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, 33 insertions, 0 deletions

diff --git a/lib/kunit/hooks-impl.h b/lib/kunit/hooks-impl.h
new file mode 100644
index 000000000..d8720f261
--- /dev/null
+++ b/lib/kunit/hooks-impl.h
@@ -0,0 +1,33 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Declarations for hook implementations.
+ *
+ * These will be set as the function pointers in struct kunit_hook_table,
+ * found in include/kunit/test-bug.h.
+ *
+ * Copyright (C) 2023, Google LLC.
+ * Author: David Gow <davidgow@google.com>
+ */
+
+#ifndef _KUNIT_HOOKS_IMPL_H
+#define _KUNIT_HOOKS_IMPL_H
+
+#include <kunit/test-bug.h>
+
+/* List of declarations. */
+void __printf(3, 4) __kunit_fail_current_test_impl(const char *file,
+						   int line,
+						   const char *fmt, ...);
+void *__kunit_get_static_stub_address_impl(struct kunit *test, void *real_fn_addr);
+bool __kunit_is_suppressed_warning_impl(bool count);
+
+/* Code to set all of the function pointers. */
+static inline void kunit_install_hooks(void)
+{
+	/* Install the KUnit hook functions. */
+	kunit_hooks.fail_current_test = __kunit_fail_current_test_impl;
+	kunit_hooks.get_static_stub_address = __kunit_get_static_stub_address_impl;
+	kunit_hooks.is_suppressed_warning = __kunit_is_suppressed_warning_impl;
+}
+
+#endif /* _KUNIT_HOOKS_IMPL_H */