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, 43 insertions, 0 deletions

diff --git a/arch/powerpc/boot/ofconsole.c b/arch/powerpc/boot/ofconsole.c
new file mode 100644
index 000000000..8eb0f1c45
--- /dev/null
+++ b/arch/powerpc/boot/ofconsole.c
@@ -0,0 +1,43 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * OF console routines
+ *
+ * Copyright (C) Paul Mackerras 1997.
+ */
+#include <stddef.h>
+#include "types.h"
+#include "elf.h"
+#include "string.h"
+#include "stdio.h"
+#include "page.h"
+#include "ops.h"
+
+#include "of.h"
+
+static unsigned int of_stdout_handle;
+
+static int of_console_open(void)
+{
+	void *devp;
+
+	if (((devp = of_finddevice("/chosen")) != NULL)
+	    && (of_getprop(devp, "stdout", &of_stdout_handle,
+			   sizeof(of_stdout_handle))
+		== sizeof(of_stdout_handle))) {
+		of_stdout_handle = be32_to_cpu(of_stdout_handle);
+		return 0;
+	}
+
+	return -1;
+}
+
+static void of_console_write(const char *buf, int len)
+{
+	of_call_prom("write", 3, 1, of_stdout_handle, buf, len);
+}
+
+void of_console_init(void)
+{
+	console_ops.open = of_console_open;
+	console_ops.write = of_console_write;
+}