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, 143 insertions, 0 deletions

diff --git a/lib/tests/liveupdate.c b/lib/tests/liveupdate.c
new file mode 100644
index 000000000..4c08a7c6f
--- /dev/null
+++ b/lib/tests/liveupdate.c
@@ -0,0 +1,143 @@
+// SPDX-License-Identifier: GPL-2.0
+
+/*
+ * Copyright (c) 2025, Google LLC.
+ * Pasha Tatashin <pasha.tatashin@soleen.com>
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME " test: " fmt
+
+#include <linux/cleanup.h>
+#include <linux/errno.h>
+#include <linux/init.h>
+#include <linux/liveupdate.h>
+#include <linux/module.h>
+#include "../../kernel/liveupdate/luo_internal.h"
+
+static const struct liveupdate_flb_ops test_flb_ops;
+#define DEFINE_TEST_FLB(i) {						\
+	.ops = &test_flb_ops,						\
+	.compatible = LIVEUPDATE_TEST_FLB_COMPATIBLE(i),		\
+}
+
+/* Number of Test FLBs to register with every file handler */
+#define TEST_NFLBS 3
+static struct liveupdate_flb test_flbs[TEST_NFLBS] = {
+	DEFINE_TEST_FLB(0),
+	DEFINE_TEST_FLB(1),
+	DEFINE_TEST_FLB(2),
+};
+
+#define TEST_FLB_MAGIC_BASE 0xFEEDF00DCAFEBEE0ULL
+
+static int test_flb_preserve(struct liveupdate_flb_op_args *argp)
+{
+	ptrdiff_t index = argp->flb - test_flbs;
+
+	pr_info("%s: preserve was triggered\n", argp->flb->compatible);
+	argp->data = TEST_FLB_MAGIC_BASE + index;
+
+	return 0;
+}
+
+static void test_flb_unpreserve(struct liveupdate_flb_op_args *argp)
+{
+	pr_info("%s: unpreserve was triggered\n", argp->flb->compatible);
+}
+
+static int test_flb_retrieve(struct liveupdate_flb_op_args *argp)
+{
+	ptrdiff_t index = argp->flb - test_flbs;
+	u64 expected_data = TEST_FLB_MAGIC_BASE + index;
+
+	if (argp->data == expected_data) {
+		pr_info("%s: found flb data from the previous boot\n",
+			argp->flb->compatible);
+		argp->obj = (void *)argp->data;
+	} else {
+		pr_err("%s: ERROR - incorrect data handle: %llx, expected %llx\n",
+		       argp->flb->compatible, argp->data, expected_data);
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static void test_flb_finish(struct liveupdate_flb_op_args *argp)
+{
+	ptrdiff_t index = argp->flb - test_flbs;
+	void *expected_obj = (void *)(TEST_FLB_MAGIC_BASE + index);
+
+	if (argp->obj == expected_obj) {
+		pr_info("%s: finish was triggered\n", argp->flb->compatible);
+	} else {
+		pr_err("%s: ERROR - finish called with invalid object\n",
+		       argp->flb->compatible);
+	}
+}
+
+static const struct liveupdate_flb_ops test_flb_ops = {
+	.preserve	= test_flb_preserve,
+	.unpreserve	= test_flb_unpreserve,
+	.retrieve	= test_flb_retrieve,
+	.finish		= test_flb_finish,
+	.owner		= THIS_MODULE,
+};
+
+static void liveupdate_test_init(void)
+{
+	static DEFINE_MUTEX(init_lock);
+	static bool initialized;
+	int i;
+
+	guard(mutex)(&init_lock);
+
+	if (initialized)
+		return;
+
+	for (i = 0; i < TEST_NFLBS; i++) {
+		struct liveupdate_flb *flb = &test_flbs[i];
+		void *obj;
+		int err;
+
+		err = liveupdate_flb_get_incoming(flb, &obj);
+		if (err && err != -ENODATA && err != -ENOENT) {
+			pr_err("liveupdate_flb_get_incoming for %s failed: %pe\n",
+			       flb->compatible, ERR_PTR(err));
+		}
+
+		if (!err)
+			liveupdate_flb_put_incoming(flb);
+	}
+	initialized = true;
+}
+
+void liveupdate_test_register(struct liveupdate_file_handler *fh)
+{
+	int err, i;
+
+	liveupdate_test_init();
+
+	for (i = 0; i < TEST_NFLBS; i++) {
+		struct liveupdate_flb *flb = &test_flbs[i];
+
+		err = liveupdate_register_flb(fh, flb);
+		if (err) {
+			pr_err("Failed to register %s %pe\n",
+			       flb->compatible, ERR_PTR(err));
+		}
+	}
+
+	err = liveupdate_register_flb(fh, &test_flbs[0]);
+	if (!err || err != -EEXIST) {
+		pr_err("Failed: %s should be already registered, but got err: %pe\n",
+		       test_flbs[0].compatible, ERR_PTR(err));
+	}
+
+	pr_info("Registered %d FLBs with file handler: [%s]\n",
+		TEST_NFLBS, fh->compatible);
+}
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Pasha Tatashin <pasha.tatashin@soleen.com>");
+MODULE_DESCRIPTION("In-kernel test for LUO mechanism");