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, 26 insertions, 0 deletions

diff --git a/scripts/modules-check.sh b/scripts/modules-check.sh
new file mode 100755
index 000000000..4c8da90de
--- /dev/null
+++ b/scripts/modules-check.sh
@@ -0,0 +1,26 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0
+
+set -e
+
+if [ $# != 1 ]; then
+	echo "Usage: $0 <modules.order>" >& 2
+	exit 1
+fi
+
+exit_code=0
+
+# Check uniqueness of module names
+check_same_name_modules()
+{
+	for m in $(sed 's:.*/::' "$1" | sort | uniq -d)
+	do
+		echo "error: the following would cause module name conflict:" >&2
+		sed -n "/\/$m/s:^\(.*\)\.o\$:  \1.ko:p" "$1" >&2
+		exit_code=1
+	done
+}
+
+check_same_name_modules "$1"
+
+exit $exit_code