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, 79 insertions, 0 deletions

diff --git a/drivers/scsi/arm/msgqueue.h b/drivers/scsi/arm/msgqueue.h
new file mode 100644
index 000000000..4bcc400f5
--- /dev/null
+++ b/drivers/scsi/arm/msgqueue.h
@@ -0,0 +1,79 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ *  linux/drivers/acorn/scsi/msgqueue.h
+ *
+ *  Copyright (C) 1997 Russell King
+ *
+ *  message queue handling
+ */
+#ifndef MSGQUEUE_H
+#define MSGQUEUE_H
+
+struct message {
+    char msg[8];
+    int length;
+    int fifo;
+};
+
+struct msgqueue_entry {
+    struct message msg;
+    struct msgqueue_entry *next;
+};
+
+#define NR_MESSAGES 4
+
+typedef struct {
+    struct msgqueue_entry *qe;
+    struct msgqueue_entry *free;
+    struct msgqueue_entry entries[NR_MESSAGES];
+} MsgQueue_t;
+
+/*
+ * Function: void msgqueue_initialise(MsgQueue_t *msgq)
+ * Purpose : initialise a message queue
+ * Params  : msgq - queue to initialise
+ */
+extern void msgqueue_initialise(MsgQueue_t *msgq);
+
+/*
+ * Function: void msgqueue_free(MsgQueue_t *msgq)
+ * Purpose : free a queue
+ * Params  : msgq - queue to free
+ */
+extern void msgqueue_free(MsgQueue_t *msgq);
+
+/*
+ * Function: int msgqueue_msglength(MsgQueue_t *msgq)
+ * Purpose : calculate the total length of all messages on the message queue
+ * Params  : msgq - queue to examine
+ * Returns : number of bytes of messages in queue
+ */
+extern int msgqueue_msglength(MsgQueue_t *msgq);
+
+/*
+ * Function: struct message *msgqueue_getmsg(MsgQueue_t *msgq, int msgno)
+ * Purpose : return a message & its length
+ * Params  : msgq   - queue to obtain message from
+ *         : msgno  - message number
+ * Returns : pointer to message string, or NULL
+ */
+extern struct message *msgqueue_getmsg(MsgQueue_t *msgq, int msgno);
+
+/*
+ * Function: int msgqueue_addmsg(MsgQueue_t *msgq, int length, ...)
+ * Purpose : add a message onto a message queue
+ * Params  : msgq   - queue to add message on
+ *	     length - length of message
+ *	     ...    - message bytes
+ * Returns : != 0 if successful
+ */
+extern int msgqueue_addmsg(MsgQueue_t *msgq, int length, ...);
+
+/*
+ * Function: void msgqueue_flush(MsgQueue_t *msgq)
+ * Purpose : flush all messages from message queue
+ * Params  : msgq - queue to flush
+ */
+extern void msgqueue_flush(MsgQueue_t *msgq);
+
+#endif