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, 57 insertions, 0 deletions

diff --git a/Documentation/ABI/testing/debugfs-vfio b/Documentation/ABI/testing/debugfs-vfio
new file mode 100644
index 000000000..ed2f29c3a
--- /dev/null
+++ b/Documentation/ABI/testing/debugfs-vfio
@@ -0,0 +1,57 @@
+What:		/sys/kernel/debug/vfio
+Date:		December 2023
+KernelVersion:	6.8
+Contact:	Longfang Liu <liulongfang@huawei.com>
+Description:	This debugfs file directory is used for debugging
+		of vfio devices, it's a common directory for all vfio devices.
+		Vfio core will create a device subdirectory under this
+		directory.
+
+What:		/sys/kernel/debug/vfio/<device>/migration
+Date:		December 2023
+KernelVersion:	6.8
+Contact:	Longfang Liu <liulongfang@huawei.com>
+Description:	This debugfs file directory is used for debugging
+		of vfio devices that support live migration.
+		The debugfs of each vfio device that supports live migration
+		could be created under this directory.
+
+What:		/sys/kernel/debug/vfio/<device>/migration/state
+Date:		December 2023
+KernelVersion:	6.8
+Contact:	Longfang Liu <liulongfang@huawei.com>
+Description:	Read the live migration status of the vfio device.
+		The contents of the state file reflects the migration state
+		relative to those defined in the vfio_device_mig_state enum
+
+What:		/sys/kernel/debug/vfio/<device>/migration/features
+Date:		Oct 2025
+KernelVersion:	6.18
+Contact:	Cédric Le Goater <clg@redhat.com>
+Description:	Read the migration features of the vfio device.
+
+What:		/sys/kernel/debug/vfio/<device>/pci
+Date:		June 2026
+KernelVersion:	7.2
+Contact:	Alex Williamson <alex.williamson@nvidia.com>
+Description:	This debugfs file directory is used for debugging
+		VFIO PCI devices.
+
+What:		/sys/kernel/debug/vfio/<device>/pci/nointxmask
+Date:		June 2026
+KernelVersion:	7.2
+Contact:	Alex Williamson <alex.williamson@nvidia.com>
+Description:	Read the nointxmask policy latched for this device.  This
+		policy governs whether the device may use PCI 2.3 style
+		INTx masking when supported, reporting a value of "N", or
+		requires APIC level INTx masking, reporting a value of "Y".
+
+What:		/sys/kernel/debug/vfio/<device>/pci/disable_idle_d3
+Date:		June 2026
+KernelVersion:	7.2
+Contact:	Alex Williamson <alex.williamson@nvidia.com>
+Description:	Read the disable_idle_d3 policy latched for this device.  This
+		policy governs whether the device PM runtime usage count is
+		kept elevated while the device is bound to the driver and
+		unused, reporting a value of "Y", or decremented to allow the
+		device to enter a low power state, reporting a value of "N".