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-flash b/Documentation/ABI/testing/sysfs-class-led-flash
new file mode 100644
index 000000000..11e5677c3
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-class-led-flash
@@ -0,0 +1,89 @@
+What:		/sys/class/leds/<led>/flash_brightness
+Date:		March 2015
+KernelVersion:	4.0
+Contact:	Jacek Anaszewski <j.anaszewski@samsung.com>
+Description:	read/write
+		Set the brightness of this LED in the flash strobe mode, in
+		microamperes. The file is created only for the flash LED devices
+		that support setting flash brightness.
+
+		The value is between 0 and
+		/sys/class/leds/<led>/max_flash_brightness.
+
+What:		/sys/class/leds/<led>/max_flash_brightness
+Date:		March 2015
+KernelVersion:	4.0
+Contact:	Jacek Anaszewski <j.anaszewski@samsung.com>
+Description:	read only
+		Maximum brightness level for this LED in the flash strobe mode,
+		in microamperes.
+
+What:		/sys/class/leds/<led>/flash_timeout
+Date:		March 2015
+KernelVersion:	4.0
+Contact:	Jacek Anaszewski <j.anaszewski@samsung.com>
+Description:	read/write
+		Hardware timeout for flash, in microseconds. The flash strobe
+		is stopped after this period of time has passed from the start
+		of the strobe. The file is created only for the flash LED
+		devices that support setting flash timeout.
+
+What:		/sys/class/leds/<led>/max_flash_timeout
+Date:		March 2015
+KernelVersion:	4.0
+Contact:	Jacek Anaszewski <j.anaszewski@samsung.com>
+Description:	read only
+		Maximum flash timeout for this LED, in microseconds.
+
+What:		/sys/class/leds/<led>/flash_strobe
+Date:		March 2015
+KernelVersion:	4.0
+Contact:	Jacek Anaszewski <j.anaszewski@samsung.com>
+Description:	read/write
+		Flash strobe state. When written with 1 it triggers flash strobe
+		and when written with 0 it turns the flash off.
+
+		On read 1 means that flash is currently strobing and 0 means
+		that flash is off.
+
+What:		/sys/class/leds/<led>/flash_fault
+Date:		March 2015
+KernelVersion:	4.0
+Contact:	Jacek Anaszewski <j.anaszewski@samsung.com>
+Description:	read only
+		Space separated list of flash faults that may have occurred.
+		Flash faults are re-read after strobing the flash. Possible
+		flash faults:
+
+		* led-over-voltage
+			flash controller voltage to the flash LED
+			has exceeded the limit specific to the flash controller
+		* flash-timeout-exceeded
+			the flash strobe was still on when
+			the timeout set by the user has expired; not all flash
+			controllers may set this in all such conditions
+		* controller-over-temperature
+			the flash controller has
+			overheated
+		* controller-short-circuit
+			the short circuit protection
+			of the flash controller has been triggered
+		* led-power-supply-over-current
+			current in the LED power
+			supply has exceeded the limit specific to the flash
+			controller
+		* indicator-led-fault
+			the flash controller has detected
+			a short or open circuit condition on the indicator LED
+		* led-under-voltage
+			flash controller voltage to the flash
+			LED has been below the minimum limit specific to
+			the flash
+		* controller-under-voltage
+			the input voltage of the flash
+			controller is below the limit under which strobing the
+			flash at full current will not be possible;
+			the condition persists until this flag is no longer set
+		* led-over-temperature
+			the temperature of the LED has exceeded
+			its allowed upper limit