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, 82 insertions, 0 deletions

diff --git a/drivers/dio/dio-sysfs.c b/drivers/dio/dio-sysfs.c
new file mode 100644
index 000000000..ee1a3b59b
--- /dev/null
+++ b/drivers/dio/dio-sysfs.c
@@ -0,0 +1,82 @@
+/*
+ *  File Attributes for DIO Devices
+ *
+ *  Copyright (C) 2004 Jochen Friedrich
+ *
+ *  Loosely based on drivers/pci/pci-sysfs.c and drivers/zorro/zorro-sysfs.c
+ *
+ *  This file is subject to the terms and conditions of the GNU General Public
+ *  License.  See the file COPYING in the main directory of this archive
+ *  for more details.
+ */
+
+
+#include <linux/kernel.h>
+#include <linux/dio.h>
+#include <linux/stat.h>
+
+/* show configuration fields */
+
+static ssize_t dio_show_id(struct device *dev, struct device_attribute *attr, char *buf)
+{
+	struct dio_dev *d;
+
+	d = to_dio_dev(dev);
+	return sprintf(buf, "0x%02x\n", (d->id & 0xff));
+}
+static DEVICE_ATTR(id, S_IRUGO, dio_show_id, NULL);
+
+static ssize_t dio_show_ipl(struct device *dev, struct device_attribute *attr, char *buf)
+{
+	struct dio_dev *d;
+
+	d = to_dio_dev(dev);
+	return sprintf(buf, "0x%02x\n", d->ipl);
+}
+static DEVICE_ATTR(ipl, S_IRUGO, dio_show_ipl, NULL);
+
+static ssize_t dio_show_secid(struct device *dev, struct device_attribute *attr, char *buf)
+{
+	struct dio_dev *d;
+
+	d = to_dio_dev(dev);
+	return sprintf(buf, "0x%02x\n", ((d->id >> 8)& 0xff));
+}
+static DEVICE_ATTR(secid, S_IRUGO, dio_show_secid, NULL);
+
+static ssize_t dio_show_name(struct device *dev, struct device_attribute *attr, char *buf)
+{
+	struct dio_dev *d;
+
+	d = to_dio_dev(dev);
+	return sprintf(buf, "%s\n", d->name);
+}
+static DEVICE_ATTR(name, S_IRUGO, dio_show_name, NULL);
+
+static ssize_t dio_show_resource(struct device *dev, struct device_attribute *attr, char *buf)
+{
+	struct dio_dev *d = to_dio_dev(dev);
+
+	return sprintf(buf, "0x%08lx 0x%08lx 0x%08lx\n",
+		       (unsigned long)dio_resource_start(d),
+		       (unsigned long)dio_resource_end(d),
+		       dio_resource_flags(d));
+}
+static DEVICE_ATTR(resource, S_IRUGO, dio_show_resource, NULL);
+
+int dio_create_sysfs_dev_files(struct dio_dev *d)
+{
+	struct device *dev = &d->dev;
+	int error;
+
+	/* current configuration's attributes */
+	if ((error = device_create_file(dev, &dev_attr_id)) ||
+	    (error = device_create_file(dev, &dev_attr_ipl)) ||
+	    (error = device_create_file(dev, &dev_attr_secid)) ||
+	    (error = device_create_file(dev, &dev_attr_name)) ||
+	    (error = device_create_file(dev, &dev_attr_resource)))
+		return error;
+
+	return 0;
+}
+