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, 69 insertions, 0 deletions

diff --git a/include/drm/drm_util.h b/include/drm/drm_util.h
new file mode 100644
index 000000000..440199618
--- /dev/null
+++ b/include/drm/drm_util.h
@@ -0,0 +1,69 @@
+/*
+ * Internal Header for the Direct Rendering Manager
+ *
+ * Copyright 2018 Intel Corporation
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * VA LINUX SYSTEMS AND/OR ITS SUPPLIERS BE LIABLE FOR ANY CLAIM, DAMAGES OR
+ * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
+ * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
+ * OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+#ifndef _DRM_UTIL_H_
+#define _DRM_UTIL_H_
+
+/**
+ * DOC: drm utils
+ *
+ * Macros and inline functions that does not naturally belong in other places
+ */
+
+#include <linux/interrupt.h>
+#include <linux/kgdb.h>
+#include <linux/preempt.h>
+#include <linux/smp.h>
+#include <linux/util_macros.h>
+
+/*
+ * Use EXPORT_SYMBOL_FOR_TESTS_ONLY() for functions that shall
+ * only be visible for drmselftests.
+ */
+#if defined(CONFIG_DRM_EXPORT_FOR_TESTS)
+#define EXPORT_SYMBOL_FOR_TESTS_ONLY(x) EXPORT_SYMBOL(x)
+#else
+#define EXPORT_SYMBOL_FOR_TESTS_ONLY(x)
+#endif
+
+/**
+ * drm_can_sleep - returns true if currently okay to sleep
+ *
+ * This function shall not be used in new code.
+ * The check for running in atomic context may not work - see linux/preempt.h.
+ *
+ * FIXME: All users of drm_can_sleep should be removed (see todo.rst)
+ *
+ * Returns:
+ * False if kgdb is active, we are in atomic context or irqs are disabled.
+ */
+static inline bool drm_can_sleep(void)
+{
+	if (in_atomic() || in_dbg_master() || irqs_disabled())
+		return false;
+	return true;
+}
+
+#endif