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, 62 insertions, 0 deletions

diff --git a/include/uapi/fwctl/pds.h b/include/uapi/fwctl/pds.h
new file mode 100644
index 000000000..66be32411
--- /dev/null
+++ b/include/uapi/fwctl/pds.h
@@ -0,0 +1,62 @@
+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+/* Copyright(c) Advanced Micro Devices, Inc */
+
+/*
+ * fwctl interface info for pds_fwctl
+ */
+
+#ifndef _UAPI_FWCTL_PDS_H_
+#define _UAPI_FWCTL_PDS_H_
+
+#include <linux/types.h>
+
+/**
+ * struct fwctl_info_pds
+ * @uctx_caps:  bitmap of firmware capabilities
+ *
+ * Return basic information about the FW interface available.
+ */
+struct fwctl_info_pds {
+	__u32 uctx_caps;
+};
+
+/**
+ * enum pds_fwctl_capabilities
+ * @PDS_FWCTL_QUERY_CAP: firmware can be queried for information
+ * @PDS_FWCTL_SEND_CAP:  firmware can be sent commands
+ */
+enum pds_fwctl_capabilities {
+	PDS_FWCTL_QUERY_CAP = 0,
+	PDS_FWCTL_SEND_CAP,
+};
+
+/**
+ * struct fwctl_rpc_pds
+ * @in.op:       requested operation code
+ * @in.ep:       firmware endpoint to operate on
+ * @in.rsvd:     reserved
+ * @in.len:      length of payload data
+ * @in.payload:  address of payload buffer
+ * @in:          rpc in parameters
+ * @out.retval:  operation result value
+ * @out.rsvd:    reserved
+ * @out.len:     length of result data buffer
+ * @out.payload: address of payload data buffer
+ * @out:         rpc out parameters
+ */
+struct fwctl_rpc_pds {
+	struct {
+		__u32 op;
+		__u32 ep;
+		__u32 rsvd;
+		__u32 len;
+		__aligned_u64 payload;
+	} in;
+	struct {
+		__u32 retval;
+		__u32 rsvd[2];
+		__u32 len;
+		__aligned_u64 payload;
+	} out;
+};
+#endif /* _UAPI_FWCTL_PDS_H_ */