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, 38 insertions, 0 deletions

diff --git a/drivers/scsi/scsi_sysctl.c b/drivers/scsi/scsi_sysctl.c
new file mode 100644
index 000000000..055a03a83
--- /dev/null
+++ b/drivers/scsi/scsi_sysctl.c
@@ -0,0 +1,38 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2003 Christoph Hellwig.
+ */
+
+#include <linux/errno.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/sysctl.h>
+
+#include "scsi_logging.h"
+#include "scsi_priv.h"
+
+
+static const struct ctl_table scsi_table[] = {
+	{ .procname	= "logging_level",
+	  .data		= &scsi_logging_level,
+	  .maxlen	= sizeof(scsi_logging_level),
+	  .mode		= 0644,
+	  .proc_handler	= proc_dointvec_minmax,
+	  .extra1	= SYSCTL_ZERO,
+	  .extra2	= SYSCTL_INT_MAX },
+};
+
+static struct ctl_table_header *scsi_table_header;
+
+int __init scsi_init_sysctl(void)
+{
+	scsi_table_header = register_sysctl("dev/scsi", scsi_table);
+	if (!scsi_table_header)
+		return -ENOMEM;
+	return 0;
+}
+
+void scsi_exit_sysctl(void)
+{
+	unregister_sysctl_table(scsi_table_header);
+}