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, 94 insertions, 0 deletions

diff --git a/drivers/fpga/xilinx-selectmap.c b/drivers/fpga/xilinx-selectmap.c
new file mode 100644
index 000000000..d0cbb5fdf
--- /dev/null
+++ b/drivers/fpga/xilinx-selectmap.c
@@ -0,0 +1,94 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Xilinx Spartan6 and 7 Series SelectMAP interface driver
+ *
+ * (C) 2024 Charles Perry <charles.perry@savoirfairelinux.com>
+ *
+ * Manage Xilinx FPGA firmware loaded over the SelectMAP configuration
+ * interface.
+ */
+
+#include "xilinx-core.h"
+
+#include <linux/gpio/consumer.h>
+#include <linux/io.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+
+struct xilinx_selectmap_conf {
+	struct xilinx_fpga_core core;
+	void __iomem *base;
+};
+
+#define to_xilinx_selectmap_conf(obj) \
+	container_of(obj, struct xilinx_selectmap_conf, core)
+
+static int xilinx_selectmap_write(struct xilinx_fpga_core *core,
+				  const char *buf, size_t count)
+{
+	struct xilinx_selectmap_conf *conf = to_xilinx_selectmap_conf(core);
+	size_t i;
+
+	for (i = 0; i < count; ++i)
+		writeb(buf[i], conf->base);
+
+	return 0;
+}
+
+static int xilinx_selectmap_probe(struct platform_device *pdev)
+{
+	struct xilinx_selectmap_conf *conf;
+	struct gpio_desc *gpio;
+	void __iomem *base;
+
+	conf = devm_kzalloc(&pdev->dev, sizeof(*conf), GFP_KERNEL);
+	if (!conf)
+		return -ENOMEM;
+
+	conf->core.dev = &pdev->dev;
+	conf->core.write = xilinx_selectmap_write;
+
+	base = devm_platform_get_and_ioremap_resource(pdev, 0, NULL);
+	if (IS_ERR(base))
+		return dev_err_probe(&pdev->dev, PTR_ERR(base),
+				     "ioremap error\n");
+	conf->base = base;
+
+	/* CSI_B is active low */
+	gpio = devm_gpiod_get_optional(&pdev->dev, "csi", GPIOD_OUT_HIGH);
+	if (IS_ERR(gpio))
+		return dev_err_probe(&pdev->dev, PTR_ERR(gpio),
+				     "Failed to get CSI_B gpio\n");
+
+	/* RDWR_B is active low */
+	gpio = devm_gpiod_get_optional(&pdev->dev, "rdwr", GPIOD_OUT_HIGH);
+	if (IS_ERR(gpio))
+		return dev_err_probe(&pdev->dev, PTR_ERR(gpio),
+				     "Failed to get RDWR_B gpio\n");
+
+	return xilinx_core_probe(&conf->core);
+}
+
+static const struct of_device_id xlnx_selectmap_of_match[] = {
+	{ .compatible = "xlnx,fpga-xc7s-selectmap", }, // Spartan-7
+	{ .compatible = "xlnx,fpga-xc7a-selectmap", }, // Artix-7
+	{ .compatible = "xlnx,fpga-xc7k-selectmap", }, // Kintex-7
+	{ .compatible = "xlnx,fpga-xc7v-selectmap", }, // Virtex-7
+	{},
+};
+MODULE_DEVICE_TABLE(of, xlnx_selectmap_of_match);
+
+static struct platform_driver xilinx_selectmap_driver = {
+	.driver = {
+		.name = "xilinx-selectmap",
+		.of_match_table = xlnx_selectmap_of_match,
+	},
+	.probe  = xilinx_selectmap_probe,
+};
+
+module_platform_driver(xilinx_selectmap_driver);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Charles Perry <charles.perry@savoirfairelinux.com>");
+MODULE_DESCRIPTION("Load Xilinx FPGA firmware over SelectMap");