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, 40 insertions, 0 deletions

diff --git a/drivers/input/vivaldi-fmap.c b/drivers/input/vivaldi-fmap.c
new file mode 100644
index 000000000..978949eba
--- /dev/null
+++ b/drivers/input/vivaldi-fmap.c
@@ -0,0 +1,40 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Helpers for ChromeOS Vivaldi keyboard function row mapping
+ *
+ * Copyright (C) 2022 Google, Inc
+ */
+
+#include <linux/export.h>
+#include <linux/input/vivaldi-fmap.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/types.h>
+
+/**
+ * vivaldi_function_row_physmap_show - Print vivaldi function row physmap attribute
+ * @data: The vivaldi function row map
+ * @buf: Buffer to print the function row phsymap to
+ */
+ssize_t vivaldi_function_row_physmap_show(const struct vivaldi_data *data,
+					  char *buf)
+{
+	ssize_t size = 0;
+	int i;
+	const u32 *physmap = data->function_row_physmap;
+
+	if (!data->num_function_row_keys)
+		return 0;
+
+	for (i = 0; i < data->num_function_row_keys; i++)
+		size += sysfs_emit_at(buf, size,
+				      "%s%02X", size ? " " : "", physmap[i]);
+	if (size)
+		size += sysfs_emit_at(buf, size, "\n");
+
+	return size;
+}
+EXPORT_SYMBOL_GPL(vivaldi_function_row_physmap_show);
+
+MODULE_DESCRIPTION("Helpers for ChromeOS Vivaldi keyboard function row mapping");
+MODULE_LICENSE("GPL");