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, 56 insertions, 0 deletions

diff --git a/tools/perf/tests/bitmap.c b/tools/perf/tests/bitmap.c
new file mode 100644
index 000000000..e7adf60be
--- /dev/null
+++ b/tools/perf/tests/bitmap.c
@@ -0,0 +1,56 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/compiler.h>
+#include <linux/bitmap.h>
+#include <perf/cpumap.h>
+#include <internal/cpumap.h>
+#include "tests.h"
+#include "debug.h"
+
+#define NBITS 100
+
+static unsigned long *get_bitmap(const char *str, int nbits)
+{
+	struct perf_cpu_map *map = perf_cpu_map__new(str);
+	unsigned long *bm;
+
+	bm = bitmap_zalloc(nbits);
+
+	if (map && bm) {
+		unsigned int i;
+		struct perf_cpu cpu;
+
+		perf_cpu_map__for_each_cpu(cpu, i, map)
+			__set_bit(cpu.cpu, bm);
+	}
+
+	perf_cpu_map__put(map);
+	return bm;
+}
+
+static int test_bitmap(const char *str)
+{
+	unsigned long *bm = get_bitmap(str, NBITS);
+	char buf[100];
+	int ret;
+
+	bitmap_scnprintf(bm, NBITS, buf, sizeof(buf));
+	pr_debug("bitmap: %s\n", buf);
+
+	ret = !strcmp(buf, str);
+	free(bm);
+	return ret;
+}
+
+static int test__bitmap_print(struct test_suite *test __maybe_unused, int subtest __maybe_unused)
+{
+	TEST_ASSERT_VAL("failed to convert map", test_bitmap("1"));
+	TEST_ASSERT_VAL("failed to convert map", test_bitmap("1,5"));
+	TEST_ASSERT_VAL("failed to convert map", test_bitmap("1,3,5,7,9,11,13,15,17,19,21-40"));
+	TEST_ASSERT_VAL("failed to convert map", test_bitmap("2-5"));
+	TEST_ASSERT_VAL("failed to convert map", test_bitmap("1,3-6,8-10,24,35-37"));
+	TEST_ASSERT_VAL("failed to convert map", test_bitmap("1,3-6,8-10,24,35-37"));
+	TEST_ASSERT_VAL("failed to convert map", test_bitmap("1-10,12-20,22-30,32-40"));
+	return 0;
+}
+
+DEFINE_SUITE("Print bitmap", bitmap_print);