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, 70 insertions, 0 deletions

diff --git a/net/ipv4/protocol.c b/net/ipv4/protocol.c
new file mode 100644
index 000000000..691397994
--- /dev/null
+++ b/net/ipv4/protocol.c
@@ -0,0 +1,70 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * INET		An implementation of the TCP/IP protocol suite for the LINUX
+ *		operating system.  INET is implemented using the  BSD Socket
+ *		interface as the means of communication with the user level.
+ *
+ *		INET protocol dispatch tables.
+ *
+ * Authors:	Ross Biro
+ *		Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
+ *
+ * Fixes:
+ *		Alan Cox	: Ahah! udp icmp errors don't work because
+ *				  udp_err is never called!
+ *		Alan Cox	: Added new fields for init and ready for
+ *				  proper fragmentation (_NO_ 4K limits!)
+ *		Richard Colella	: Hang on hash collision
+ *		Vince Laviano	: Modified inet_del_protocol() to correctly
+ *				  maintain copy bit.
+ */
+#include <linux/cache.h>
+#include <linux/module.h>
+#include <linux/netdevice.h>
+#include <linux/spinlock.h>
+#include <net/protocol.h>
+
+struct net_protocol __rcu *inet_protos[MAX_INET_PROTOS] __read_mostly;
+EXPORT_SYMBOL(inet_protos);
+const struct net_offload __rcu *inet_offloads[MAX_INET_PROTOS] __read_mostly;
+EXPORT_SYMBOL(inet_offloads);
+
+int inet_add_protocol(const struct net_protocol *prot, unsigned char protocol)
+{
+	return !cmpxchg((const struct net_protocol **)&inet_protos[protocol],
+			NULL, prot) ? 0 : -1;
+}
+EXPORT_SYMBOL(inet_add_protocol);
+
+int inet_add_offload(const struct net_offload *prot, unsigned char protocol)
+{
+	return !cmpxchg((const struct net_offload **)&inet_offloads[protocol],
+			NULL, prot) ? 0 : -1;
+}
+EXPORT_SYMBOL(inet_add_offload);
+
+int inet_del_protocol(const struct net_protocol *prot, unsigned char protocol)
+{
+	int ret;
+
+	ret = (cmpxchg((const struct net_protocol **)&inet_protos[protocol],
+		       prot, NULL) == prot) ? 0 : -1;
+
+	synchronize_net();
+
+	return ret;
+}
+EXPORT_SYMBOL(inet_del_protocol);
+
+int inet_del_offload(const struct net_offload *prot, unsigned char protocol)
+{
+	int ret;
+
+	ret = (cmpxchg((const struct net_offload **)&inet_offloads[protocol],
+		       prot, NULL) == prot) ? 0 : -1;
+
+	synchronize_net();
+
+	return ret;
+}
+EXPORT_SYMBOL(inet_del_offload);