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, 177 insertions, 0 deletions

diff --git a/net/wireless/tests/fragmentation.c b/net/wireless/tests/fragmentation.c
new file mode 100644
index 000000000..411fae18c
--- /dev/null
+++ b/net/wireless/tests/fragmentation.c
@@ -0,0 +1,177 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * KUnit tests for element fragmentation
+ *
+ * Copyright (C) 2023-2024 Intel Corporation
+ */
+#include <linux/ieee80211.h>
+#include <net/cfg80211.h>
+#include <kunit/test.h>
+
+static void defragment_0(struct kunit *test)
+{
+	ssize_t ret;
+	static const u8 input[] = {
+		[0] = WLAN_EID_EXTENSION,
+		[1] = 254,
+		[2] = WLAN_EID_EXT_EHT_MULTI_LINK,
+		[27] = 27,
+		[123] = 123,
+		[254 + 2] = WLAN_EID_FRAGMENT,
+		[254 + 3] = 7,
+		[254 + 3 + 7] = 0, /* for size */
+	};
+	u8 *data = kunit_kzalloc(test, sizeof(input), GFP_KERNEL);
+
+	KUNIT_ASSERT_NOT_NULL(test, data);
+
+	ret = cfg80211_defragment_element((void *)input,
+					  input, sizeof(input),
+					  NULL, 0,
+					  WLAN_EID_FRAGMENT);
+	KUNIT_EXPECT_EQ(test, ret, 253);
+	ret = cfg80211_defragment_element((void *)input,
+					  input, sizeof(input),
+					  data, ret,
+					  WLAN_EID_FRAGMENT);
+	KUNIT_EXPECT_EQ(test, ret, 253);
+	KUNIT_EXPECT_MEMEQ(test, data, input + 3, 253);
+}
+
+static void defragment_1(struct kunit *test)
+{
+	ssize_t ret;
+	static const u8 input[] = {
+		[0] = WLAN_EID_EXTENSION,
+		[1] = 255,
+		[2] = WLAN_EID_EXT_EHT_MULTI_LINK,
+		[27] = 27,
+		[123] = 123,
+		[255 + 2] = WLAN_EID_FRAGMENT,
+		[255 + 3] = 7,
+		[255 + 3 + 1] = 0xaa,
+		[255 + 3 + 8] = WLAN_EID_FRAGMENT, /* not used */
+		[255 + 3 + 9] = 1,
+		[255 + 3 + 10] = 0, /* for size */
+	};
+	u8 *data = kunit_kzalloc(test, sizeof(input), GFP_KERNEL);
+	const struct element *elem;
+	int count = 0;
+
+	KUNIT_ASSERT_NOT_NULL(test, data);
+
+	for_each_element(elem, input, sizeof(input))
+		count++;
+
+	/* check the elements are right */
+	KUNIT_ASSERT_EQ(test, count, 3);
+
+	ret = cfg80211_defragment_element((void *)input,
+					  input, sizeof(input),
+					  NULL, 0,
+					  WLAN_EID_FRAGMENT);
+	KUNIT_EXPECT_EQ(test, ret, 254 + 7);
+	ret = cfg80211_defragment_element((void *)input,
+					  input, sizeof(input),
+					  data, ret,
+					  WLAN_EID_FRAGMENT);
+	/* this means the last fragment was not used */
+	KUNIT_EXPECT_EQ(test, ret, 254 + 7);
+	KUNIT_EXPECT_MEMEQ(test, data, input + 3, 254);
+	KUNIT_EXPECT_MEMEQ(test, data + 254, input + 255 + 4, 7);
+}
+
+static void defragment_2(struct kunit *test)
+{
+	ssize_t ret;
+	static const u8 input[] = {
+		[0] = WLAN_EID_EXTENSION,
+		[1] = 255,
+		[2] = WLAN_EID_EXT_EHT_MULTI_LINK,
+		[27] = 27,
+		[123] = 123,
+
+		[257 + 0] = WLAN_EID_FRAGMENT,
+		[257 + 1] = 255,
+		[257 + 20] = 0xaa,
+
+		[2 * 257 + 0] = WLAN_EID_FRAGMENT,
+		[2 * 257 + 1] = 1,
+		[2 * 257 + 2] = 0xcc,
+		[2 * 257 + 3] = WLAN_EID_FRAGMENT, /* not used */
+		[2 * 257 + 4] = 1,
+		[2 * 257 + 5] = 0, /* for size */
+	};
+	u8 *data = kunit_kzalloc(test, sizeof(input), GFP_KERNEL);
+	const struct element *elem;
+	int count = 0;
+
+	KUNIT_ASSERT_NOT_NULL(test, data);
+
+	for_each_element(elem, input, sizeof(input))
+		count++;
+
+	/* check the elements are right */
+	KUNIT_ASSERT_EQ(test, count, 4);
+
+	ret = cfg80211_defragment_element((void *)input,
+					  input, sizeof(input),
+					  NULL, 0,
+					  WLAN_EID_FRAGMENT);
+	/* this means the last fragment was not used */
+	KUNIT_EXPECT_EQ(test, ret, 254 + 255 + 1);
+	ret = cfg80211_defragment_element((void *)input,
+					  input, sizeof(input),
+					  data, ret,
+					  WLAN_EID_FRAGMENT);
+	KUNIT_EXPECT_EQ(test, ret, 254 + 255 + 1);
+	KUNIT_EXPECT_MEMEQ(test, data, input + 3, 254);
+	KUNIT_EXPECT_MEMEQ(test, data + 254, input + 257 + 2, 255);
+	KUNIT_EXPECT_MEMEQ(test, data + 254 + 255, input + 2 * 257 + 2, 1);
+}
+
+static void defragment_at_end(struct kunit *test)
+{
+	ssize_t ret;
+	static const u8 input[] = {
+		[0] = WLAN_EID_EXTENSION,
+		[1] = 255,
+		[2] = WLAN_EID_EXT_EHT_MULTI_LINK,
+		[27] = 27,
+		[123] = 123,
+		[255 + 2] = WLAN_EID_FRAGMENT,
+		[255 + 3] = 7,
+		[255 + 3 + 7] = 0, /* for size */
+	};
+	u8 *data = kunit_kzalloc(test, sizeof(input), GFP_KERNEL);
+
+	KUNIT_ASSERT_NOT_NULL(test, data);
+
+	ret = cfg80211_defragment_element((void *)input,
+					  input, sizeof(input),
+					  NULL, 0,
+					  WLAN_EID_FRAGMENT);
+	KUNIT_EXPECT_EQ(test, ret, 254 + 7);
+	ret = cfg80211_defragment_element((void *)input,
+					  input, sizeof(input),
+					  data, ret,
+					  WLAN_EID_FRAGMENT);
+	KUNIT_EXPECT_EQ(test, ret, 254 + 7);
+	KUNIT_EXPECT_MEMEQ(test, data, input + 3, 254);
+	KUNIT_EXPECT_MEMEQ(test, data + 254, input + 255 + 4, 7);
+}
+
+static struct kunit_case element_fragmentation_test_cases[] = {
+	KUNIT_CASE(defragment_0),
+	KUNIT_CASE(defragment_1),
+	KUNIT_CASE(defragment_2),
+	KUNIT_CASE(defragment_at_end),
+	{}
+};
+
+static struct kunit_suite element_fragmentation = {
+	.name = "cfg80211-element-defragmentation",
+	.test_cases = element_fragmentation_test_cases,
+};
+
+kunit_test_suite(element_fragmentation);