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, 49 insertions, 0 deletions

diff --git a/arch/m68k/coldfire/cache.c b/arch/m68k/coldfire/cache.c
new file mode 100644
index 000000000..98ee89b87
--- /dev/null
+++ b/arch/m68k/coldfire/cache.c
@@ -0,0 +1,49 @@
+// SPDX-License-Identifier: GPL-2.0
+/***************************************************************************/
+
+/*
+ *	cache.c -- general ColdFire Cache maintenance code
+ *
+ *	Copyright (C) 2010, Greg Ungerer (gerg@snapgear.com)
+ */
+
+/***************************************************************************/
+
+#include <linux/kernel.h>
+#include <asm/coldfire.h>
+#include <asm/mcfsim.h>
+
+/***************************************************************************/
+#ifdef CACHE_PUSH
+/***************************************************************************/
+
+/*
+ *	Use cpushl to push all dirty cache lines back to memory.
+ *	Older versions of GAS don't seem to know how to generate the
+ *	ColdFire cpushl instruction... Oh well, bit stuff it for now.
+ */
+
+void mcf_cache_push(void)
+{
+	__asm__ __volatile__ (
+		"clrl	%%d0\n\t"
+		"1:\n\t"
+		"movel	%%d0,%%a0\n\t"
+		"2:\n\t"
+		".word	0xf468\n\t"
+		"addl	%0,%%a0\n\t"
+		"cmpl	%1,%%a0\n\t"
+		"blt	2b\n\t"
+		"addql	#1,%%d0\n\t"
+		"cmpil	%2,%%d0\n\t"
+		"bne	1b\n\t"
+		: /* No output */
+		: "i" (CACHE_LINE_SIZE),
+		  "i" (DCACHE_SIZE / CACHE_WAYS),
+		  "i" (CACHE_WAYS)
+		: "d0", "a0" );
+}
+
+/***************************************************************************/
+#endif /* CACHE_PUSH */
+/***************************************************************************/