From e873c74132f0c5f1452816cd9bb26208f0bba1e1 Mon Sep 17 00:00:00 2001
From: Shivank Garg <shivankg@amd.com>
Date: Sat, 22 Aug 2026 19:22:05 +0000
Subject: dmaengine: fix use-after-free in dma_chan_put() and
 dma_release_channel()

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>
---
 lib/decompress.c | 83 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 83 insertions(+)
 create mode 100644 lib/decompress.c

(limited to 'lib/decompress.c')

diff --git a/lib/decompress.c b/lib/decompress.c
new file mode 100644
index 000000000..778547158
--- /dev/null
+++ b/lib/decompress.c
@@ -0,0 +1,83 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * decompress.c
+ *
+ * Detect the decompression method based on magic number
+ */
+
+#include <linux/decompress/generic.h>
+
+#include <linux/decompress/bunzip2.h>
+#include <linux/decompress/unlzma.h>
+#include <linux/decompress/unxz.h>
+#include <linux/decompress/inflate.h>
+#include <linux/decompress/unlzo.h>
+#include <linux/decompress/unlz4.h>
+#include <linux/decompress/unzstd.h>
+
+#include <linux/types.h>
+#include <linux/string.h>
+#include <linux/init.h>
+#include <linux/printk.h>
+
+#ifndef CONFIG_DECOMPRESS_GZIP
+# define gunzip NULL
+#endif
+#ifndef CONFIG_DECOMPRESS_BZIP2
+# define bunzip2 NULL
+#endif
+#ifndef CONFIG_DECOMPRESS_LZMA
+# define unlzma NULL
+#endif
+#ifndef CONFIG_DECOMPRESS_XZ
+# define unxz NULL
+#endif
+#ifndef CONFIG_DECOMPRESS_LZO
+# define unlzo NULL
+#endif
+#ifndef CONFIG_DECOMPRESS_LZ4
+# define unlz4 NULL
+#endif
+#ifndef CONFIG_DECOMPRESS_ZSTD
+# define unzstd NULL
+#endif
+
+struct compress_format {
+	unsigned char magic[2];
+	const char *name;
+	decompress_fn decompressor;
+};
+
+static const struct compress_format compressed_formats[] __initconst = {
+	{ .magic = {0x1f, 0x8b}, .name = "gzip", .decompressor = gunzip },
+	{ .magic = {0x1f, 0x9e}, .name = "gzip", .decompressor = gunzip },
+	{ .magic = {0x42, 0x5a}, .name = "bzip2", .decompressor = bunzip2 },
+	{ .magic = {0x5d, 0x00}, .name = "lzma", .decompressor = unlzma },
+	{ .magic = {0xfd, 0x37}, .name = "xz", .decompressor = unxz },
+	{ .magic = {0x89, 0x4c}, .name = "lzo", .decompressor = unlzo },
+	{ .magic = {0x02, 0x21}, .name = "lz4", .decompressor = unlz4 },
+	{ .magic = {0x28, 0xb5}, .name = "zstd", .decompressor = unzstd },
+	{ /* sentinel */ }
+};
+
+decompress_fn __init decompress_method(const unsigned char *inbuf, long len,
+				const char **name)
+{
+	const struct compress_format *cf;
+
+	if (len < 2) {
+		if (name)
+			*name = NULL;
+		return NULL;	/* Need at least this much... */
+	}
+
+	pr_debug("Compressed data magic: %#.2x %#.2x\n", inbuf[0], inbuf[1]);
+
+	for (cf = compressed_formats; cf->name; cf++)
+		if (!memcmp(inbuf, cf->magic, 2))
+			break;
+
+	if (name)
+		*name = cf->name;
+	return cf->decompressor;
+}
-- 
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