dmaengine: fix use-after-free in dma_chan_put() and dma_release_channel()grafted

When dma_device_put() drops the last reference on chan->device->ref,
dma_device_release() runs and may free the dma_device along with its
channels.

dma_chan_put() then still reads chan->device->owner via
dma_chan_to_owner() for the trailing module_put(). KASAN catches it:

	slab-use-after-free in dma_chan_put+0x3e6/0x4c0
	Read of size 8 by task insmod/6319
	Freed by task 6319:
	  kfree+0x225/0x470
	  dma_chan_put+0x395/0x4c0
	  dmaengine_put+0xf8/0x160

Cache the module owner in dma_chan_put() before the put so the trailing
module_put() does not need chan->device.

Fixes: 8ad342a86359 ("dmaengine: Add reference counting to dma_device struct")
Suggested-by: Sashiko <sashiko-bot@kernel.org>
Link: https://sashiko.dev/#/patchset/20260518-dmaengine-kref-fix-v1-1-4d6125048fb7@amd.com
Reviewed-by: Frank Li <Frank.Li@nxp.com>
Reviewed-by: Logan Gunthorpe <logang@deltatee.com>
Signed-off-by: Shivank Garg <shivankg@amd.com>
Link: https://patch.msgid.link/20260822-dmaengine-kref-fix-v5-3-d4a4ee47d927@amd.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>

1 files changed, 49 insertions, 0 deletions

diff --git a/Documentation/devicetree/bindings/pps/pps-gpio.yaml b/Documentation/devicetree/bindings/pps/pps-gpio.yaml
new file mode 100644
index 000000000..383a83874
--- /dev/null
+++ b/Documentation/devicetree/bindings/pps/pps-gpio.yaml
@@ -0,0 +1,49 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/pps/pps-gpio.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: PPS Signal via GPIO
+
+maintainers:
+  - Fabio Estevam <festevam@gmail.com>
+
+properties:
+  compatible:
+    const: pps-gpio
+
+  gpios:
+    description: The GPIO that provides the PPS signal.
+    maxItems: 1
+
+  echo-gpios:
+    description: The GPIO that provides the PPS ECHO signal.
+    maxItems: 1
+
+  echo-active-ms:
+    description: Duration in ms of the active portion of the echo pulse.
+
+  assert-falling-edge:
+    description: Indicates a falling edge assert, when present. Rising edge if absent.
+    type: boolean
+
+required:
+  - compatible
+  - gpios
+
+additionalProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/gpio/gpio.h>
+
+    pps {
+        compatible = "pps-gpio";
+        pinctrl-names = "default";
+        pinctrl-0 = <&pinctrl_pps>;
+        gpios = <&gpio1 26 GPIO_ACTIVE_HIGH>;
+        assert-falling-edge;
+        echo-gpios = <&gpio1 27 GPIO_ACTIVE_HIGH>;
+        echo-active-ms = <100>;
+    };