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, 19 insertions, 0 deletions

diff --git a/scripts/checker-valid.sh b/scripts/checker-valid.sh
new file mode 100755
index 000000000..625a789ed
--- /dev/null
+++ b/scripts/checker-valid.sh
@@ -0,0 +1,19 @@
+#!/bin/sh -eu
+# SPDX-License-Identifier: GPL-2.0
+
+[ ! -x "$(command -v "$1")" ] && exit 1
+
+tmp_file=$(mktemp)
+trap "rm -f $tmp_file" EXIT
+
+cat << EOF >$tmp_file
+static inline int u(const int *q)
+{
+	__typeof_unqual__(*q) v = *q;
+	return v;
+}
+EOF
+
+# sparse happily exits with 0 on error so validate
+# there is none on stderr. Use awk as grep is a pain with sh -e
+$@ $tmp_file 2>&1 | awk -v c=1 '/error/{c=0}END{print c}'