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, 50 insertions, 0 deletions

diff --git a/Documentation/ABI/testing/sysfs-block-loop b/Documentation/ABI/testing/sysfs-block-loop
new file mode 100644
index 000000000..627f4eb87
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-block-loop
@@ -0,0 +1,50 @@
+What:		/sys/block/loopX/loop/autoclear
+Date:		Aug, 2010
+KernelVersion:	v2.6.37
+Contact:	linux-block@vger.kernel.org
+Description:
+		(RO) Shows if the device is in autoclear mode or not ( "1" or
+		"0"). Autoclear (if set) indicates that the loopback device will
+		self-distruct after last close.
+
+What:		/sys/block/loopX/loop/backing_file
+Date:		Aug, 2010
+KernelVersion:	v2.6.37
+Contact:	linux-block@vger.kernel.org
+Description:
+		(RO) The path of the backing file that the loop device maps its
+		data blocks to.
+
+What:		/sys/block/loopX/loop/offset
+Date:		Aug, 2010
+KernelVersion:	v2.6.37
+Contact:	linux-block@vger.kernel.org
+Description:
+		(RO) Start offset (in bytes).
+
+What:		/sys/block/loopX/loop/sizelimit
+Date:		Aug, 2010
+KernelVersion:	v2.6.37
+Contact:	linux-block@vger.kernel.org
+Description:
+		(RO) The size (in bytes) that the block device maps, starting
+		from the offset.
+
+What:		/sys/block/loopX/loop/partscan
+Date:		Aug, 2011
+KernelVersion:	v3.10
+Contact:	linux-block@vger.kernel.org
+Description:
+		(RO) Shows if automatic partition scanning is enabled for the
+		device or not ("1" or "0"). This can be requested individually
+		per loop device during its setup by setting LO_FLAGS_PARTSCAN in
+		in the ioctl request. By default, no partition tables are
+		scanned.
+
+What:		/sys/block/loopX/loop/dio
+Date:		Aug, 2015
+KernelVersion:	v4.10
+Contact:	linux-block@vger.kernel.org
+Description:
+		(RO) Shows if direct IO is being used to access backing file or
+		not ("1 or "0").