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, 95 insertions, 0 deletions

diff --git a/include/media/dvb_net.h b/include/media/dvb_net.h
new file mode 100644
index 000000000..4a921ea96
--- /dev/null
+++ b/include/media/dvb_net.h
@@ -0,0 +1,95 @@
+/*
+ * dvb_net.h
+ *
+ * Copyright (C) 2001 Ralph Metzler for convergence integrated media GmbH
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public License
+ * as published by the Free Software Foundation; either version 2.1
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ */
+
+#ifndef _DVB_NET_H_
+#define _DVB_NET_H_
+
+#include <linux/module.h>
+
+#include <media/dvbdev.h>
+
+struct net_device;
+
+#define DVB_NET_DEVICES_MAX 10
+
+#ifdef CONFIG_DVB_NET
+
+/**
+ * struct dvb_net - describes a DVB network interface
+ *
+ * @dvbdev:		pointer to &struct dvb_device.
+ * @device:		array of pointers to &struct net_device.
+ * @state:		array of integers to each net device. A value
+ *			different than zero means that the interface is
+ *			in usage.
+ * @exit:		flag to indicate when the device is being removed.
+ * @demux:		pointer to &struct dmx_demux.
+ * @ioctl_mutex:	protect access to this struct.
+ * @remove_mutex:	mutex that avoids a race condition between a callback
+ *			called when the hardware is disconnected and the
+ *			file_operations of dvb_net.
+ *
+ * Currently, the core supports up to %DVB_NET_DEVICES_MAX (10) network
+ * devices.
+ */
+
+struct dvb_net {
+	struct dvb_device *dvbdev;
+	struct net_device *device[DVB_NET_DEVICES_MAX];
+	int state[DVB_NET_DEVICES_MAX];
+	unsigned int exit:1;
+	struct dmx_demux *demux;
+	struct mutex ioctl_mutex;
+	struct mutex remove_mutex;
+};
+
+/**
+ * dvb_net_init - nitializes a digital TV network device and registers it.
+ *
+ * @adap:	pointer to &struct dvb_adapter.
+ * @dvbnet:	pointer to &struct dvb_net.
+ * @dmxdemux:	pointer to &struct dmx_demux.
+ */
+int dvb_net_init(struct dvb_adapter *adap, struct dvb_net *dvbnet,
+		  struct dmx_demux *dmxdemux);
+
+/**
+ * dvb_net_release - releases a digital TV network device and unregisters it.
+ *
+ * @dvbnet:	pointer to &struct dvb_net.
+ */
+void dvb_net_release(struct dvb_net *dvbnet);
+
+#else
+
+struct dvb_net {
+	struct dvb_device *dvbdev;
+};
+
+static inline void dvb_net_release(struct dvb_net *dvbnet)
+{
+}
+
+static inline int dvb_net_init(struct dvb_adapter *adap,
+			       struct dvb_net *dvbnet, struct dmx_demux *dmx)
+{
+	return 0;
+}
+
+#endif /* ifdef CONFIG_DVB_NET */
+
+#endif