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, 87 insertions, 0 deletions

diff --git a/rust/helpers/atomic_ext.c b/rust/helpers/atomic_ext.c
new file mode 100644
index 000000000..c267d5190
--- /dev/null
+++ b/rust/helpers/atomic_ext.c
@@ -0,0 +1,87 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <asm/barrier.h>
+#include <asm/rwonce.h>
+#include <linux/atomic.h>
+
+#define GEN_READ_HELPER(tname, type)						\
+__rust_helper type rust_helper_atomic_##tname##_read(type *ptr)			\
+{										\
+	return READ_ONCE(*ptr);							\
+}
+
+#define GEN_SET_HELPER(tname, type)						\
+__rust_helper void rust_helper_atomic_##tname##_set(type *ptr, type val)	\
+{										\
+	WRITE_ONCE(*ptr, val);							\
+}
+
+#define GEN_READ_ACQUIRE_HELPER(tname, type)					\
+__rust_helper type rust_helper_atomic_##tname##_read_acquire(type *ptr)		\
+{										\
+	return smp_load_acquire(ptr);						\
+}
+
+#define GEN_SET_RELEASE_HELPER(tname, type)					\
+__rust_helper void rust_helper_atomic_##tname##_set_release(type *ptr, type val)\
+{										\
+	smp_store_release(ptr, val);						\
+}
+
+#define GEN_READ_SET_HELPERS(tname, type)					\
+	GEN_READ_HELPER(tname, type)						\
+	GEN_SET_HELPER(tname, type)						\
+	GEN_READ_ACQUIRE_HELPER(tname, type)					\
+	GEN_SET_RELEASE_HELPER(tname, type)					\
+
+GEN_READ_SET_HELPERS(i8, s8)
+GEN_READ_SET_HELPERS(i16, s16)
+GEN_READ_SET_HELPERS(ptr, const void *)
+
+/*
+ * xchg helpers depend on ARCH_SUPPORTS_ATOMIC_RMW and on the
+ * architecture provding xchg() support for i8 and i16.
+ *
+ * The architectures that currently support Rust (x86_64, armv7,
+ * arm64, riscv, and loongarch) satisfy these requirements.
+ */
+#define GEN_XCHG_HELPER(tname, type, suffix)					\
+__rust_helper type								\
+rust_helper_atomic_##tname##_xchg##suffix(type *ptr, type new)			\
+{										\
+	return xchg##suffix(ptr, new);					\
+}
+
+#define GEN_XCHG_HELPERS(tname, type)						\
+	GEN_XCHG_HELPER(tname, type, )						\
+	GEN_XCHG_HELPER(tname, type, _acquire)					\
+	GEN_XCHG_HELPER(tname, type, _release)					\
+	GEN_XCHG_HELPER(tname, type, _relaxed)					\
+
+GEN_XCHG_HELPERS(i8, s8)
+GEN_XCHG_HELPERS(i16, s16)
+GEN_XCHG_HELPERS(ptr, const void *)
+
+/*
+ * try_cmpxchg helpers depend on ARCH_SUPPORTS_ATOMIC_RMW and on the
+ * architecture provding try_cmpxchg() support for i8 and i16.
+ *
+ * The architectures that currently support Rust (x86_64, armv7,
+ * arm64, riscv, and loongarch) satisfy these requirements.
+ */
+#define GEN_TRY_CMPXCHG_HELPER(tname, type, suffix)				\
+__rust_helper bool								\
+rust_helper_atomic_##tname##_try_cmpxchg##suffix(type *ptr, type *old, type new)\
+{										\
+	return try_cmpxchg##suffix(ptr, old, new);				\
+}
+
+#define GEN_TRY_CMPXCHG_HELPERS(tname, type)					\
+	GEN_TRY_CMPXCHG_HELPER(tname, type, )					\
+	GEN_TRY_CMPXCHG_HELPER(tname, type, _acquire)				\
+	GEN_TRY_CMPXCHG_HELPER(tname, type, _release)				\
+	GEN_TRY_CMPXCHG_HELPER(tname, type, _relaxed)				\
+
+GEN_TRY_CMPXCHG_HELPERS(i8, s8)
+GEN_TRY_CMPXCHG_HELPERS(i16, s16)
+GEN_TRY_CMPXCHG_HELPERS(ptr, const void *)