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, 45 insertions, 0 deletions

diff --git a/fs/lockd/netlink.c b/fs/lockd/netlink.c
new file mode 100644
index 000000000..880c42b4f
--- /dev/null
+++ b/fs/lockd/netlink.c
@@ -0,0 +1,45 @@
+// SPDX-License-Identifier: ((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause)
+/* Do not edit directly, auto-generated from: */
+/*	Documentation/netlink/specs/lockd.yaml */
+/* YNL-GEN kernel source */
+/* To regenerate run: tools/net/ynl/ynl-regen.sh */
+
+#include <net/netlink.h>
+#include <net/genetlink.h>
+
+#include "netlink.h"
+
+#include <uapi/linux/lockd_netlink.h>
+
+/* LOCKD_CMD_SERVER_SET - do */
+static const struct nla_policy lockd_server_set_nl_policy[LOCKD_A_SERVER_UDP_PORT + 1] = {
+	[LOCKD_A_SERVER_GRACETIME] = { .type = NLA_U32, },
+	[LOCKD_A_SERVER_TCP_PORT] = { .type = NLA_U16, },
+	[LOCKD_A_SERVER_UDP_PORT] = { .type = NLA_U16, },
+};
+
+/* Ops table for lockd */
+static const struct genl_split_ops lockd_nl_ops[] = {
+	{
+		.cmd		= LOCKD_CMD_SERVER_SET,
+		.doit		= lockd_nl_server_set_doit,
+		.policy		= lockd_server_set_nl_policy,
+		.maxattr	= LOCKD_A_SERVER_UDP_PORT,
+		.flags		= GENL_ADMIN_PERM | GENL_CMD_CAP_DO,
+	},
+	{
+		.cmd	= LOCKD_CMD_SERVER_GET,
+		.doit	= lockd_nl_server_get_doit,
+		.flags	= GENL_CMD_CAP_DO,
+	},
+};
+
+struct genl_family lockd_nl_family __ro_after_init = {
+	.name		= LOCKD_FAMILY_NAME,
+	.version	= LOCKD_FAMILY_VERSION,
+	.netnsok	= true,
+	.parallel_ops	= true,
+	.module		= THIS_MODULE,
+	.split_ops	= lockd_nl_ops,
+	.n_split_ops	= ARRAY_SIZE(lockd_nl_ops),
+};