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, 91 insertions, 0 deletions

diff --git a/drivers/mfd/act8945a.c b/drivers/mfd/act8945a.c
new file mode 100644
index 000000000..cafefb445
--- /dev/null
+++ b/drivers/mfd/act8945a.c
@@ -0,0 +1,91 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * MFD driver for Active-semi ACT8945a PMIC
+ *
+ * Copyright (C) 2015 Atmel Corporation.
+ *
+ * Author: Wenyou Yang <wenyou.yang@atmel.com>
+ */
+
+#include <linux/i2c.h>
+#include <linux/mfd/core.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/regmap.h>
+
+static const struct mfd_cell act8945a_devs[] = {
+	{
+		.name = "act8945a-regulator",
+	},
+	{
+		.name = "act8945a-charger",
+		.of_compatible = "active-semi,act8945a-charger",
+	},
+};
+
+static const struct regmap_config act8945a_regmap_config = {
+	.reg_bits = 8,
+	.val_bits = 8,
+};
+
+static int act8945a_i2c_probe(struct i2c_client *i2c)
+{
+	int ret;
+	struct regmap *regmap;
+
+	regmap = devm_regmap_init_i2c(i2c, &act8945a_regmap_config);
+	if (IS_ERR(regmap)) {
+		ret = PTR_ERR(regmap);
+		dev_err(&i2c->dev, "regmap init failed: %d\n", ret);
+		return ret;
+	}
+
+	i2c_set_clientdata(i2c, regmap);
+
+	ret = devm_mfd_add_devices(&i2c->dev, PLATFORM_DEVID_NONE,
+				   act8945a_devs, ARRAY_SIZE(act8945a_devs),
+				   NULL, 0, NULL);
+	if (ret) {
+		dev_err(&i2c->dev, "Failed to add sub devices\n");
+		return ret;
+	}
+
+	return 0;
+}
+
+static const struct i2c_device_id act8945a_i2c_id[] = {
+	{ "act8945a" },
+	{}
+};
+MODULE_DEVICE_TABLE(i2c, act8945a_i2c_id);
+
+static const struct of_device_id act8945a_of_match[] = {
+	{ .compatible = "active-semi,act8945a", },
+	{},
+};
+MODULE_DEVICE_TABLE(of, act8945a_of_match);
+
+static struct i2c_driver act8945a_i2c_driver = {
+	.driver = {
+		   .name = "act8945a",
+		   .of_match_table = act8945a_of_match,
+	},
+	.probe = act8945a_i2c_probe,
+	.id_table = act8945a_i2c_id,
+};
+
+static int __init act8945a_i2c_init(void)
+{
+	return i2c_add_driver(&act8945a_i2c_driver);
+}
+subsys_initcall(act8945a_i2c_init);
+
+static void __exit act8945a_i2c_exit(void)
+{
+	i2c_del_driver(&act8945a_i2c_driver);
+}
+module_exit(act8945a_i2c_exit);
+
+MODULE_DESCRIPTION("ACT8945A PMIC multi-function driver");
+MODULE_AUTHOR("Wenyou Yang <wenyou.yang@atmel.com>");
+MODULE_LICENSE("GPL");