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, 50 insertions, 0 deletions

diff --git a/Documentation/driver-api/firewire.rst b/Documentation/driver-api/firewire.rst
new file mode 100644
index 000000000..28a32410f
--- /dev/null
+++ b/Documentation/driver-api/firewire.rst
@@ -0,0 +1,50 @@
+===========================================
+Firewire (IEEE 1394) driver Interface Guide
+===========================================
+
+Introduction and Overview
+=========================
+
+The Linux FireWire subsystem adds some interfaces into the Linux system to
+ use/maintain+any resource on IEEE 1394 bus.
+
+The main purpose of these interfaces is to access address space on each node
+on IEEE 1394 bus by ISO/IEC 13213 (IEEE 1212) procedure, and to control
+isochronous resources on the bus by IEEE 1394 procedure.
+
+Two types of interfaces are added, according to consumers of the interface. A
+set of userspace interfaces is available via `firewire character devices`. A set
+of kernel interfaces is available via exported symbols in `firewire-core` module.
+
+Firewire char device data structures
+====================================
+
+.. include:: ../ABI/stable/firewire-cdev
+    :literal:
+
+.. kernel-doc:: include/uapi/linux/firewire-cdev.h
+    :internal:
+
+Firewire device probing and sysfs interfaces
+============================================
+
+.. include:: ../ABI/stable/sysfs-bus-firewire
+    :literal:
+
+.. kernel-doc:: drivers/firewire/core-device.c
+    :export:
+
+Firewire core transaction interfaces
+====================================
+
+.. kernel-doc:: drivers/firewire/core-transaction.c
+    :export:
+
+Firewire Isochronous I/O interfaces
+===================================
+
+.. kernel-doc:: include/linux/firewire.h
+   :functions: fw_iso_context_schedule_flush_completions
+.. kernel-doc:: drivers/firewire/core-iso.c
+   :export:
+