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, 43 insertions, 0 deletions

diff --git a/drivers/char/Makefile b/drivers/char/Makefile
new file mode 100644
index 000000000..a46d7bf7c
--- /dev/null
+++ b/drivers/char/Makefile
@@ -0,0 +1,43 @@
+# SPDX-License-Identifier: GPL-2.0
+#
+# Makefile for the kernel character device drivers.
+#
+
+obj-y				+= mem.o random.o
+obj-$(CONFIG_TTY_PRINTK)	+= ttyprintk.o
+obj-y				+= misc.o
+obj-$(CONFIG_TEST_MISC_MINOR)	+= misc_minor_kunit.o
+obj-$(CONFIG_ATARI_DSP56K)	+= dsp56k.o
+obj-$(CONFIG_VIRTIO_CONSOLE)	+= virtio_console.o
+obj-$(CONFIG_UV_MMTIMER)	+= uv_mmtimer.o
+obj-$(CONFIG_IBM_BSR)		+= bsr.o
+
+obj-$(CONFIG_PRINTER)		+= lp.o
+
+obj-$(CONFIG_APM_EMULATION)	+= apm-emulation.o
+
+obj-$(CONFIG_SONYPI)		+= sonypi.o
+obj-$(CONFIG_HPET)		+= hpet.o
+obj-$(CONFIG_XILINX_HWICAP)	+= xilinx_hwicap/
+obj-$(CONFIG_NVRAM)		+= nvram.o
+obj-$(CONFIG_TOSHIBA)		+= toshiba.o
+obj-$(CONFIG_DS1620)		+= ds1620.o
+obj-$(CONFIG_HW_RANDOM)		+= hw_random/
+obj-$(CONFIG_PPDEV)		+= ppdev.o
+obj-$(CONFIG_NWBUTTON)		+= nwbutton.o
+obj-$(CONFIG_NWFLASH)		+= nwflash.o
+obj-$(CONFIG_SCx200_GPIO)	+= scx200_gpio.o
+obj-$(CONFIG_PC8736x_GPIO)	+= pc8736x_gpio.o
+obj-$(CONFIG_NSC_GPIO)		+= nsc_gpio.o
+obj-$(CONFIG_TELCLOCK)		+= tlclk.o
+
+obj-y				+= agp/
+
+obj-$(CONFIG_HANGCHECK_TIMER)	+= hangcheck-timer.o
+obj-$(CONFIG_TCG_TPM)		+= tpm/
+
+obj-$(CONFIG_PS3_FLASH)		+= ps3flash.o
+
+obj-$(CONFIG_XILLYBUS_CLASS)	+= xillybus/
+obj-$(CONFIG_POWERNV_OP_PANEL)	+= powernv-op-panel.o
+obj-$(CONFIG_ADI)		+= adi.o