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, 134 insertions, 0 deletions

diff --git a/lib/uuid.c b/lib/uuid.c
new file mode 100644
index 000000000..128a51f18
--- /dev/null
+++ b/lib/uuid.c
@@ -0,0 +1,134 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Unified UUID/GUID definition
+ *
+ * Copyright (C) 2009, 2016 Intel Corp.
+ *	Huang Ying <ying.huang@intel.com>
+ */
+
+#include <linux/kernel.h>
+#include <linux/ctype.h>
+#include <linux/errno.h>
+#include <linux/export.h>
+#include <linux/hex.h>
+#include <linux/uuid.h>
+#include <linux/random.h>
+
+const guid_t guid_null;
+EXPORT_SYMBOL(guid_null);
+const uuid_t uuid_null;
+EXPORT_SYMBOL(uuid_null);
+
+const u8 guid_index[16] = {3,2,1,0,5,4,7,6,8,9,10,11,12,13,14,15};
+const u8 uuid_index[16] = {0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15};
+
+/**
+ * generate_random_uuid - generate a random UUID
+ * @uuid: where to put the generated UUID
+ *
+ * Random UUID interface
+ *
+ * Used to create a Boot ID or a filesystem UUID/GUID, but can be
+ * useful for other kernel drivers.
+ */
+void generate_random_uuid(unsigned char uuid[16])
+{
+	get_random_bytes(uuid, 16);
+	/* Set UUID version to 4 --- truly random generation */
+	uuid[6] = (uuid[6] & 0x0F) | 0x40;
+	/* Set the UUID variant to DCE */
+	uuid[8] = (uuid[8] & 0x3F) | 0x80;
+}
+EXPORT_SYMBOL(generate_random_uuid);
+
+void generate_random_guid(unsigned char guid[16])
+{
+	get_random_bytes(guid, 16);
+	/* Set GUID version to 4 --- truly random generation */
+	guid[7] = (guid[7] & 0x0F) | 0x40;
+	/* Set the GUID variant to DCE */
+	guid[8] = (guid[8] & 0x3F) | 0x80;
+}
+EXPORT_SYMBOL(generate_random_guid);
+
+static void __uuid_gen_common(__u8 b[16])
+{
+	get_random_bytes(b, 16);
+	/* revision 0b10 */
+	b[8] = (b[8] & 0x3F) | 0x80;
+}
+
+void guid_gen(guid_t *lu)
+{
+	__uuid_gen_common(lu->b);
+	/* version 4 : random generation */
+	lu->b[7] = (lu->b[7] & 0x0F) | 0x40;
+}
+EXPORT_SYMBOL_GPL(guid_gen);
+
+void uuid_gen(uuid_t *bu)
+{
+	__uuid_gen_common(bu->b);
+	/* version 4 : random generation */
+	bu->b[6] = (bu->b[6] & 0x0F) | 0x40;
+}
+EXPORT_SYMBOL_GPL(uuid_gen);
+
+/**
+ * uuid_is_valid - checks if a UUID string is valid
+ * @uuid:	UUID string to check
+ *
+ * Description:
+ * It checks if the UUID string is following the format:
+ *	xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx
+ *
+ * where x is a hex digit.
+ *
+ * Return: true if input is valid UUID string.
+ */
+bool uuid_is_valid(const char *uuid)
+{
+	unsigned int i;
+
+	for (i = 0; i < UUID_STRING_LEN; i++) {
+		if (i == 8 || i == 13 || i == 18 || i == 23) {
+			if (uuid[i] != '-')
+				return false;
+		} else if (!isxdigit(uuid[i])) {
+			return false;
+		}
+	}
+
+	return true;
+}
+EXPORT_SYMBOL(uuid_is_valid);
+
+static int __uuid_parse(const char *uuid, __u8 b[16], const u8 ei[16])
+{
+	static const u8 si[16] = {0,2,4,6,9,11,14,16,19,21,24,26,28,30,32,34};
+	unsigned int i;
+
+	if (!uuid_is_valid(uuid))
+		return -EINVAL;
+
+	for (i = 0; i < 16; i++) {
+		int hi = hex_to_bin(uuid[si[i] + 0]);
+		int lo = hex_to_bin(uuid[si[i] + 1]);
+
+		b[ei[i]] = (hi << 4) | lo;
+	}
+
+	return 0;
+}
+
+int guid_parse(const char *uuid, guid_t *u)
+{
+	return __uuid_parse(uuid, u->b, guid_index);
+}
+EXPORT_SYMBOL(guid_parse);
+
+int uuid_parse(const char *uuid, uuid_t *u)
+{
+	return __uuid_parse(uuid, u->b, uuid_index);
+}
+EXPORT_SYMBOL(uuid_parse);