
+
+examples:
+  - |
+    i2c {
+      #address-cells = <1>;
+      #size-cells = <0>;
+
+      dpll@70 {
+        compatible = "microchip,zl30732";
+        reg = <0x70>;
+        dpll-types = "pps", "eec";
+
+        input-pins {
+          #address-cells = <1>;
+          #size-cells = <0>;
+
+          sync0: pin@0 { /* REF0P - 1 PPS sync source */
+            reg = <0>;
+            connection-type = "ext";
+            label = "SMA1";
+            supported-frequencies-hz = /bits/ 64 <1>;
+          };
+
+          pin@1 { /* REF0N - clock source, can pair with sync0 */
+            reg = <1>;
+            connection-type = "ext";
+            label = "SMA2";
+            supported-frequencies-hz = /bits/ 64 <10000 10000000>;
+            ref-sync-sources = <&sync0>;
+          };
+        };
+
+        output-pins {
+          #address-cells = <1>;
+          #size-cells = <0>;
+
+          pin@3 { /* OUT1N */
+            reg = <3>;
+            connection-type = "gnss";
+            esync-control;
+            label = "Output 1";
+            supported-frequencies-hz = /bits/ 64 <1 10000>;
+          };
+        };
+      };
+    };
+  - |
+    spi {
+      #address-cells = <1>;
+      #size-cells = <0>;
+
+      dpll@70 {
+        compatible = "microchip,zl30731";
+        reg = <0x70>;
+        spi-max-frequency = <12500000>;
+
+        dpll-types = "pps";
+
+        input-pins {
+          #address-cells = <1>;
+          #size-cells = <0>;
+
+          sync1: pin@0 { /* REF0P - 1 PPS sync source */
+            reg = <0>;
+            connection-type = "gnss";
+            label = "GNSS_1PPS_IN";
+            supported-frequencies-hz = /bits/ 64 <1>;
+          };
+
+          pin@1 { /* REF0N - clock source */
+            reg = <1>;
+            connection-type = "gnss";
+            label = "GNSS_10M_IN";
+            supported-frequencies-hz = /bits/ 64 <10000000>;
+            ref-sync-sources = <&sync1>;
+          };
+        };
+
+        output-pins {
+          #address-cells = <1>;
+          #size-cells = <0>;
+
+          pin@3 { /* OUT1N */
+            reg = <3>;
+            connection-type = "gnss";
+            esync-control;
+            label = "Output 1";
+            supported-frequencies-hz = /bits/ 64 <1 10000>;
+          };
+        };
+      };
+    };
+...