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, 95 insertions, 0 deletions

diff --git a/net/phonet/sysctl.c b/net/phonet/sysctl.c
new file mode 100644
index 000000000..463a74a27
--- /dev/null
+++ b/net/phonet/sysctl.c
@@ -0,0 +1,95 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * File: sysctl.c
+ *
+ * Phonet /proc/sys/net/phonet interface implementation
+ *
+ * Copyright (C) 2008 Nokia Corporation.
+ *
+ * Author: Rémi Denis-Courmont
+ */
+
+#include <linux/seqlock.h>
+#include <linux/sysctl.h>
+#include <linux/errno.h>
+#include <linux/init.h>
+
+#include <net/sock.h>
+#include <linux/phonet.h>
+#include <net/phonet/phonet.h>
+
+#define DYNAMIC_PORT_MIN	0x40
+#define DYNAMIC_PORT_MAX	0x7f
+
+static DEFINE_SEQLOCK(local_port_range_lock);
+static int local_port_range_min[2] = {0, 0};
+static int local_port_range_max[2] = {1023, 1023};
+static int local_port_range[2] = {DYNAMIC_PORT_MIN, DYNAMIC_PORT_MAX};
+static struct ctl_table_header *phonet_table_hrd;
+
+static void set_local_port_range(int range[2])
+{
+	write_seqlock(&local_port_range_lock);
+	local_port_range[0] = range[0];
+	local_port_range[1] = range[1];
+	write_sequnlock(&local_port_range_lock);
+}
+
+void phonet_get_local_port_range(int *min, int *max)
+{
+	unsigned int seq;
+
+	do {
+		seq = read_seqbegin(&local_port_range_lock);
+		if (min)
+			*min = local_port_range[0];
+		if (max)
+			*max = local_port_range[1];
+	} while (read_seqretry(&local_port_range_lock, seq));
+}
+
+static int proc_local_port_range(const struct ctl_table *table, int write,
+				 void *buffer, size_t *lenp, loff_t *ppos)
+{
+	int ret;
+	int range[2] = {local_port_range[0], local_port_range[1]};
+	struct ctl_table tmp = {
+		.data = &range,
+		.maxlen = sizeof(range),
+		.mode = table->mode,
+		.extra1 = &local_port_range_min,
+		.extra2 = &local_port_range_max,
+	};
+
+	ret = proc_dointvec_minmax(&tmp, write, buffer, lenp, ppos);
+
+	if (write && ret == 0) {
+		if (range[1] < range[0])
+			ret = -EINVAL;
+		else
+			set_local_port_range(range);
+	}
+
+	return ret;
+}
+
+static struct ctl_table phonet_table[] = {
+	{
+		.procname	= "local_port_range",
+		.data		= &local_port_range,
+		.maxlen		= sizeof(local_port_range),
+		.mode		= 0644,
+		.proc_handler	= proc_local_port_range,
+	},
+};
+
+int __init phonet_sysctl_init(void)
+{
+	phonet_table_hrd = register_net_sysctl(&init_net, "net/phonet", phonet_table);
+	return phonet_table_hrd == NULL ? -ENOMEM : 0;
+}
+
+void phonet_sysctl_exit(void)
+{
+	unregister_net_sysctl_table(phonet_table_hrd);
+}