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, 60 insertions, 0 deletions

diff --git a/lib/muldi3.c b/lib/muldi3.c
new file mode 100644
index 000000000..9150ac130
--- /dev/null
+++ b/lib/muldi3.c
@@ -0,0 +1,60 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ */
+
+#include <linux/export.h>
+#include <linux/libgcc.h>
+
+#define W_TYPE_SIZE 32
+
+#define __ll_B ((unsigned long) 1 << (W_TYPE_SIZE / 2))
+#define __ll_lowpart(t) ((unsigned long) (t) & (__ll_B - 1))
+#define __ll_highpart(t) ((unsigned long) (t) >> (W_TYPE_SIZE / 2))
+
+/* If we still don't have umul_ppmm, define it using plain C.  */
+#if !defined(umul_ppmm)
+#define umul_ppmm(w1, w0, u, v)						\
+	do {								\
+		unsigned long __x0, __x1, __x2, __x3;			\
+		unsigned short __ul, __vl, __uh, __vh;			\
+									\
+		__ul = __ll_lowpart(u);					\
+		__uh = __ll_highpart(u);				\
+		__vl = __ll_lowpart(v);					\
+		__vh = __ll_highpart(v);				\
+									\
+		__x0 = (unsigned long) __ul * __vl;			\
+		__x1 = (unsigned long) __ul * __vh;			\
+		__x2 = (unsigned long) __uh * __vl;			\
+		__x3 = (unsigned long) __uh * __vh;			\
+									\
+		__x1 += __ll_highpart(__x0); /* this can't give carry */\
+		__x1 += __x2; /* but this indeed can */			\
+		if (__x1 < __x2) /* did we get it? */			\
+		__x3 += __ll_B; /* yes, add it in the proper pos */	\
+									\
+		(w1) = __x3 + __ll_highpart(__x1);			\
+		(w0) = __ll_lowpart(__x1) * __ll_B + __ll_lowpart(__x0);\
+	} while (0)
+#endif
+
+#if !defined(__umulsidi3)
+#define __umulsidi3(u, v) ({				\
+	DWunion __w;					\
+	umul_ppmm(__w.s.high, __w.s.low, u, v);		\
+	__w.ll;						\
+	})
+#endif
+
+long long notrace __muldi3(long long u, long long v)
+{
+	const DWunion uu = {.ll = u};
+	const DWunion vv = {.ll = v};
+	DWunion w = {.ll = __umulsidi3(uu.s.low, vv.s.low)};
+
+	w.s.high += ((unsigned long) uu.s.low * (unsigned long) vv.s.high
+		+ (unsigned long) uu.s.high * (unsigned long) vv.s.low);
+
+	return w.ll;
+}
+EXPORT_SYMBOL(__muldi3);