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, 89 insertions, 0 deletions

diff --git a/Documentation/ABI/testing/sysfs-class-led b/Documentation/ABI/testing/sysfs-class-led
new file mode 100644
index 000000000..d4c918cc1
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-class-led
@@ -0,0 +1,89 @@
+What:		/sys/class/leds/<led>/brightness
+Date:		March 2006
+KernelVersion:	2.6.17
+Contact:	Richard Purdie <rpurdie@rpsys.net>
+Description:
+		Set the brightness of the LED.
+
+		Most LEDs don't have hardware brightness support, so will
+		just be turned on for non-zero brightness settings.
+
+		.. Note::
+
+		  For multicolor LEDs, writing to this file will update all
+		  LEDs within the group to a calculated percentage of what
+		  each color LED intensity is set to.
+
+		  The percentage is calculated for each grouped LED via
+		  the equation below::
+
+		    led_brightness = brightness * multi_intensity/max_brightness
+
+		  For additional details please refer to
+		  Documentation/leds/leds-class-multicolor.rst.
+
+		The value is between 0 and /sys/class/leds/<led>/max_brightness
+		and is represented by as a decimal.
+
+		Writing 0 to this file clears active trigger.
+
+		Writing non-zero to this file while trigger is active changes the
+		top brightness trigger is going to use.
+
+
+
+What:		/sys/class/leds/<led>/max_brightness
+Date:		March 2006
+KernelVersion:	2.6.17
+Contact:	Richard Purdie <rpurdie@rpsys.net>
+Description:
+		Maximum brightness level for this LED, default is 255 (LED_FULL).
+
+		If the LED does not support different brightness levels, this
+		should be 1.
+
+What:		/sys/class/leds/<led>/brightness_hw_changed
+Date:		January 2017
+KernelVersion:	4.11
+Description:
+		Last hardware set brightness level for this LED. Some LEDs
+		may be changed autonomously by hardware/firmware. Only LEDs
+		where this happens and the driver can detect this, will have
+		this file.
+
+		This file supports poll() to detect when the hardware changes
+		the brightness.
+
+		Reading this file will return the last brightness level set
+		by the hardware, this may be different from the current
+		brightness. Reading this file when no hw brightness change
+		event has happened will return an ENODATA error.
+
+What:		/sys/class/leds/<led>/trigger
+Date:		March 2006
+KernelVersion:	2.6.17
+Contact:	Richard Purdie <rpurdie@rpsys.net>
+Description:
+		Set the trigger for this LED. A trigger is a kernel based source
+		of LED events.
+
+		You can change triggers in a similar manner to the way an IO
+		scheduler is chosen. Trigger specific parameters can appear in
+		/sys/class/leds/<led> once a given trigger is selected. For
+		their documentation see `sysfs-class-led-trigger-*`.
+
+		Writing "none" removes the trigger for this LED.
+
+		Writing "default" sets the trigger to the LED's default trigger
+		(which would often be configured in the device tree for the
+		hardware).
+
+What:		/sys/class/leds/<led>/inverted
+Date:		January 2011
+KernelVersion:	2.6.38
+Contact:	Richard Purdie <rpurdie@rpsys.net>
+Description:
+		Invert the LED on/off state. This parameter is specific to
+		gpio and backlight triggers. In case of the backlight trigger,
+		it is useful when driving a LED which is intended to indicate
+		a device in a standby like state.