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, 134 insertions, 0 deletions

diff --git a/tools/perf/tests/subcmd-help.c b/tools/perf/tests/subcmd-help.c
new file mode 100644
index 000000000..9da96a16f
--- /dev/null
+++ b/tools/perf/tests/subcmd-help.c
@@ -0,0 +1,134 @@
+// SPDX-License-Identifier: GPL-2.0
+#include "tests.h"
+#include <linux/compiler.h>
+#include <subcmd/help.h>
+
+static int test__load_cmdnames(struct test_suite *test __maybe_unused,
+			       int subtest __maybe_unused)
+{
+	struct cmdnames cmds = {};
+
+	add_cmdname(&cmds, "aaa", 3);
+	add_cmdname(&cmds, "foo", 3);
+	add_cmdname(&cmds, "xyz", 3);
+
+	TEST_ASSERT_VAL("cannot find cmd", is_in_cmdlist(&cmds, "aaa") == 1);
+	TEST_ASSERT_VAL("wrong cmd", is_in_cmdlist(&cmds, "bar") == 0);
+	TEST_ASSERT_VAL("case sensitive", is_in_cmdlist(&cmds, "XYZ") == 0);
+
+	clean_cmdnames(&cmds);
+	return TEST_OK;
+}
+
+static int test__uniq_cmdnames(struct test_suite *test __maybe_unused,
+			       int subtest __maybe_unused)
+{
+	struct cmdnames cmds = {};
+
+	/* uniq() assumes it's sorted */
+	add_cmdname(&cmds, "aaa", 3);
+	add_cmdname(&cmds, "aaa", 3);
+	add_cmdname(&cmds, "bbb", 3);
+
+	TEST_ASSERT_VAL("invalid original size", cmds.cnt == 3);
+	/* uniquify command names (to remove second 'aaa') */
+	uniq(&cmds);
+	TEST_ASSERT_VAL("invalid final size", cmds.cnt == 2);
+
+	TEST_ASSERT_VAL("cannot find cmd", is_in_cmdlist(&cmds, "aaa") == 1);
+	TEST_ASSERT_VAL("cannot find cmd", is_in_cmdlist(&cmds, "bbb") == 1);
+	TEST_ASSERT_VAL("wrong cmd", is_in_cmdlist(&cmds, "ccc") == 0);
+
+	clean_cmdnames(&cmds);
+	return TEST_OK;
+}
+
+static int test__exclude_cmdnames(struct test_suite *test __maybe_unused,
+				  int subtest __maybe_unused)
+{
+	struct cmdnames cmds1 = {};
+	struct cmdnames cmds2 = {};
+
+	add_cmdname(&cmds1, "aaa", 3);
+	add_cmdname(&cmds1, "bbb", 3);
+	add_cmdname(&cmds1, "ccc", 3);
+	add_cmdname(&cmds1, "ddd", 3);
+	add_cmdname(&cmds1, "eee", 3);
+	add_cmdname(&cmds1, "fff", 3);
+	add_cmdname(&cmds1, "ggg", 3);
+	add_cmdname(&cmds1, "hhh", 3);
+	add_cmdname(&cmds1, "iii", 3);
+	add_cmdname(&cmds1, "jjj", 3);
+
+	add_cmdname(&cmds2, "bbb", 3);
+	add_cmdname(&cmds2, "eee", 3);
+	add_cmdname(&cmds2, "jjj", 3);
+
+	TEST_ASSERT_VAL("invalid original size", cmds1.cnt == 10);
+	TEST_ASSERT_VAL("invalid original size", cmds2.cnt == 3);
+
+	/* remove duplicate command names in cmds1 */
+	exclude_cmds(&cmds1, &cmds2);
+
+	TEST_ASSERT_VAL("invalid excluded size", cmds1.cnt == 7);
+	TEST_ASSERT_VAL("invalid excluded size", cmds2.cnt == 3);
+
+	/* excluded commands should not belong to cmds1 */
+	TEST_ASSERT_VAL("cannot find cmd", is_in_cmdlist(&cmds1, "aaa") == 1);
+	TEST_ASSERT_VAL("wrong cmd", is_in_cmdlist(&cmds1, "bbb") == 0);
+	TEST_ASSERT_VAL("cannot find cmd", is_in_cmdlist(&cmds1, "ccc") == 1);
+	TEST_ASSERT_VAL("cannot find cmd", is_in_cmdlist(&cmds1, "ddd") == 1);
+	TEST_ASSERT_VAL("wrong cmd", is_in_cmdlist(&cmds1, "eee") == 0);
+	TEST_ASSERT_VAL("cannot find cmd", is_in_cmdlist(&cmds1, "fff") == 1);
+	TEST_ASSERT_VAL("cannot find cmd", is_in_cmdlist(&cmds1, "ggg") == 1);
+	TEST_ASSERT_VAL("cannot find cmd", is_in_cmdlist(&cmds1, "hhh") == 1);
+	TEST_ASSERT_VAL("cannot find cmd", is_in_cmdlist(&cmds1, "iii") == 1);
+	TEST_ASSERT_VAL("wrong cmd", is_in_cmdlist(&cmds1, "jjj") == 0);
+
+	/* they should be only in cmds2 */
+	TEST_ASSERT_VAL("cannot find cmd", is_in_cmdlist(&cmds2, "bbb") == 1);
+	TEST_ASSERT_VAL("cannot find cmd", is_in_cmdlist(&cmds2, "eee") == 1);
+	TEST_ASSERT_VAL("cannot find cmd", is_in_cmdlist(&cmds2, "jjj") == 1);
+
+	clean_cmdnames(&cmds1);
+	clean_cmdnames(&cmds2);
+	return TEST_OK;
+}
+
+static int test__exclude_cmdnames_no_overlap(struct test_suite *test __maybe_unused,
+					     int subtest __maybe_unused)
+{
+	struct cmdnames cmds1 = {};
+	struct cmdnames cmds2 = {};
+
+	add_cmdname(&cmds1, "read-vdso32", 11);
+	add_cmdname(&cmds2, "archive", 7);
+
+	TEST_ASSERT_VAL("invalid original size", cmds1.cnt == 1);
+	TEST_ASSERT_VAL("invalid original size", cmds2.cnt == 1);
+
+	exclude_cmds(&cmds1, &cmds2);
+
+	TEST_ASSERT_VAL("invalid excluded size", cmds1.cnt == 1);
+	TEST_ASSERT_VAL("invalid excluded size", cmds2.cnt == 1);
+
+	TEST_ASSERT_VAL("cannot find cmd", is_in_cmdlist(&cmds1, "read-vdso32") == 1);
+	TEST_ASSERT_VAL("wrong cmd", is_in_cmdlist(&cmds1, "archive") == 0);
+
+	clean_cmdnames(&cmds1);
+	clean_cmdnames(&cmds2);
+	return TEST_OK;
+}
+
+static struct test_case tests__subcmd_help[] = {
+	TEST_CASE("Load subcmd names", load_cmdnames),
+	TEST_CASE("Uniquify subcmd names", uniq_cmdnames),
+	TEST_CASE("Exclude duplicate subcmd names", exclude_cmdnames),
+	TEST_CASE("Exclude disjoint subcmd names", exclude_cmdnames_no_overlap),
+	{	.name = NULL, }
+};
+
+struct test_suite suite__subcmd_help = {
+	.desc = "libsubcmd help tests",
+	.test_cases = tests__subcmd_help,
+};