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, 63 insertions, 0 deletions

diff --git a/include/media/media-dev-allocator.h b/include/media/media-dev-allocator.h
new file mode 100644
index 000000000..2ab54d426
--- /dev/null
+++ b/include/media/media-dev-allocator.h
@@ -0,0 +1,63 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ * media-dev-allocator.h - Media Controller Device Allocator API
+ *
+ * Copyright (c) 2019 Shuah Khan <shuah@kernel.org>
+ *
+ * Credits: Suggested by Laurent Pinchart <laurent.pinchart@ideasonboard.com>
+ */
+
+/*
+ * This file adds a global ref-counted Media Controller Device Instance API.
+ * A system wide global media device list is managed and each media device
+ * includes a kref count. The last put on the media device releases the media
+ * device instance.
+ */
+
+#ifndef _MEDIA_DEV_ALLOCATOR_H
+#define _MEDIA_DEV_ALLOCATOR_H
+
+struct usb_device;
+
+#if defined(CONFIG_MEDIA_CONTROLLER) && IS_ENABLED(CONFIG_USB)
+/**
+ * media_device_usb_allocate() - Allocate and return struct &media device
+ *
+ * @udev:		struct &usb_device pointer
+ * @module_name:	should be filled with %KBUILD_MODNAME
+ * @owner:		struct module pointer %THIS_MODULE for the driver.
+ *			%THIS_MODULE is null for a built-in driver.
+ *			It is safe even when %THIS_MODULE is null.
+ *
+ * This interface should be called to allocate a Media Device when multiple
+ * drivers share usb_device and the media device. This interface allocates
+ * &media_device structure and calls media_device_usb_init() to initialize
+ * it.
+ *
+ */
+struct media_device *media_device_usb_allocate(struct usb_device *udev,
+					       const char *module_name,
+					       struct module *owner);
+/**
+ * media_device_delete() - Release media device. Calls kref_put().
+ *
+ * @mdev:		struct &media_device pointer
+ * @module_name:	should be filled with %KBUILD_MODNAME
+ * @owner:		struct module pointer %THIS_MODULE for the driver.
+ *			%THIS_MODULE is null for a built-in driver.
+ *			It is safe even when %THIS_MODULE is null.
+ *
+ * This interface should be called to put Media Device Instance kref.
+ */
+void media_device_delete(struct media_device *mdev, const char *module_name,
+			 struct module *owner);
+#else
+static inline struct media_device *media_device_usb_allocate(
+			struct usb_device *udev, const char *module_name,
+			struct module *owner)
+			{ return NULL; }
+static inline void media_device_delete(
+			struct media_device *mdev, const char *module_name,
+			struct module *owner) { }
+#endif /* CONFIG_MEDIA_CONTROLLER && CONFIG_USB */
+#endif /* _MEDIA_DEV_ALLOCATOR_H */