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, 154 insertions, 0 deletions

diff --git a/drivers/edac/debugfs.c b/drivers/edac/debugfs.c
new file mode 100644
index 000000000..8195fc9c9
--- /dev/null
+++ b/drivers/edac/debugfs.c
@@ -0,0 +1,154 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+#include <linux/string_choices.h>
+
+#include "edac_module.h"
+
+static struct dentry *edac_debugfs;
+
+static ssize_t edac_fake_inject_write(struct file *file,
+				      const char __user *data,
+				      size_t count, loff_t *ppos)
+{
+	struct device *dev = file->private_data;
+	struct mem_ctl_info *mci = to_mci(dev);
+	static enum hw_event_mc_err_type type;
+	u16 errcount = mci->fake_inject_count;
+
+	if (!errcount)
+		errcount = 1;
+
+	type = mci->fake_inject_ue ? HW_EVENT_ERR_UNCORRECTED
+				   : HW_EVENT_ERR_CORRECTED;
+
+	printk(KERN_DEBUG
+	       "Generating %d %s fake error%s to %d.%d.%d to test core handling. NOTE: this won't test the driver-specific decoding logic.\n",
+		errcount,
+		(type == HW_EVENT_ERR_UNCORRECTED) ? "UE" : "CE",
+		str_plural(errcount),
+		mci->fake_inject_layer[0],
+		mci->fake_inject_layer[1],
+		mci->fake_inject_layer[2]
+	       );
+	edac_mc_handle_error(type, mci, errcount, 0, 0, 0,
+			     mci->fake_inject_layer[0],
+			     mci->fake_inject_layer[1],
+			     mci->fake_inject_layer[2],
+			     "FAKE ERROR", "for EDAC testing only");
+
+	return count;
+}
+
+static const struct file_operations debug_fake_inject_fops = {
+	.open = simple_open,
+	.write = edac_fake_inject_write,
+	.llseek = generic_file_llseek,
+};
+
+void __init edac_debugfs_init(void)
+{
+	edac_debugfs = debugfs_create_dir("edac", NULL);
+}
+
+void edac_debugfs_exit(void)
+{
+	debugfs_remove_recursive(edac_debugfs);
+}
+
+void edac_create_debugfs_nodes(struct mem_ctl_info *mci)
+{
+	struct dentry *parent;
+	char name[80];
+	int i;
+
+	parent = debugfs_create_dir(mci->dev.kobj.name, edac_debugfs);
+
+	for (i = 0; i < mci->n_layers; i++) {
+		sprintf(name, "fake_inject_%s",
+			     edac_layer_name[mci->layers[i].type]);
+		debugfs_create_u8(name, S_IRUGO | S_IWUSR, parent,
+				  &mci->fake_inject_layer[i]);
+	}
+
+	debugfs_create_bool("fake_inject_ue", S_IRUGO | S_IWUSR, parent,
+			    &mci->fake_inject_ue);
+
+	debugfs_create_u16("fake_inject_count", S_IRUGO | S_IWUSR, parent,
+			   &mci->fake_inject_count);
+
+	debugfs_create_file("fake_inject", S_IWUSR, parent, &mci->dev,
+			    &debug_fake_inject_fops);
+
+	mci->debugfs = parent;
+}
+
+/* Create a toplevel dir under EDAC's debugfs hierarchy */
+struct dentry *edac_debugfs_create_dir(const char *dirname)
+{
+	if (!edac_debugfs)
+		return NULL;
+
+	return debugfs_create_dir(dirname, edac_debugfs);
+}
+EXPORT_SYMBOL_GPL(edac_debugfs_create_dir);
+
+/* Create a toplevel dir under EDAC's debugfs hierarchy with parent @parent */
+struct dentry *
+edac_debugfs_create_dir_at(const char *dirname, struct dentry *parent)
+{
+	return debugfs_create_dir(dirname, parent);
+}
+EXPORT_SYMBOL_GPL(edac_debugfs_create_dir_at);
+
+/*
+ * Create a file under EDAC's hierarchy or a sub-hierarchy:
+ *
+ * @name: file name
+ * @mode: file permissions
+ * @parent: parent dentry. If NULL, it becomes the toplevel EDAC dir
+ * @data: private data of caller
+ * @fops: file operations of this file
+ */
+struct dentry *
+edac_debugfs_create_file(const char *name, umode_t mode, struct dentry *parent,
+			 void *data, const struct file_operations *fops)
+{
+	if (!parent)
+		parent = edac_debugfs;
+
+	return debugfs_create_file(name, mode, parent, data, fops);
+}
+EXPORT_SYMBOL_GPL(edac_debugfs_create_file);
+
+/* Wrapper for debugfs_create_x8() */
+void edac_debugfs_create_x8(const char *name, umode_t mode,
+			    struct dentry *parent, u8 *value)
+{
+	if (!parent)
+		parent = edac_debugfs;
+
+	debugfs_create_x8(name, mode, parent, value);
+}
+EXPORT_SYMBOL_GPL(edac_debugfs_create_x8);
+
+/* Wrapper for debugfs_create_x16() */
+void edac_debugfs_create_x16(const char *name, umode_t mode,
+			     struct dentry *parent, u16 *value)
+{
+	if (!parent)
+		parent = edac_debugfs;
+
+	debugfs_create_x16(name, mode, parent, value);
+}
+EXPORT_SYMBOL_GPL(edac_debugfs_create_x16);
+
+/* Wrapper for debugfs_create_x32() */
+void edac_debugfs_create_x32(const char *name, umode_t mode,
+			     struct dentry *parent, u32 *value)
+{
+	if (!parent)
+		parent = edac_debugfs;
+
+	debugfs_create_x32(name, mode, parent, value);
+}
+EXPORT_SYMBOL_GPL(edac_debugfs_create_x32);