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, 158 insertions, 0 deletions

diff --git a/drivers/rtc/rtc-em3027.c b/drivers/rtc/rtc-em3027.c
new file mode 100644
index 000000000..d555e5d59
--- /dev/null
+++ b/drivers/rtc/rtc-em3027.c
@@ -0,0 +1,158 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * An rtc/i2c driver for the EM Microelectronic EM3027
+ * Copyright 2011 CompuLab, Ltd.
+ *
+ * Author: Mike Rapoport <mike@compulab.co.il>
+ *
+ * Based on rtc-ds1672.c by Alessandro Zummo <a.zummo@towertech.it>
+ */
+
+#include <linux/i2c.h>
+#include <linux/rtc.h>
+#include <linux/bcd.h>
+#include <linux/module.h>
+#include <linux/of.h>
+
+/* Registers */
+#define EM3027_REG_ON_OFF_CTRL	0x00
+#define EM3027_REG_IRQ_CTRL	0x01
+#define EM3027_REG_IRQ_FLAGS	0x02
+#define EM3027_REG_STATUS	0x03
+#define EM3027_REG_RST_CTRL	0x04
+
+#define EM3027_REG_WATCH_SEC	0x08
+#define EM3027_REG_WATCH_MIN	0x09
+#define EM3027_REG_WATCH_HOUR	0x0a
+#define EM3027_REG_WATCH_DATE	0x0b
+#define EM3027_REG_WATCH_DAY	0x0c
+#define EM3027_REG_WATCH_MON	0x0d
+#define EM3027_REG_WATCH_YEAR	0x0e
+
+#define EM3027_REG_ALARM_SEC	0x10
+#define EM3027_REG_ALARM_MIN	0x11
+#define EM3027_REG_ALARM_HOUR	0x12
+#define EM3027_REG_ALARM_DATE	0x13
+#define EM3027_REG_ALARM_DAY	0x14
+#define EM3027_REG_ALARM_MON	0x15
+#define EM3027_REG_ALARM_YEAR	0x16
+
+static struct i2c_driver em3027_driver;
+
+static int em3027_get_time(struct device *dev, struct rtc_time *tm)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+
+	unsigned char addr = EM3027_REG_WATCH_SEC;
+	unsigned char buf[7];
+
+	struct i2c_msg msgs[] = {
+		{/* setup read addr */
+			.addr = client->addr,
+			.len = 1,
+			.buf = &addr
+		},
+		{/* read time/date */
+			.addr = client->addr,
+			.flags = I2C_M_RD,
+			.len = 7,
+			.buf = buf
+		},
+	};
+
+	/* read time/date registers */
+	if ((i2c_transfer(client->adapter, &msgs[0], 2)) != 2) {
+		dev_err(&client->dev, "%s: read error\n", __func__);
+		return -EIO;
+	}
+
+	tm->tm_sec	= bcd2bin(buf[0]);
+	tm->tm_min	= bcd2bin(buf[1]);
+	tm->tm_hour	= bcd2bin(buf[2]);
+	tm->tm_mday	= bcd2bin(buf[3]);
+	tm->tm_wday	= bcd2bin(buf[4]);
+	tm->tm_mon	= bcd2bin(buf[5]) - 1;
+	tm->tm_year	= bcd2bin(buf[6]) + 100;
+
+	return 0;
+}
+
+static int em3027_set_time(struct device *dev, struct rtc_time *tm)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	unsigned char buf[8];
+
+	struct i2c_msg msg = {
+		.addr = client->addr,
+		.len = 8,
+		.buf = buf,	/* write time/date */
+	};
+
+	buf[0] = EM3027_REG_WATCH_SEC;
+	buf[1] = bin2bcd(tm->tm_sec);
+	buf[2] = bin2bcd(tm->tm_min);
+	buf[3] = bin2bcd(tm->tm_hour);
+	buf[4] = bin2bcd(tm->tm_mday);
+	buf[5] = bin2bcd(tm->tm_wday);
+	buf[6] = bin2bcd(tm->tm_mon + 1);
+	buf[7] = bin2bcd(tm->tm_year % 100);
+
+	/* write time/date registers */
+	if ((i2c_transfer(client->adapter, &msg, 1)) != 1) {
+		dev_err(&client->dev, "%s: write error\n", __func__);
+		return -EIO;
+	}
+
+	return 0;
+}
+
+static const struct rtc_class_ops em3027_rtc_ops = {
+	.read_time = em3027_get_time,
+	.set_time = em3027_set_time,
+};
+
+static int em3027_probe(struct i2c_client *client)
+{
+	struct rtc_device *rtc;
+
+	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
+		return -ENODEV;
+
+	rtc = devm_rtc_device_register(&client->dev, em3027_driver.driver.name,
+				  &em3027_rtc_ops, THIS_MODULE);
+	if (IS_ERR(rtc))
+		return PTR_ERR(rtc);
+
+	i2c_set_clientdata(client, rtc);
+
+	return 0;
+}
+
+static const struct i2c_device_id em3027_id[] = {
+	{ .name = "em3027" },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, em3027_id);
+
+#ifdef CONFIG_OF
+static const struct of_device_id em3027_of_match[] = {
+	{ .compatible = "emmicro,em3027", },
+	{}
+};
+MODULE_DEVICE_TABLE(of, em3027_of_match);
+#endif
+
+static struct i2c_driver em3027_driver = {
+	.driver = {
+		   .name = "rtc-em3027",
+		   .of_match_table = of_match_ptr(em3027_of_match),
+	},
+	.probe = em3027_probe,
+	.id_table = em3027_id,
+};
+
+module_i2c_driver(em3027_driver);
+
+MODULE_AUTHOR("Mike Rapoport <mike@compulab.co.il>");
+MODULE_DESCRIPTION("EM Microelectronic EM3027 RTC driver");
+MODULE_LICENSE("GPL");