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, 67 insertions, 0 deletions

diff --git a/drivers/char/tpm/tpm-dev.c b/drivers/char/tpm/tpm-dev.c
new file mode 100644
index 000000000..74488f0a7
--- /dev/null
+++ b/drivers/char/tpm/tpm-dev.c
@@ -0,0 +1,67 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2004 IBM Corporation
+ * Authors:
+ * Leendert van Doorn <leendert@watson.ibm.com>
+ * Dave Safford <safford@watson.ibm.com>
+ * Reiner Sailer <sailer@watson.ibm.com>
+ * Kylene Hall <kjhall@us.ibm.com>
+ *
+ * Copyright (C) 2013 Obsidian Research Corp
+ * Jason Gunthorpe <jgunthorpe@obsidianresearch.com>
+ *
+ * Device file system interface to the TPM
+ */
+#include <linux/slab.h>
+#include "tpm-dev.h"
+
+static int tpm_open(struct inode *inode, struct file *file)
+{
+	struct tpm_chip *chip;
+	struct file_priv *priv;
+
+	chip = container_of(inode->i_cdev, struct tpm_chip, cdev);
+
+	/* It's assured that the chip will be opened just once,
+	 * by the check of is_open variable, which is protected
+	 * by driver_lock. */
+	if (test_and_set_bit(0, &chip->is_open)) {
+		dev_dbg(&chip->dev, "Another process owns this TPM\n");
+		return -EBUSY;
+	}
+
+	priv = kzalloc_obj(*priv);
+	if (priv == NULL)
+		goto out;
+
+	tpm_common_open(file, chip, priv, NULL);
+
+	return nonseekable_open(inode, file);
+
+ out:
+	clear_bit(0, &chip->is_open);
+	return -ENOMEM;
+}
+
+/*
+ * Called on file close
+ */
+static int tpm_release(struct inode *inode, struct file *file)
+{
+	struct file_priv *priv = file->private_data;
+
+	tpm_common_release(file, priv);
+	clear_bit(0, &priv->chip->is_open);
+	kfree(priv);
+
+	return 0;
+}
+
+const struct file_operations tpm_fops = {
+	.owner = THIS_MODULE,
+	.open = tpm_open,
+	.read = tpm_common_read,
+	.write = tpm_common_write,
+	.poll = tpm_common_poll,
+	.release = tpm_release,
+};