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, 52 insertions, 0 deletions

diff --git a/Documentation/driver-api/target.rst b/Documentation/driver-api/target.rst
new file mode 100644
index 000000000..c70ca2517
--- /dev/null
+++ b/Documentation/driver-api/target.rst
@@ -0,0 +1,52 @@
+=================================
+target and iSCSI Interfaces Guide
+=================================
+
+Introduction and Overview
+=========================
+
+TBD
+
+Target core device interfaces
+=============================
+
+This section is blank because no kerneldoc comments have been added to
+drivers/target/target_core_device.c.
+
+Target core transport interfaces
+================================
+
+.. kernel-doc:: drivers/target/target_core_transport.c
+    :export:
+
+Target-supported userspace I/O
+==============================
+
+.. kernel-doc:: drivers/target/target_core_user.c
+    :doc: Userspace I/O
+
+.. kernel-doc:: include/uapi/linux/target_core_user.h
+    :doc: Ring Design
+
+iSCSI helper functions
+======================
+
+.. kernel-doc:: drivers/scsi/libiscsi.c
+   :export:
+
+
+iSCSI boot information
+======================
+
+.. kernel-doc:: drivers/scsi/iscsi_boot_sysfs.c
+   :export:
+
+iSCSI TCP interfaces
+====================
+
+.. kernel-doc:: drivers/scsi/iscsi_tcp.c
+   :internal:
+
+.. kernel-doc:: drivers/scsi/libiscsi_tcp.c
+   :export:
+