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/include/asm-generic/error-injection.h b/include/asm-generic/error-injection.h
new file mode 100644
index 000000000..b05253f68
--- /dev/null
+++ b/include/asm-generic/error-injection.h
@@ -0,0 +1,43 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ASM_GENERIC_ERROR_INJECTION_H
+#define _ASM_GENERIC_ERROR_INJECTION_H
+
+#if defined(__KERNEL__) && !defined(__ASSEMBLY__)
+enum {
+	EI_ETYPE_NULL,		/* Return NULL if failure */
+	EI_ETYPE_ERRNO,		/* Return -ERRNO if failure */
+	EI_ETYPE_ERRNO_NULL,	/* Return -ERRNO or NULL if failure */
+	EI_ETYPE_TRUE,		/* Return true if failure */
+};
+
+struct error_injection_entry {
+	unsigned long	addr;
+	int		etype;
+};
+
+struct pt_regs;
+
+#ifdef CONFIG_FUNCTION_ERROR_INJECTION
+/*
+ * Whitelist generating macro. Specify functions which can be error-injectable
+ * using this macro. If you unsure what is required for the error-injectable
+ * functions, please read Documentation/fault-injection/fault-injection.rst
+ * 'Error Injectable Functions' section.
+ */
+#define ALLOW_ERROR_INJECTION(fname, _etype)				\
+static struct error_injection_entry __used				\
+	__section("_error_injection_whitelist")				\
+	_eil_addr_##fname = {						\
+		.addr = (unsigned long)fname,				\
+		.etype = EI_ETYPE_##_etype,				\
+	}
+
+void override_function_with_return(struct pt_regs *regs);
+#else
+#define ALLOW_ERROR_INJECTION(fname, _etype)
+
+static inline void override_function_with_return(struct pt_regs *regs) { }
+#endif
+#endif
+
+#endif /* _ASM_GENERIC_ERROR_INJECTION_H */