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, 121 insertions, 0 deletions

diff --git a/drivers/base/regmap/regmap-mdio.c b/drivers/base/regmap/regmap-mdio.c
new file mode 100644
index 000000000..9573bf3b5
--- /dev/null
+++ b/drivers/base/regmap/regmap-mdio.c
@@ -0,0 +1,121 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/errno.h>
+#include <linux/mdio.h>
+#include <linux/module.h>
+#include <linux/regmap.h>
+
+#define REGVAL_MASK		GENMASK(15, 0)
+#define REGNUM_C22_MASK		GENMASK(4, 0)
+/* Clause-45 mask includes the device type (5 bit) and actual register number (16 bit) */
+#define REGNUM_C45_MASK		GENMASK(20, 0)
+
+static int regmap_mdio_c22_read(void *context, unsigned int reg, unsigned int *val)
+{
+	struct mdio_device *mdio_dev = context;
+	int ret;
+
+	if (unlikely(reg & ~REGNUM_C22_MASK))
+		return -ENXIO;
+
+	ret = mdiodev_read(mdio_dev, reg);
+	if (ret < 0)
+		return ret;
+
+	*val = ret & REGVAL_MASK;
+
+	return 0;
+}
+
+static int regmap_mdio_c22_write(void *context, unsigned int reg, unsigned int val)
+{
+	struct mdio_device *mdio_dev = context;
+
+	if (unlikely(reg & ~REGNUM_C22_MASK))
+		return -ENXIO;
+
+	return mdiodev_write(mdio_dev, reg, val);
+}
+
+static const struct regmap_bus regmap_mdio_c22_bus = {
+	.reg_write = regmap_mdio_c22_write,
+	.reg_read = regmap_mdio_c22_read,
+};
+
+static int regmap_mdio_c45_read(void *context, unsigned int reg, unsigned int *val)
+{
+	struct mdio_device *mdio_dev = context;
+	unsigned int devad;
+	int ret;
+
+	if (unlikely(reg & ~REGNUM_C45_MASK))
+		return -ENXIO;
+
+	devad = reg >> REGMAP_MDIO_C45_DEVAD_SHIFT;
+	reg = reg & REGMAP_MDIO_C45_REGNUM_MASK;
+
+	ret = mdiodev_c45_read(mdio_dev, devad, reg);
+	if (ret < 0)
+		return ret;
+
+	*val = ret & REGVAL_MASK;
+
+	return 0;
+}
+
+static int regmap_mdio_c45_write(void *context, unsigned int reg, unsigned int val)
+{
+	struct mdio_device *mdio_dev = context;
+	unsigned int devad;
+
+	if (unlikely(reg & ~REGNUM_C45_MASK))
+		return -ENXIO;
+
+	devad = reg >> REGMAP_MDIO_C45_DEVAD_SHIFT;
+	reg = reg & REGMAP_MDIO_C45_REGNUM_MASK;
+
+	return mdiodev_c45_write(mdio_dev, devad, reg, val);
+}
+
+static const struct regmap_bus regmap_mdio_c45_bus = {
+	.reg_write = regmap_mdio_c45_write,
+	.reg_read = regmap_mdio_c45_read,
+};
+
+struct regmap *__regmap_init_mdio(struct mdio_device *mdio_dev,
+	const struct regmap_config *config, struct lock_class_key *lock_key,
+	const char *lock_name)
+{
+	const struct regmap_bus *bus;
+
+	if (config->reg_bits == 5 && config->val_bits == 16)
+		bus = &regmap_mdio_c22_bus;
+	else if (config->reg_bits == 21 && config->val_bits == 16)
+		bus = &regmap_mdio_c45_bus;
+	else
+		return ERR_PTR(-EOPNOTSUPP);
+
+	return __regmap_init(&mdio_dev->dev, bus, mdio_dev, config, lock_key, lock_name);
+}
+EXPORT_SYMBOL_GPL(__regmap_init_mdio);
+
+struct regmap *__devm_regmap_init_mdio(struct mdio_device *mdio_dev,
+	const struct regmap_config *config, struct lock_class_key *lock_key,
+	const char *lock_name)
+{
+	const struct regmap_bus *bus;
+
+	if (config->reg_bits == 5 && config->val_bits == 16)
+		bus = &regmap_mdio_c22_bus;
+	else if (config->reg_bits == 21 && config->val_bits == 16)
+		bus = &regmap_mdio_c45_bus;
+	else
+		return ERR_PTR(-EOPNOTSUPP);
+
+	return __devm_regmap_init(&mdio_dev->dev, bus, mdio_dev, config, lock_key, lock_name);
+}
+EXPORT_SYMBOL_GPL(__devm_regmap_init_mdio);
+
+MODULE_AUTHOR("Sander Vanheule <sander@svanheule.net>");
+MODULE_DESCRIPTION("regmap MDIO Module");
+MODULE_LICENSE("GPL v2");