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, 90 insertions, 0 deletions

diff --git a/drivers/firewire/uapi-test.c b/drivers/firewire/uapi-test.c
new file mode 100644
index 000000000..bc3f10a2e
--- /dev/null
+++ b/drivers/firewire/uapi-test.c
@@ -0,0 +1,90 @@
+// SPDX-License-Identifier: GPL-2.0-only
+//
+// uapi_test.c - An application of Kunit to check layout of structures exposed to user space for
+//		 FireWire subsystem.
+//
+// Copyright (c) 2023 Takashi Sakamoto
+
+#include <kunit/test.h>
+#include <linux/firewire-cdev.h>
+
+// Known issue added at v2.6.27 kernel.
+static void structure_layout_event_response(struct kunit *test)
+{
+#if defined(CONFIG_X86_32)
+	// 4 bytes alignment for aggregate type including 8 bytes storage types.
+	KUNIT_EXPECT_EQ(test, 20, sizeof(struct fw_cdev_event_response));
+#else
+	// 8 bytes alignment for aggregate type including 8 bytes storage types.
+	KUNIT_EXPECT_EQ(test, 24, sizeof(struct fw_cdev_event_response));
+#endif
+
+	KUNIT_EXPECT_EQ(test, 0, offsetof(struct fw_cdev_event_response, closure));
+	KUNIT_EXPECT_EQ(test, 8, offsetof(struct fw_cdev_event_response, type));
+	KUNIT_EXPECT_EQ(test, 12, offsetof(struct fw_cdev_event_response, rcode));
+	KUNIT_EXPECT_EQ(test, 16, offsetof(struct fw_cdev_event_response, length));
+	KUNIT_EXPECT_EQ(test, 20, offsetof(struct fw_cdev_event_response, data));
+}
+
+// Added at v6.5.
+static void structure_layout_event_request3(struct kunit *test)
+{
+	KUNIT_EXPECT_EQ(test, 56, sizeof(struct fw_cdev_event_request3));
+
+	KUNIT_EXPECT_EQ(test, 0, offsetof(struct fw_cdev_event_request3, closure));
+	KUNIT_EXPECT_EQ(test, 8, offsetof(struct fw_cdev_event_request3, type));
+	KUNIT_EXPECT_EQ(test, 12, offsetof(struct fw_cdev_event_request3, tcode));
+	KUNIT_EXPECT_EQ(test, 16, offsetof(struct fw_cdev_event_request3, offset));
+	KUNIT_EXPECT_EQ(test, 24, offsetof(struct fw_cdev_event_request3, source_node_id));
+	KUNIT_EXPECT_EQ(test, 28, offsetof(struct fw_cdev_event_request3, destination_node_id));
+	KUNIT_EXPECT_EQ(test, 32, offsetof(struct fw_cdev_event_request3, card));
+	KUNIT_EXPECT_EQ(test, 36, offsetof(struct fw_cdev_event_request3, generation));
+	KUNIT_EXPECT_EQ(test, 40, offsetof(struct fw_cdev_event_request3, handle));
+	KUNIT_EXPECT_EQ(test, 44, offsetof(struct fw_cdev_event_request3, length));
+	KUNIT_EXPECT_EQ(test, 48, offsetof(struct fw_cdev_event_request3, tstamp));
+	KUNIT_EXPECT_EQ(test, 56, offsetof(struct fw_cdev_event_request3, data));
+}
+
+// Added at v6.5.
+static void structure_layout_event_response2(struct kunit *test)
+{
+	KUNIT_EXPECT_EQ(test, 32, sizeof(struct fw_cdev_event_response2));
+
+	KUNIT_EXPECT_EQ(test, 0, offsetof(struct fw_cdev_event_response2, closure));
+	KUNIT_EXPECT_EQ(test, 8, offsetof(struct fw_cdev_event_response2, type));
+	KUNIT_EXPECT_EQ(test, 12, offsetof(struct fw_cdev_event_response2, rcode));
+	KUNIT_EXPECT_EQ(test, 16, offsetof(struct fw_cdev_event_response2, length));
+	KUNIT_EXPECT_EQ(test, 20, offsetof(struct fw_cdev_event_response2, request_tstamp));
+	KUNIT_EXPECT_EQ(test, 24, offsetof(struct fw_cdev_event_response2, response_tstamp));
+	KUNIT_EXPECT_EQ(test, 32, offsetof(struct fw_cdev_event_response2, data));
+}
+
+// Added at v6.5.
+static void structure_layout_event_phy_packet2(struct kunit *test)
+{
+	KUNIT_EXPECT_EQ(test, 24, sizeof(struct fw_cdev_event_phy_packet2));
+
+	KUNIT_EXPECT_EQ(test, 0, offsetof(struct fw_cdev_event_phy_packet2, closure));
+	KUNIT_EXPECT_EQ(test, 8, offsetof(struct fw_cdev_event_phy_packet2, type));
+	KUNIT_EXPECT_EQ(test, 12, offsetof(struct fw_cdev_event_phy_packet2, rcode));
+	KUNIT_EXPECT_EQ(test, 16, offsetof(struct fw_cdev_event_phy_packet2, length));
+	KUNIT_EXPECT_EQ(test, 20, offsetof(struct fw_cdev_event_phy_packet2, tstamp));
+	KUNIT_EXPECT_EQ(test, 24, offsetof(struct fw_cdev_event_phy_packet2, data));
+}
+
+static struct kunit_case structure_layout_test_cases[] = {
+	KUNIT_CASE(structure_layout_event_response),
+	KUNIT_CASE(structure_layout_event_request3),
+	KUNIT_CASE(structure_layout_event_response2),
+	KUNIT_CASE(structure_layout_event_phy_packet2),
+	{}
+};
+
+static struct kunit_suite structure_layout_test_suite = {
+	.name = "firewire-uapi-structure-layout",
+	.test_cases = structure_layout_test_cases,
+};
+kunit_test_suite(structure_layout_test_suite);
+
+MODULE_DESCRIPTION("FireWire UAPI unit test suite");
+MODULE_LICENSE("GPL");