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, 133 insertions, 0 deletions

diff --git a/include/asm-generic/atomic.h b/include/asm-generic/atomic.h
new file mode 100644
index 000000000..22142c71d
--- /dev/null
+++ b/include/asm-generic/atomic.h
@@ -0,0 +1,133 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * Generic C implementation of atomic counter operations. Do not include in
+ * machine independent code.
+ *
+ * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ */
+#ifndef __ASM_GENERIC_ATOMIC_H
+#define __ASM_GENERIC_ATOMIC_H
+
+#include <asm/cmpxchg.h>
+#include <asm/barrier.h>
+
+#ifdef CONFIG_SMP
+
+/* we can build all atomic primitives from cmpxchg */
+
+#define ATOMIC_OP(op, c_op)						\
+static inline void generic_atomic_##op(int i, atomic_t *v)		\
+{									\
+	int c, old;							\
+									\
+	c = v->counter;							\
+	while ((old = arch_cmpxchg(&v->counter, c, c c_op i)) != c)	\
+		c = old;						\
+}
+
+#define ATOMIC_OP_RETURN(op, c_op)					\
+static inline int generic_atomic_##op##_return(int i, atomic_t *v)	\
+{									\
+	int c, old;							\
+									\
+	c = v->counter;							\
+	while ((old = arch_cmpxchg(&v->counter, c, c c_op i)) != c)	\
+		c = old;						\
+									\
+	return c c_op i;						\
+}
+
+#define ATOMIC_FETCH_OP(op, c_op)					\
+static inline int generic_atomic_fetch_##op(int i, atomic_t *v)		\
+{									\
+	int c, old;							\
+									\
+	c = v->counter;							\
+	while ((old = arch_cmpxchg(&v->counter, c, c c_op i)) != c)	\
+		c = old;						\
+									\
+	return c;							\
+}
+
+#else
+
+#include <linux/irqflags.h>
+
+#define ATOMIC_OP(op, c_op)						\
+static inline void generic_atomic_##op(int i, atomic_t *v)		\
+{									\
+	unsigned long flags;						\
+									\
+	raw_local_irq_save(flags);					\
+	v->counter = v->counter c_op i;					\
+	raw_local_irq_restore(flags);					\
+}
+
+#define ATOMIC_OP_RETURN(op, c_op)					\
+static inline int generic_atomic_##op##_return(int i, atomic_t *v)	\
+{									\
+	unsigned long flags;						\
+	int ret;							\
+									\
+	raw_local_irq_save(flags);					\
+	ret = (v->counter = v->counter c_op i);				\
+	raw_local_irq_restore(flags);					\
+									\
+	return ret;							\
+}
+
+#define ATOMIC_FETCH_OP(op, c_op)					\
+static inline int generic_atomic_fetch_##op(int i, atomic_t *v)		\
+{									\
+	unsigned long flags;						\
+	int ret;							\
+									\
+	raw_local_irq_save(flags);					\
+	ret = v->counter;						\
+	v->counter = v->counter c_op i;					\
+	raw_local_irq_restore(flags);					\
+									\
+	return ret;							\
+}
+
+#endif /* CONFIG_SMP */
+
+ATOMIC_OP_RETURN(add, +)
+ATOMIC_OP_RETURN(sub, -)
+
+ATOMIC_FETCH_OP(add, +)
+ATOMIC_FETCH_OP(sub, -)
+ATOMIC_FETCH_OP(and, &)
+ATOMIC_FETCH_OP(or, |)
+ATOMIC_FETCH_OP(xor, ^)
+
+ATOMIC_OP(add, +)
+ATOMIC_OP(sub, -)
+ATOMIC_OP(and, &)
+ATOMIC_OP(or, |)
+ATOMIC_OP(xor, ^)
+
+#undef ATOMIC_FETCH_OP
+#undef ATOMIC_OP_RETURN
+#undef ATOMIC_OP
+
+#define arch_atomic_add_return			generic_atomic_add_return
+#define arch_atomic_sub_return			generic_atomic_sub_return
+
+#define arch_atomic_fetch_add			generic_atomic_fetch_add
+#define arch_atomic_fetch_sub			generic_atomic_fetch_sub
+#define arch_atomic_fetch_and			generic_atomic_fetch_and
+#define arch_atomic_fetch_or			generic_atomic_fetch_or
+#define arch_atomic_fetch_xor			generic_atomic_fetch_xor
+
+#define arch_atomic_add				generic_atomic_add
+#define arch_atomic_sub				generic_atomic_sub
+#define arch_atomic_and				generic_atomic_and
+#define arch_atomic_or				generic_atomic_or
+#define arch_atomic_xor				generic_atomic_xor
+
+#define arch_atomic_read(v)			READ_ONCE((v)->counter)
+#define arch_atomic_set(v, i)			WRITE_ONCE(((v)->counter), (i))
+
+#endif /* __ASM_GENERIC_ATOMIC_H */